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By Douglas R. Cook

The discovery of the gold deposits of the Jerritt Canyon district, with proven recoverable reserves in excess of 67.6 Mg (2.4 million oz) of gold, has contributed greatly to the tremendous resurgence in exploration for disseminated gold deposits in Nevada and throughout the west. The Jerritt Canyon project, including the Bell mine, is a 70130 joint venture between Freeport Gold Co. and FMC Gold Corp., both of which are wholly owned affiliates of the respective parent companies, Freeport-McMoRan Inc. and FMC Corp. The Jerritt Canyon district is located in the center of the Independence Mountains in north-central Elko County, Nevada, approximately 48 km (30 miles) northeast of the Carlin gold mine and 68 km (42 miles) north of Elko. Although the discovery of a commercial gold mine at Jerritt resulted from Freeport's exploration activities, the initial identification of a gold prospect in this area was a consequence of a program by FMC in the search for antimony. Their program was, in part, based on data in the Nevada Bureau of Mines Bulletin 61, "Antimony Deposits in Nevada." Work on the property began in 197 1 with geologic mapping followed by sampling and geochemical analyses. FMC geologists, including Robert Hawkins, Russell Hayden, and Hal Hurst recognized the striking similarity of the area to the geologic environment of Newmont's nearby Carlin gold deposit and soon focused on the gold potential. Increases in the price of gold served to stimulate interest and support for the exploration program. Geochemical samples were collected and analyzed for gold and trace elements usually associated with gold. A strong gold anomaly was found on the North Fork of Jerritt Canyon, which was called the Alchem anomaly. Drill-testing of this anomaly in 1973 revealed significant grades and thicknesses of gold mineralization in the lower portion of the Roberts Mountain formation. This initial discovery and subsequent close-spaced drilling proved the existence of several small pods of low-grade, gold-bearing material which cropped out at their up-dip edges, causing the surface anomaly. The mineralization was very encouraging, but was not, by itself, of economic importance from the standpoint of either grade or tonnage. Freeport Exploration Co. established a district office in Reno in late 1974 with responsibilities for exploration of hard minerals in the Basin and Range Province. Emphasis of the program was directed to the discovery of precious metal deposits. Enfield Bell, as District Manager for this new office, was particularly interested in the Independence Mountains and when the opportunity for a joint venture with FMC became available in 1976, it was aggressively pursued. Enfield Bell and David Stevens evaluated the FMC data and with the support of management formulated a bid in competition with 23 other companies. Freeport was selected by FMC as partner and a joint venture agreement was successfully negotiated. In mid-summer of 1976, Freeport Exploration Co. began an expanded program of detailed mapping and geochemical sampling under the direction of Bell and Stevens that led to new interpretations of the structural and alteration patterns. Hawkins' contribution during this period must be recognized since he not only was one of the original geologists assigned to the antimony and subsequently the gold investigations, but shortly after the start of the joint venture exploration, he was hired by Freeport Exploration Co. as the project geologist for the venture. Hawkins had studied the central Independence Mountains for his thesis and his understanding of the regional geology provided an excellent background for the continued exploration of the gold de- posits. His interpretation of the structure in the vicinity of the Alchem anomaly was of significant help in the Freeport exploration program. Drilling, based on this new under- standing of the geology, revealed the edge of the Marlboro Canyon ore body, which is now being exploited in the Bell mine. Although a classic bullseye geochemical target led to the discovery of the Alchem mineralization, the bulk of the reserves known today in the Marlboro Canyon area lay

Jan 1, 1985

By A. M. Gaudin, J. G. Morrow

FLOTATION requires the existence of a definite contact angle. This contact angle, the surface tension of the solution, and adsorption at the solid-fluid interface are quantitatively related. Adsorption of dodecylammonium acetate on hematite was measured for a wide range of concentrations of reagent in solution. Similar measurements for quartz have already been made. Contact angle measurements were then made on polished surfaces of hematite and of quartz immersed in aqueous dodecylammonium acetate solutions, and a functional relationship was sought between adsorption density at the mineral-solution interface and the contact angle. Finally, the surface tension of the aqueous amine acetate solutions was measured. These data were combined to give an evaluation of the work of adhesion for the three-phase system. Specular hematite was crushed and then ground dry in a laboratory porcelain mill, with flint pebbles, to pass a 200-mesh screen. The ground product was sized in a Haultain infrasizer, and one of the granular sizes (cone No. 3) was used in all adsorption tests. A hand magnet was used to remove magnetite and abraded iron. Quartz was removed in a Frantz isodynamic magnetic separator. The purified hematite was leached in aqua regia, washed with distilled water until the washings appeared free of electrolyte by conductance measurement, dried in a low-temperature oven, and stored in a pyrex container. The specific surface of the closely sized hematite was determined by the krypton gas adsorption method.' Three measurements gave an average value of 1350 sq cm per g. Chemical analysis showed Fe -69.37 pct, insol = 0.72 pct. The quartz used in the flotation tests had been prepared by Chang" for an earlier investigation. Demineralized distilled water was used for all test solutions. Dissolved salt content was of the order of 0.03 ppm, expressed in terms of sodium chloride, as estimated from conductance measurements. Dodecylammonium acetate was obtained from Armour & CO. in two forms, the unmarked compound and a preparation marked by carbon 14 in the hydrocarbon chain of the aminium ion. Specific activity of the active salt was 0.134 millicurie per g. The important physico-chemical constants for the primary amine salt have been reviewed by de Bruyn. The calculated effect of hydrolysis of amine salt on pH of aqueous solutions and the effect of pH on the distribution ratio of the alkylammonium ion to free amine are of particular interest. All other chemicals used in this investigation were of analytical reagent grade. A column method' was used for adsorption work. Attainment of equilibrium distribution in the adsorption column depends on the solid-solution contact time, hence upon the volume of solution passed. It was assumed that contact time required for equilibrium would be a maximum for the lowest reagent concentrations. On this premise it was demonstrated experimentally that the passage of 500 ml of solution through the mineral bed was adequate. An aliquot (1 to 5 cc) of the solution to be analyzed was transferred to a small pyrex cup and allowed to evaporate to dryness at room temperature; 4 or 5 mg of unmarked amine acetate were added to the dried sample and the cup and its contents were transferred to the combustion system for analysis. Evaporation at room temperature must be emphasized, as even slightly elevated temperatures result in loss of reagent. A laboratory model G Beckman pH meter equipped with a glass electrode was used to measure pH of amine acetate solutions. The technique of internal gas counting of radioactive carbon dioxide in a Geiger-Muller counter was used. Developed originally by Brown and Miller,- his method was adapted to the analysis of carbon-14 marked flotation reagents by Chang, de Bruyn, and Bloecher. nalytica1 method and procedures have been described in detail by Bloecher.' Contact angles were measured by the captive-bubble technique." The mineral specimens were carefully selected to avoid cracks and inclusions of other minerals. All specimens were mounted in plastic and polished to produce a smooth surface. The final polishing and contact-angle measuring

Jan 1, 1955

By H. H. Podgurski, F. N. Davis

In silver alloys containing less than 0.2 wt pet Cu. the reaction 9 + 1/2 0, = CuO(s) was found to proceed to equilibrium between 700o and 808oC. From measurements of the equilibrium dissociation pressures of the CuO at several temperatures, the differential heat of solution and the activity coeflicients for copper in silver were calculated. These values were found to be in reasonable agreement with those calculated from data appearing in the literature. A metastable "copper oxide" with an atom ratio of oxygen to copper as high as 1.7 was formed by internal oxidation at 300°C of these same dilute Ag-Cu alloys. No anomalous behavior was noted in the temperature dependence of oxygen solubility in silver. The solubility minima between 300" and 800°C reported several years ago can be accounted for, at least in part, by reactions with trace impurities, such as copper. Cold-worked siloer exhibits an enhanced permeability to oxygen. THIS investigation was undertaken because of our interest in interactions between solute and lattice defects in metals. The reason for the choice of the O-Ag system for study is the anomaly in the solubility of oxygen in silver reported by Steacie and Johnson1 in 1926, specifically that isobars between 100 and 800 Torr show solubility minima at 400°C. It was also claimed that the copper impurity in the silver was not responsible for the minima. Recently, Eichenauer and Müller2 proposed that surface adsorption might have been responsible for this solubility anomaly, but no adsorption isotherms are available to check the pressure and temperature dependence observed at the low temperatures. Surface-tension measurements on silver made by Buttner, Funk, and udin3 suggest that a considerable fraction of a monolayer of oxygen exists on silver at 922°C and at an oxygen pressure of 150 Torr. To account for the pressure sensitivity reported by Steacie and Johnson1 at 300°C, the oxygen bound to the surface at 922°C cannot be considered relevant; the existence of a surface layer at 300°C characterized by a lower energy of binding would be required to explain the effect. All of our attempts to detect an interaction of this type with surface sites have failed. In this investigation we have not been able to associate the dissolution of oxygen in silver with a dislocation interaction. Evidently, severely cold-worked silver does not contain a sufficient number of trapping -sites for oxygen. Indeed, our work shows that oxidation of trace impurities in the silver was probably responsible for Steacie and Johnson's results. In addition, we have been able to establish the nature of the reaction with copper impurity in silver by thermodynamic considerations. EXPERIMENTAL PROCEDURE Measurements of both the internal oxidation rates and the solubility were made volumetric ally in a system equipped with a gas burette, a mercury manometer, a McLeod Gage, and a mass spectrometer. The silver and the silver-alloy samples were protected from contamination by mercury vapor from our pressure gages by suitably placed refrigerated (-78°C) traps. Silica reaction vessels were employed for experiments performed above 500°C. Spectroscopically pure gases were used in this investigation. The highest-purity silver used in the solubility measurements was 99.999 pet. By chemical analysis 2 ppm of Cu were found in this silver. The two Ag-Cu alloys used in this research were made up to 0.14 and 0.15 wt pet Cu starting with 99.999 pet Ag. An unexpected source of error was discovered in the course of the work. At temperatures near 800°C silver distilled from the hot silica reaction tubes into cooler regions of our system. Although the weight loss of silver from the sample was not important in itself, oxygen was being consumed by the silver distilled into the cooler part of the system to form a stable oxide phase from which the oxygen was not recovered. In a separate experiment conducted to determine the necessary correction, losses between 0.2 and 0.3 cu cm (stp) of 0, in 24 hr were measured at 810°C. On the assumption that the flux of silver from the vessel to form Ag2O de-

Jan 1, 1964

By H. Macpherson

Durhm has a well earned reputation for supplying some of the finest coking caals in the world. The caals, in general, vary in rank from 301 to 501/2. Durham has traditionally produced foundry coke for the major proportion of the foundries in Great Britah. Durham coals can be described as clean, soft coals, which yielded, with the old hand methods of coal getting, low ash small coal because the extraneous shale was normally harder than the coal and occurred in larger pieces. Under these conditions, with a plentiful supply of cheap labor, it used to be sufficient, at most collieries, to hand clean the large sizes of coal which could then be remixed with the untreated small coal to produce carbonization coals, ready for the coke ovens, at under 5 pct ash. With the introduction of mechanical methods of coal mining, the coal gradually required more cleaning. The first method adopted to resolve this problem was the introduction of pneumatic dry cleaners for the small coal. Although such machines had little effect on the fine coal (say below 1/8 in.), they could clean the intermediate sizes of coal. This, coupled with hand cleaning the larger sizes above 1-1/2or 2 in., resulted in a combined run-of-mine mixture below 6 pct ash, capable of maintaining the quality and reputation of the cokes produced. In more recent years, the intensification of mechanization and power loading, coupled with gradual exhaustion of the cleaner seams, has created the need for a more complete method of coal cleaning. This particularly applies in the fine sizes (say below 1/50 in.) which normally vary, under present day conditions, between 15 and 35 pct ash and are much too dirty to be included in the raw state in a carbonization mixture. This pronounced change has been accelerated because legislation controlling the dust conditions of mine airs for the prevention of pneumoconiosis has resulted in tk~e extensive use of water underground and a consequent increase in moisture content of the run-of-milie output. The presence of damp fine coal decreast the efficiency of prescreening and dry cleaners, so that this type of preparation for low ash coking coals is decreasing, although it is still used satisfactorily for industrial coals in the medium ash range. Table I shows the gradual increase in mechanization, the reduction in manpower, the increased use of explosives per ton of coal extraction, and the increase in the proportion of coal cleaned by mechanical means in Great Britain. Although similar figures are not available for Durham Div. until after the date of nationalization of the coal industry, it is probable that the increase in mechanical cleaning, particularly by dry cleaners, was more marked in the Durham collieries than elsewhere in the country. As dry clealiers were replaced by coal washeries in the Gritish ccal industry, no special attempts were made to recover the slurry, with the result that large outflows of dirty water were allowed, deposits of slurry came in to lagoons and neighboring streams, and a proportion of fine material was lost from the coking coal. This position, coupled with the higher moisture of the washed coking coal, resulted in adverse effects on coke oven throughputs and coke quality. It is now realized that the natural coal fines are an essential ingredient of coking coals in obtaining the correct coke structure in metallurgical cokes. This, together with economic pressure, led to the introduction of flocculation and filtration plants for the recovery of slurries, and later, when the ash contelits of the filter cakes were too high, to the introduction of froth flotation equipment. After this position had been reached, the tailings from the froth flotation pIants were, in many cases, still allowed to constitute an undesirable effluent. Recent legislation on river pollution has changed this picture; it is now necessary to provide a circuit which is completely closed so far as solids are concerned. The gradual increase in the coal cleaned by wet methods and froth flotation in Durham Div, is shown in Table 11. It is now an accepted feature of new Washeries that. froth flotation should be an integral part of the washing process from the initial installation of the plant.

Jan 1, 1962

By O. N. Carlson, H. A. Wilhelm, J. M. Dickinson

On the basis of microscopic studies, melting-point observations, and X-ray analyses, a phase diagram is proposed for the Cb-V system. A complete series of solid solutions is formed with a minimum in the solidus at 1810°C near 35 wt pct Cb. No compounds or intermediate phases were found in the system above 650°C. THERE is an ever increasing need for better structural metals and alloys for use in nuclear reactors. In addition to the normal properties of engineering structural materials, such as high temperature strength, resistance to corrosion, and fabric-abil~ty, the nuclear properties of the material must be considered. In a nuclear reactor it is important to conserve neutrons, so a material which removes these neutrons from the reaction excessively is considered to have unfavorable nuclear properties. In nuclear-reactor design the engineer must have nuclear as well as other data available on alloys in order to make a wise selection of materials. Due to the fact that many of the common structural materials have undesirable nuclear properties, it is vital that new alloys of metals having more favorable nuclear properties be investigated. Columbium and vanadium are both high melting metals, both exhibit resistance to chemical attack, and no great difficulty is encountered in fabricating them into desired shapes. With proper treatment both metals can be cold rolled extensively without failure. In addition they have desirable nuclear properties for certain types of reactors. Therefore, the alloys of columbium and vanadium should be of interest in the atomic energy program. Since an alloy-development program is enhanced by a knowledge of the phase equilibria of the components, this investigation was undertaken to establish the phase diagram for the Cb-V system. According to the Hume-Rothery rules for alloying,' the chemical similarity, crystal structure, and atomic-size factor are favorable for a complete series of solid solutions for this system. Both elements are in the same family of group V of the periodic table and thus are quite similar chemically. The crystal structures of columbium and vanadium are compatible for extensive solid solubility, since both have body-centered-cubic structures. The atomic diameters of columbium and vanadium are 2.85 and 2.62Å, respectively. This difference of slightly more than 8 pct is well within the 15 pct maximum difference allowed for extensive solid solubility. Experimental Procedures Source of Materials: Columbium powder and sheet trimmings were obtained from the Fansteel Metallurgical Corp. According to the manufacturer the metal contains less than 1 pct impurity. An analysis of the metal showed approximately 1800 ppm C in the powder while the sheet trimmings contained less than 500 ppm C. Spectrographic analysis showed minor amounts of Ca, Cr, Fe, Mn, Si, Ti, V, and Zr in both forms of the columbium. No commercial source of vanadium having the ductility and purity desired was available to the authors at the beginning of this investigation. As a result, all of the vanadium used in this study was prepared by the bomb reduction of vanadium pen-toxide with calcium employing the method reported by Long.' Yields of massive vanadium normally were about 80 pct. Chemical analysis of the vanadium prepared in this manner showed the presence of 200 to 500 ppm N and 800 to 1000 ppm C. Minor amounts of Ca, Fe, Mn, Si, Zr, Cr, and Cb were detected by spectrographic analysis. This vanadium metal was ductile and was cold rolled into 5 mil sheet. Annealing was not necessary during this rolling and the metal retained its cold-rolling characteristic after are-melting. Preparation of Alloys: The Cb-V alloys were prepared by melting pieces of vanadium sheet togethel-with columbium in the form of sheet or pellets of powder. The melting was carried out under argon in conventional arc-melting equipment employing a tungsten electrode and a water-cooled copper crucible. Each alloy was remelted three or four times, inverting the alloy after each melting in order to assure complete mixing. Alloys normally were obtained as round flat disks, weighed approximately 70 grams, and had roughly the shape of a disk 1 1/2 in. in diameter and 1/4 in. thick. Half of each alloy

Jan 1, 1955

By Carl Altstetter, Roy Adams

Measurements of enthalpy changes and transformation temperatures me reported for the fcc -hcp marten-sitic transformation in pure cobalt single and multi-variant crystals andpolycrystalline specimens. From these measurements the free-energy difference between the two phases was calculated for both heating and cooling and for repeated cycles through the transformation. For heating of single crystals the average value of enthalpy change was 113 cal per mole but on cooling it was 84 cal per mole. This difference is interpreted in terms of lattice imperfections which are introduced during transformation. A calorimeter suitable for measurement of enthalpy changes of athertnal transformations is described. COBALT exhibits an allotropic phase transformation at around 417°C' where an hcp phase (a = 2.507, c = 4.0686, c/a = 1.6228)~ stable at low temperatures transforms to an fcc phase stable up to 1495°C. The transformation has a hysteresis of about 30°C— the exact magnitude of the hysteresis depending on the number of transformation cycles, grain size, impurity content, and prior treatment.'-6 The athermal character of the transformation and surface relief due to transformation shear indicate that the transformation is martensitic. Pole mechanisms for the transformation have been discussed by Sebilleau and Bibrin, Bilby, Seeger,' and Basinski and Christian. These authors have proposed that the cooling transformation is effected by rotation of a Shockley partial dislocation around a pole dislocation with a screw component of 2a/3(111). Such a rotation would change the stacking of close-packed planes from the abcabc fcc stacking to the ababab hcp stacking sequence. This mechanism would predict a lattice correspondence of {111}fcc~~(0002~cp, have been observed. One would expect the heating transformation to occur similarly, involving dislocation movements on the (0002)hcp. However, a high density of pole dislocations and high dislocation ve- locity are required to account for microscopic observations. Furthermore, the high back stress developed on the Shockley partial dislocation as it rotates toward the sessile dislocation associated with it makes it doubtful that this is in fact the transformation mechanism. A mechanism for spontaneous nucleation of partial dislocations1*l2 seems more reasonable. If a single crystal of cobalt is cycled through the transformation but never heated above 600°C, it will remain single."13 However, if the specimen is heated through the transformation and held for a short time at or above 1000°C before cooling, the cooling transformation usually involves all four {lll}fcc habits, resulting in neighboring orientations of hcp differing by 70.5 deg. This condition is termed multivariance and has been observed by Bibring and sebilleau5 and Nelson and ~ltstetter.' The latter authors used single crystals of cobalt grown in an electron beam zone refiner. They proposed that the strongly directional cooling caused the initial cooling transformation to occur on the {lll)fcc most nearly perpendicular to the temperature gradient. Transformation shear on one set of {lll}fcc planes immobilized dislocations on the other {lll}fcc planes involved in the initial transformation. Since there is only one (0002)hcp plane orientation, the product of subsequent heating transformations could have no more than two variants—the original fcc orientation or its twin. If, however, the specimen was annealed at a high temperature, such as 1000°C, there would be relaxation of dislocations into low-energy configurations, and in the absence of a sharp temperature gradient transformation on all four (111 Ifcc planes could occur. If a dislocation mechanism is responsible for the transformation, the perfection of the lattice should affect the reversibility of the transformation. Mutual constraints of neighboring grains in polycrystalline material would inhibit dislocation movement resulting in increasingly sluggish transformation. Indeed, Nelson and Altstetter found the M, to decrease and the A, to increase in going from single crystals to multi-variant specimens to polycrystals. The effect is enhanced by decreasing the grain size of a solid specimen or a powder.6'14 Data on the free-energy difference necessary to initiate the transformation gives information about the driving force of the transformation. This is an important consideration in the understanding of the transformation mechanism. The free-energy change associated with the transformation of the hcp phase to the fcc phase at some temperature T different from the equi-

Jan 1, 1969

By T. L. Joseph, G. Bitsianes

THE layered structure of partially reduced iron ore was described in a previous paper.' Reduction by hydrogen was found to take place at well-defined interfaces between layers of the solid phases. In the present investigation, a detailed study was made of the wiistite phase that had formed during the partial reduction of a cylindrical compact of chemically pure hematite. An unusually wide band of wiistite permitted a rather detailed study of this phase. The specimen was made from Baker's C.P. hematite in the form of a cylinder 1.5 cm in diameter and 1.8 cm long. A dense ore structure with about 6 pct porosity was attained by heating the specimen in air at 1100°C for 3 hr. To confine reduction to the top surface, a ceramic coating was applied to the bottom and sides of the cylindrical compact. The specimen was then partially reduced in hydrogen at 850°C and subjected to a coordinated sequence of macro-, micro-, and X-ray examinations. A section of the partially reduced cylinder is shown in the macrograph, Fig. 1. Four layers consisting of metallic iron, wustite, magnetite, and unreduced hematite are clearly shown. The effort to force reduction to proceed downward in topochemi-cal fashion was only partly successful, as some reduction occurred along one side and bottom of the cylinder. A rather wide layer of dark wustite phase had formed, however, and permitted sampling for X-ray studies as indicated. To supplement previous work and to study the wustite layer in more detail, ten separate layers were removed for X-ray examination. Broad and diffuse patterns were obtained with the as-filed powders, especially with those of iron and wiistite, and the condition indicated a cold-working and variable composition effect within the respective layers. This condition was corrected by annealing the entire series of powders at an appropriate temperature. For the annealing treatment, the ten powder samples were wrapped in silver foil, sealed under vacuum in small quartz tubes, and heated at 750°C for 16 hr. The specimens were then drastically quenched in cold water to preserve the annealed condition. These annealed specimens were X-rayed in turn and the compiled patterns are shown in Fig. 2. The standard patterns for iron and its oxides have been interjected at appropriate positions for purposes of comparison and phase identification. All of the patterns obtained were clearcut and concise so that positive identifications could be made for all of the phases. The outermost layers A, B, and C were composed almost entirely of iron with a small amount of wiistite being detectable at the X-ray limit of phase detection. Layer D from the iron-wustite interface showed both of these phases. The next four layers E, F, G, and H were all in the dark phase band which had been tentatively identified as wustite by the macroexamination, Fig. 1. The diffraction data with their single-phase patterns of wiistite for these layers checked the visual evidence. Continuing the X-ray analyses after layer H, the macrograph (Fig. 1) shows that layer I came largely from the magnetite zone but included some fringes of the wiistite-magnetite interface. The diffraction pattern for the sample confirmed this observation. Layer J came from the unreduced core of the specimen and its diffraction pattern indicated a preponderance of hematite phase. The reduction behavior of synthetic compacts has thus been found to be similar to natural dense iron ore. The previous results were supplemented with measurements of the diffraction films and calculations of the respective unit parameters. These X-ray data are summarized in Table I and offer some interesting correlations as to the compositions of the various phases undergoing reduction. The iron layers that were analyzed gave lattice parameters close to that of pure iron at 2.8664A. Evidently this iron was present in layers A through D as a pure phase with little or no oxygen dissolved in its lattice. With the wiistite layers an entirely different situation prevailed in that there was a definite and

Jan 1, 1955

By T. Seldenrath

In the development of a fluid -operated hammer drill' for accelerated penetration of hard rock formations in oil wells, a research investigation was conducted to evaluate the percussion effects obtained with different design characteristics and to determine the possibilities of percussion in the low frequency range. Tests were conducted on granite blocks and comparable impact forces were measured with a load cell under selected test conditions. These full-scale laboratory tests provided an evaluation of the effectiveness of percussion which was further supported by actual downhole field performance. While much pertinent data have been presented by other investigators the method of evaluation described in this article resulted in good correlation between laboratory and field performance and may be applicable in other low frequency percussion developments. EXPERIMENTAL METHOD For these tests the bit was held stationary and the test block was rotated and forced upward against the bit by a hydraulically-lifted rotary table. "Weight on bit" was calculated from pressure readings on the fluid system of the lifting cylinders—corrected for tare and friction. Percussion was obtained with several tubular hammers of different weights up to 320 lb. These were lifted mechanically and allowed to drop by gravity from various heights onto a slidably-mounted bit sub or "floating anvil" for calibration of the load cell response with known kinetic energy of the hammers. During evaluation of percussion effects, the hammers were hydraulically operated to provide a range of percussion frequencies up to 1,020 blows per minute delivered to the anvil. To obtain comparable test readings, the load cell of the strain gauge type, was attached to the bottom of the anvil or bit sub in place of the bit. The load cell rested on a typical granite test block mounted on the drilling table. The latter was hydraulically supported as in the actual drilling operation. The effect of support resistance was the same for all tools when calibrating. Impact forces so determined werethusdirectly comparable with one another for the purposes of this investigation. When a roller bit was substituted for the load cell for actual drilling, the impact force would probably be reduced due to the resiliency of the bit body, legs. cones and teeth and the penetration of the teeth into the rock. However, since the bits and rock specimens were uniform in these tests, an evaluation of actual tool performance, in terms of parameters previously determined with the load cell at the selected standard conditions of calibration, proved satisfactory. Throughout these tests, 8¾-in. standard tricone, hard rock toothed roller bits and carbide-insert roller bits were used. Rotary speeds were 50 and 100 rpm; static weight on bit was applied up to 40,000 Ib, and percussion frequencies up to 1,020 blows per minute were available. During this investigation it was found that toothed bits on which the teeth had developed flat ends about 3/16 in. wide did not change appreciably for the duration of a test. Hence, all toothed bits used in this study were in this condition. Conventional reference curves obtained in these tests show that increasing weight on hit by 2:1 yielded an increased penetration rate of approximately 2.7:1, while an increase in rotary speed of 2:1 netted an increased penetration rate of roughly 1.7:l. Results are thus of the same order as those reported for hard rock drilling by other investigators." CALIBRATION Under the selected standard test conditions previously described, with the lifting table hydraulically supported, and the anvil interposed between hammer and load cell, the hammers were dropped from known heights. Thus, with the kinetic energy of the hammer known, the corresponding maximum impact force shown by the cell was determined. (It may be of passing interest to note here that special drop tests with the hammers showed that no appreciable reduction in impact force resulted from introduction of the anvil or hit sub.) From these calibrations, it was possible to determine the theoretical kinetic energy available in the hammer from the maximum impact force shown by the load cell while operat-

By N. J. Grant, D. Carne, J. B. Seabrook

IT is unnecessary to review much of the literature on hydrogen embrittlement of steel since several excellent reviews and bibliographies exist.1-3 Hot acid pickling and cathodic charging have been known to cause hydrogen embrittlement of steel and have been used as laboratory methods to charge steels with hydrogen.4-8 Experimental Procedure The problem of prime concern in all instances, except in the work of Sims and coworkers,10 is that at no time was there a definite known hydrogen value reported which could be related to a particular value of the degree of embrittlement. It was the purpose of this research to determine the relationship between hydrogen content and degree of em-brittlement quantitatively. The 1020 stock used for the specimens was hot-rolled 7/16 in. diam rod of the following analysis: 0.19 pct C, 0.40 pct Mn, 0.012 pct P, 0.036 pct S' Vacuum-fusion analyses for nitrogen and oxygen gave 0.014 pct O2 and 0.0011 pct N2. Cathodic charging was used to cause embrittle-ment. The advantages of this method were that no quenching was necessary, the impregnation was reasonably controllable, and representative samples for analysis could be prepared simultaneously with the charging of the tensile bars. Analyses for hydrogen were made in a vacuum-fusion type of apparatus which extracted gas from the samples by fusion in a molten tin-iron bath' This apparatus, which has recently been described in detail elsewhere, will not be discussed here.". " Consecutive samples can be analyzed every 15 min with an accuracy of 0'03 ppm. A A from an electrolytic or pickling bath can be charged for analysis in about 3 min, and analysis completed in 15 min. Samples of as-received 1020 stock were analyzed and found to contain a negligible amount of hydrogen (0.06 ppm). Preliminary pickling and electrolytic charging gave highly variable results. Cold-worked samples showed higher values but ranged from 0.6 to 6.0 ppm of hydrogen. Charging at 90°C gave higher values of charged hydrogen, but troublesome films on many of the specimens resulted. It was not until a few drops of a catalytic poison, prepared from 2 g of yellow phosphorus dissolved in 40 ml of carbon disulphide,8 was added to the electrolytic cell that fairly consistent high values of hydrogen could be charged into the as-received 1020 steel at room temperature. The cell used is sketched in fig. 1. The anode and fixture for the tensile specimens were fastened to the cell cover as shown, and the specimen was screwed in place, centrally located with respect to the anode. At first, anodes of lead and graphite were tried, but they contaminated the electrolyte and gave a slight deposit on the specimen. Later, a platinum wire was used in the form of a uniform helix. A current of 2 amp, corresponding to about 0.5 amp per sq in. of cathode, was used for most specimens. The electrolyte was 4 pct H2SO4 solution. Fig. 1 shows the form of the special tensile bar, the main portion of which was an ordinary 1/4 in. diam, 1 in. gauge length test bar, except that two to four small cylinders of stock were left attached by small links to the bottom end of the tensile bar for the purpose of providing samples for hydrogen analysis. Thus the bars and samples were charged with hydrogen simultaneously and an analysis could be made while the bar was being tested mechanically. Experiments were performed to determine how representative the test cylinders were of the middle of the test bar proper. While the bar center was being analyzed, the small cylinder was stored in dry ice, since it had been shown that such storage prevents loss of hydrogen for many hours.12 The results of these checks are shown in table 1. The checks are very good (0.3 ppm) and indicate that it is permissible to use the small end cylinders to establish the hydrogen content of the tensile test bar proper-

Jan 1, 1951

By Gen-ichi Nakazawa, Masamichi Fujimori, Ichiro Doi

INTRODUCTION The major products of nickel industry in Japan are the electrolytic nickel (E-Ni), the ferro-nickel (Fe-Ni) and the nickel oxide sinter (NOS), totaling in production to 90 - 100 X 103 tons/year in terms of pure nickel content, and sharing approximately 20% for E-Ni, 10% or less for NOS, and the rest for Fe-Ni. The raw materials to be used for these products depend totally upon the imports from abroad; matte, the raw material used in the production of E-Ni, is from Australia and Indonesia; matte for the NOS is from Indonesia and New Caledonia; and garnierite, the raw material for Fe-Ni, is imported in bulk from New Caledonia, Indonesia and the Philippines. This report describes the acquisition of these raw materials, the production processes, trend of supply-demand, problem areas and the measures taken, and so forth, in connection with the nickel industry in Japan. ELECTROLYTIC NICKEL 1. History The nickel industry in Japan began in 1939 by the Sumitomo Metal Mining Co., Ltd. (SMM) with 150 tons E-Ni/month under the blast furnace smelting and the metal anode electrolysis. This was temporarily suspended after the end of last World War II, but resumed in 1952 with garnierite of New Caledonia as a raw material. Since then, the production capacity has been expanded incidentally to the increase of demand. However, since the smelting of garnierite contained about 2% nickel was very costly, the smelting process had been changed to smelt the briquettes of the mixture of garnierite and nickel sulfide concentrate imported from Canada and Australia. In 1975, this smelter was closed, and SMM's nickel refinery used matte from Western Mining Corp. (WMC) of Australia as a raw material. The refining process had been the metal anode one. The crude nickel oxide derived from roasting the high grade nickel matte had been melted and reduced with coke in the electric furnace and cast into anode. In 1970, a new refinery was constructed to produce 1,000 tons Ni/month under the matte anode process, and further, in 1976, the old refinery was converted into the matte anode process, thus resulting in the total production capacity of 1,690 tons Ni/ month today under the matte anode process. Shimura Kako Co., Ltd. began in 1951 to produce a little of E-Ni, and in 1955, they constructed a shaft furnace smelter with New Caledonian garnierite as a raw material to begin the E-Ni production under the matte anode process. Its monthly production reached 400 tons in 1957, but it discontinued its smeltering in 1963 to convert to the matte import from S. Le Nickel, WMC and INCO. In 1979, it changed the source of matte supply from the above to Soroako of Indonesia, discontinued the E-Ni production in 1979, and arranged for a total toll contract with Sumitomo. Meanwhile, SMM has developed a very distingished process for nickel-cobalt separation and refining by a solvent extraction method from nickel and cobalt mixed sulfide generated as a by-product in the nickel recovering process from laterite under the Nicaro process. Nippon Mining Co., Ltd. (NMC) also developed its own process. The plants under these processes were constructed in 1975, with the monthly production capacity of 230 tons of nickel and 130 tons of cobalt by SMM, and 300 tons of nickel and 110 tons of cobalt by NMC. SMM imports the raw material from the Marinduque Mining and Industrial Corp. of the Philippines, while NMC from Queensland Nickel Pty. Ltd. of Australia. 2. Production Status 2.1 Producers and materials Today, SMM holds the monthly E-Ni production capacity of 1,920 tons, of which 1,690 tons are from the matte anode process, and the remaining 230 tons are from the mixed sulfide as a raw material. NMC also uses the mixed sulfide as a raw material for a production of 300 tons/month. [ ] Most of SMM's raw material, nickel matte, is imported from WMC of Australia, partly using the Soroako matte from Indonesia. An example of material analysis is given in Table 1. Matte is a raw material for E-Ni and NOS, and the major sources of matte supply at present are Australian WMC and Indonesian Soroako, occupying ap-

Jan 1, 1982

By C. Y. Ang, C. Wert

Quench aging of supersaturated solid solutions of nitrogen in columbium takes place in reasonable times in the temperature range 300&apos; to 500°C. Changes in internal friction, hardness, and electrical resistivity are found to accompany this change. THERE is practically no detailed information in the literature concerning interstitial solid solutions in either columbium or tantalum. The fact that both of these metals are used extensively commercially in both pure and alloyed states makes studies of their properties of value. While the plan is to study both these metals and their alloys extensively, so far only a small number of measurements have been made. This paper presents data obtained in the initial investigations of columbium. The principal interstitial impurities of columbium are likely to be hydrogen, carbon, oxygen, and nitrogen. The first of these, hydrogen, is outside the scope of internal friction measurements at present and nothing quantitative is known about the initial hydrogen content of the specimens. However, it is believed that it is completely absent after the preliminary heat treatments are carried out. The carbon content of the original samples is low and can be reduced still further during sample preparation. Oxygen is normally present to some extent in columbium and can also be added or removed easily. Nitrogen is also normally present in small amounts and can also be controlled within limits. Since it is not possible yet to remove all the nitrogen from columbium and since it is possible to remove essentially all the oxygen and carbon, initial measurements were made on the alloy system nitrogen in columbium. In this sense then, the alloys are true binary alloys. Little is known about the effects of nitrogen on the physical and metallurgical properties of columbium, so it was necessary to perform some rather elementary measurements on the specimens. These measurements are described briefly in the next section and are discussed in detail in later sections. Scope of the Work That internal friction is associated with diffusion of nitrogen in columbium has been known for some time. It is similar in nature to that for carbon and nitrogen in a-iron. In these latter cases, the information obtained from internal friction has been useful metallurgically.&apos; and it is not too much to expect useful information from similar studies on columbium containing nitrogen. The technique of internal friction measurements is adequately described by Ke2 At a frequency of 1 cps the internal friction peak for nitrogen in columbium occurs at 300°C and that for oxygen at 160°C." So that all the measurements will be meaningful metallurgically, the internal friction has been calibrated by making a measurement of the damping at the two peaks and a measurement of oxygen and nitrogen content by chemical analysis. A comparison of the two gives the following calibration factor: To go from damping capacity expressed in terms of 1/Q to weight percent of oxygen and nitrogen in solid solution in columbium, multiply the peak values of internal friction by about 4 and 3 respectively." Data from which these factors were calculated are presented in Table I. The increase of electrical resistance of columbium caused by the addition of oxygen and nitrogen as interstitial impurities has been quantitatively determined. At room temperature the percentage increase is small for small additions of impurities (<0.1 wt pct); as the temperature is lowered it becomes an increasingly larger factor of the total resistance. An empirical relation has been established to express the resistivity at — 195°C in terms of weight percent of oxygen and nitrogen in solid solution. It is easy to make supersaturated solid solutions of nitrogen in columbium and to observe aging phenomena. The optimum aging temperature, as in the case for carbon and nitrogen in a-iron, occurs at the temperature for which the time necessary for a single place-change in diffusion is about 1 to 10 millisec. This means for nitrogen in columbium that significant property changes should take place for this alloy at about 400" to 500°C in reasonable time intervals. Results of such aging experiments are

Jan 1, 1954

By D. T. Peters, J. C. Bisseliches, J. W. Spretnak

The pain boundary relaxation phenomenon in high-purity copper, 0FHC copper, and a precipitation-hardenable alloy o-fCu-2 uit pct Co has been studied by internal ,friction and elastic aftereffect techniques. The data were analyzed by assuming the broad distribution of relaxation times observed obeys a lognormal distribution law which enables calculation of the relaxation strength. Grain size had no effect on relaxation strength, although the peak width increased with increasing grain size and decreasing temperature. A double grain boundary peak was produced in high-purity copper by annealing to produce secondary recrystallization. The activation energy measured for 99.999 pct Cu is 37.5 * 3 kcal per mol and 46.5 kcal per mole for OFHC copper. A small peak in the Cu-Co alloy at about 220°C at 1 cps was deduced to be the grain boundary peak. Its height increased and its activation energy decreased with increasing aging time. Except for erratic peak positions the observations were consistent with the theory of pain boundary sliding. BEFORE the mechanism of the grain boundary internal friction peak in metals can be satisfactorily explained, the detailed characteristics of the relaxation process must be documented. Of interest are the effect of grain size on relaxation strength, the high-temperature background, and peak width and position. The effect on the grain boundary peak of a precipitate at grain boundaries and of the change in distribution of the particles with aging time must also be explained by any existing or forthcoming theory. The model which has received the most attention was proposed by KG&apos; and zener2 and proposes that the anelastic strain results from sliding of adjacent crystals at grain boundaries. The sliding is limited by the interlocking of grain corners. It follows, according to this model, that the relaxation strength is independent of and the relaxation time is proportional to the grain size. The proportionality between grain size, D, and relaxation time, t, has been confirmed by K&&apos; and Bisseliches . In this case, the internal-friction peaks of various specimens can be superimposed by plotting Q-&apos; as a function of the parameter vD exp H/RT where v is the frequency and H the activation energy. However, the data of Starr et 01.&apos; and Leak6 fit better to a parameter containing D to an exponent near two. A meaningful relationship is not always deducible from the shift of peak temperature with grain size. KG7 demonstrated that a twofold variation in grain size obtained by varying the amount of cold work followed by identical recrystallization anneals will cause a peak shift that is too large to be accounted for even by an exponent of two. Since the decreased grain boundary area existing with a larger grain size is exactly compensated for by an increased sliding distance, the relaxation strength should not decrease with increasing grain size. The height of the internal-friction peak has generally been observed to be rather insensitive to grain size as long as the average grain diameter does not approach the specimen diameter. Exceptions have been reported by Koster, Bangert, and Lang8 for copper, and by Leak6 for iron. The observations for copper could well have been confused by the presence df 0.3 pct0. The possibility that the peaks may simply be increasing in width with increasing grain size and that the relaxation strength, which is proportional to the area under the peak, may remain constant was not examined. his point has been checked in this investigation using high-purity copper. Atomic mechanisms to account for damping by sliding at grain boundaries have been proposed by KG7 and Mott. KG predicts the activation energy to be identical to that for self-diffusion. Mott&apos;s "island" model suggests the activation energy is nL where n is the number of atoms in an island and L is the latent heat of fusion per atom. Other authors have felt that a value equal to the activa-

Jan 1, 1964

By A. V. Bradshaw, R. I. L. Guthrie

The behavior of large bubbles in the size range 4 to 25 cm3, rising through molten silver, has been studied. It was found that rising velocities were equivalent to those in aqueous systems of low viscosity. Mass transfer coefficients for oxygen bubbles dissolving in silver were found to be 0.036 ± 0.007 cm sec-1, being close to those predicted for transfer through the front surface of the spherical cap bubble only. It is suggested that the surface active nature of oxygen in silver could account for the relatively low coefficients obtained. MANY metallurgical processes involve interactions between gas bubbles and liquids. Examples include the removal of carbon monoxide in Open Hearth Steelmak-ing, the removal of sulfur by blowing air through copper matte during converting, and the removal of hydrogen from steel during vacuum degassing or inert gas flushing. The steps involved in such refining processes include; transport of the dissolved species to the bubble interface, adsorption and chemical reaction of the species at the interface, desorption of product molecules from the interface, and transport of product gas into the bulk gas phase of the bubble. It has been concluded1 that all the interfacial steps involved proceed so rapidly at steelmaking temperatures that transport of the solutes, present in the metal, become the important rate controlling factors provided nucleation phenomena are not restrictive. The O-Ag system was chosen for the investigation into gas bubble-molten metal interactions due to the relatively high solubility of oxygen that enables rates of oxygen transfer to be measured from changes in bubble volume. Other advantages of this system include the absence of a stable oxide phase at an oxygen pressure of 1 atm and the relatively low melting point of the metal which permits the use of a metallic container, providing that it is resistant to oxidation. In those metallurgical processes where bubbles have an important influence, bubble volumes are usually greater than 5 cm3. For this reason the present study relates specifically to single large bubbles of oxygen rising in silver. These bubbles adopt the characteristic spherical cap shape similar to that shown in Fig. 1 for a 30 cc bubble rising in water. After an initial investigation to determine the velocities of inert (nitrogen) bubbles rising in molten silver, experiments were carried out with oxygen and the rates of mass transfer between the oxygen bubbles and the silver were measured. EXPERIMENTAL Apparatus. The apparatus, Fig. 2, for containing molten silver, was constructed from "Nimonic 75" Alloy (75 pet Ni, 20 pet Cr, 5 pet Fe, Mn) and provided for the release of single bubbles from an hemispherical cup, situated at the bottom of the column. The cup was turned by translating the rotation of the drive shaft through 90 deg. This was accomplished by the use of a bevelled gear system, and a smooth drive was provided by the lubricating action of the silver on the gears. Since reliable high temperature seals at 1000°C were found to be impracticable, the filling and drive shaft tubes were extended outside the 3.5 kw resistance wire tube furnace, where connections were made using easily accessible O-ring seals. The apparatus remained gas tight to the atmosphere at pressure differentials far in excess of those used. The filling tube was connected via a small bore tube to the differential pressure transducer. Gas could be bubbled into the inverted cup from two i-in. tubes which passed down the inside of the column to preheat the gas. The temperature of the silver was maintained at 1020°C during all experiments. Measurement of Bubble Volume. In order to calculate mass transfer rates, it was necessary to obtain a continuous record of the bubble&apos;s volume during its passage through the column of molten silver. The method adopted for measuring the bubble volume involved closing off the top gas space to the atmosphere prior to each experiment, and recording the variation in gage pressure of this space during the formation and rise of the bubble. Since any change in bubble volume results in an equal change in top space volume, Boyles Gas Law may be applied (for isothermal con-

Jan 1, 1970

By R. J. Charles

SEARCH for a consistent theory to explain the relationship between energy input and size reduction in a comminution process has accumulated, over the years, an enormous amount of plant and laboratory data. Although some correlation of these data has been possible for purposes of engineering design and for the advancement of research in fracture, there is still great need of a means of predicting behaviour of a solid when it is reduced in size by mechanical forces. The best known hypotheses proposed to describe the energy-size reduction relationships in crushing and grinding stem from a common origin. The present article analyzes problems of comminution in the light of the precepts of this origin. Its object is to reconcile points of difference between these well known hypotheses and to present relationships more widely applicable to comminution studies. Theoretical Considerations: Most existing relationships between energy and size reduction of a brittle solid stem from a single, simple, empirical proposition.&apos; Although this proposition can be demonstrated by observation and experiment, no theoretical derivation is yet possible. Mathematically, the proposition may be stated as follows: dE = -Cdx/xn [1] where dE = infinitesimal energy change, C = a constant, dx = infinitesimal size change, x = object size, and n = a constant. Eq. 1 states that the energy required to make a small change in the size of an object is proportional to the size change and inversely proportional to the object size to some power n. No stipulations are placed on the exponent n in either magnitude or sign. In 1867 Rittinger2 postulated that the energy required for size reduction of a solid would be proportional to the new surface area created during the size reduction. As far as can be determined there is as yet no physical basis for Rittinger&apos;s hypothesis. Rittinger&apos;s hypothesis can be stated mathematically as follows: E, = K(oa-a-0 . [2] Er = energy input per unit volume, K = a constant, <ti = initial specific surface, and o2 = final specific surface. In the size reduction of particles of size x, to particles of another smaller size, x2, Eq. 2 becomes the well known relation: ET = K&apos; {l/x2-l/xx) [3] where K&apos; is a constant. Eq. 3 may be arrived at from the proposition given in Eq. 1 by integrating and by assigning a value of 2 to the exponent n. J dE = J - C dx/x2 E = Kt (1x - 1x) where K&apos; = C. In 1885 Kick3 proposed the theory that equivalent amounts of energy should result in equivalent geometrical changes in the sizes of the pieces of a solid. For example, if one unit of energy reduced a number of equal-sized particles to particles of one half the size, then the same amount of energy applied to the particles resulting from the first test should result again in a size reduction of one half or a final size one quarter the original size. The Kick concept may be expressed as follows: Ek = K" log x1/x2 [41 K" = a constant and E, = energy per unit volume. The expression for Kick&apos;s law may be arrived at by again integrating Eq. 1 and in this case assigning a value of 1 to the exponent n. dE= J - C dx/x Eh = - C In {x/x2) = K" log (x,/x,) where K" = 2.3 C. Application of Kick&apos;s and Rittinger&apos;s laws to comminution has met with varied success. Gross and Zimmerley4 and Piret5 have shown that Rittinger&apos;s equation applies under certain conditions of experimentation. Walker and Shaw6 express the belief that in metal turning and shaping and in grinding of both metals and minerals the production of very fine particles (less than lP) follows Kick&apos;s hypothesis, whereas Rittinger&apos;s concept is valid for the size reduction of coarse particles. For the practical case of crushing and grinding, however, neither of the above hypotheses has received general acceptance. Bond&apos; has lately proposed that since neither Kick&apos;s nor Rittinger&apos;s hypotheses seem correct for plant design work, an energy-size reduction relationship somewhere between the two would be more applicable. The fundamental statement of Bond&apos;s work

Jan 1, 1958

By J. H. Swisher

In measuvements of the solubility of nitrogen in fer-rilic Fe-P alloys, tile nitrogen solubility is found to be Less in pIrospliorus-bearing alloys than in pure iron. The reduction in solubility is about 20 pct in a 1.0 wt pct P alloy at 1300°C and about 30 pct in a 0.23 wt pct P alloy at 440°C. Diffusion coefficient measurements at 1150 and 585°C show that phosphorus also decreases the nitrogen diffusivity in iron. In previous work on the Fe-P-N system, phosphorus was found to reduce the nitrogen solubility in liquid iron slightly.&apos; Indirect evidence for similar behavior in a Fe at low temperature was obtained by Dickenscheid and Brauner.&apos; These authors found that phosphorus reduces the height of the internal-friction peak due to dissolved nitrogen. The results of Dickenscheid and Brauner were confirmed by J. C. Swartz of this Laboratory in a single internal-friction experiment using the same specimen stock as in the solubility measurements described below. In the present investigation, the solubility of nitrogen in a fer rite-stabilized Fe-1.0 wt pct P alloy was measured in the temperature range from 800" to 1300°C. Additional experiments were performed in the temperature range from 440° to 585°C, using an Fe-0.23 wt pct P alloy and NH3-H2 gas mixtures. EXPERIMENTAL The experiments were performed in a vertical tube furnace wound with platinum wire. For experimental temperatures of 800°C and above, a mixture of 5 pct Hz in N2 was used as the reacting gas. The gas mixture was prepurified from oxygen by passage over platinized asbestos at 450°C, and subsequently over anhydrone to remove water. Flow rates of the gases were measured with capillary flow meters. The temperature was measured before and after each experiment with a Pt/Pt-10 pct Rh thermocouple. The specimens used for the high-temperature solubility measurements were in the form of rectangular plates, 0.534 by 1.6 by 3.8 cm. The specimens were cleaned in trichloroethylene and annealed for 2 hr in hydrogen at the beginning of each experiment. In measuring the nitrogen solubility, the specimens were held in the reacting gas until equilibrated, then cooled in a water-cooled copper block at the bottom of the furnace. The time needed for equilibration at 1150°C was determined by measuring the average nitrogen content of the 1.0 pct P alloy as a function of reaction time. As will be described, the nitrogen diffusivity in the alloy at 1150°C is only slightly less than its calculated diffusivity in pure iron. At temperatures other than 1150°C, the reaction time used in measuring the nitrogen solubility was about twice the calculated equilibration time for pure iron at the same temperature. With a few exceptions, the procedure for the low-temperature solubility measurements was the same as that described above. The compositions of the NH3-H2 gas mixtures were determined by collecting gas samples from the gas train and analyzing them for NH3 by titration with HC1. The specimen thicknesses were less than those used for the high-temperature experiments, eg., 0.124 and 0.051 cm for measurements at 585° and 440°C, respectively. Nitrogen concentrations were obtained by chemical analysis, using the Kjeldahl method. The Fe-P alloys were made by adding ferrophos-phorus to electrolytic Plastiron (Type 104 A). Commercial ferrophosphorus, containing 3 pct Mn and 0.35 pct Si as the major impurities, was first purified by melting under an FeO slag. In a separate heat, the electrolytic iron was melted and vacuum-carbon-deoxidized prior to making the ferrophosphorus addition. The principal impurities and their concentrations in weight percent in the 1.0 pct P alloy are as follows: Mn, 0.01; Si, <0.01; C, 0.01; 0, 0.003; and N, 0.0012. The impurity levels in the 0.23 pct P alloy are con-

Jan 1, 1968

By G. Purcell, S. C. Sun

In an attempt to determine the relative collecting ability of 18-carbon fatty acids, studies were performed on rutile in aqueous solutions of the fatty acid soaps. The preceding article reported the electro-kinetic properties; this article outlines the flotation behavior. Results of these flotation experiments are described and correlated with the electrokinetic results. Recent studies of the electrokinetic1-4 and the electrochemical5,6 properties of a few solid-liquid interfaces have provided a better understanding of the flotation process. A number of investigators have attempted to determine the relative collecting ability of 18-carbon fatty acids, but their published results (even for the same mineral) vary widely. Such lack of agreement indicated a need for further investigation. In an effort, therefore, to resolve the problem, electro-kinetic studies were made on rutile in aqueous solutions of the fatty acid soaps. Following the determination of the electrokinetic properties, the flotation behavior of rutile was studied. Results of these flotation experiments are described in this paper and are correlated with the electrokinetic results. MATERIALS AND EXPERIMENTAL PROCEDURE Materials: Pure -28, + 35-mesh rutile crystals were used for all flotation tests, and nitrogen-saturated conductivity water was used throughout. Sodium hydroxide and hydrochloric acid were added for pH regulation. The methods of purification for these materials and the preparation of the soaps have been described elsewhere. 7 Equipment: A Hallimond cell, constructed in a manner similar to that described by Fuerstenau, Metzger and Seele,8 was used for the flotation of mineral particles; however, a coarse pyrex frit was substituted for the capillary. Procedure: Purified nitrogen was led through a two- way stopcock into a graduated cylinder partly filled with water. The gas forced water from the cylinder back into a header tank until the water level in the cylinder coincided with a predetermined mark. Reversal of the stopcock then allowed water in the tank to force nitrogen into the cell until the water in the graduated cylinder rose to a second predetermined mark. In this way a constant volume of nitrogen under practically constant pressure was used for each flotation test. However, the flotation time varied, depending upon the amount of mineral floated and the pH of the solution. Rutile crystals were transferred under water from a storage bottle by a glass scoop holding 1.7 g. Consistency of the scoop samples was good, varying from a low value of 1.67 to a high of 1.74 g. The water added to the conditioning bottle during mineral transfer was drained off, and then 2 cu cm of either hydrochloric acid or sodium hydroxide were added. The concentration of pH regulator was adjusted to give approximately the final soap solution pH that was required. The order of addition of reagents did not affect the results within the limits of experimental error. Soap solution of the required concentration was added under nitrogen pressure to fill the bottles completely. Conditioning for 1 hr was carried out on rolls rotating at 35 rpm. After conditioning, 2.5 cu cm of solution were run off into the container of a Beckman (model G) glass electrode pH meter. The electrodes were rinsed in this solution, which was then discarded, and 2.5 cu cm more were added for pH determination. The remaining solution and the mineral were transferred to the cell; care was taken to ensure that all mineral was washed out of the bottle by the conditioning solution. With the cell back in its flotation position the liquid just reached the desired level, and the test was started immediately. The amount of agitation in the cell was kept constant, and flotation was carried out without the use of a frother. In each series of ten tests one was run with no collector added to ensure that the mineral had not become contaminated, and two were conditioned at the same pH to check reproducibility. After each test the cell was dismounted, soaked in cleaning solution, washed in hot water and then rinsed with distilled water.

Jan 1, 1963

By B. C. Raynes

IN the early part of 1952, under the auspices of the U. S. Atomic Energy Commission, Horizons Inc. undertook an investigation dealing with the preparation of high purity thorium metal in order to develop an economically competitive production process for this metal based on a recovery of the metal by a fused salt electrolysis, since a survey of the literature of thorium chemistry indicated that electrolytic methods had not received much attention, despite the consideration that electrochemical production methods often offer attractive commercial potentialities. Thorium metal has been prepared by methods which fall into four general categories: 1) reduction of halides or double halides; 2) reduction of the oxide; 3) thermal decomposition of halides; and 4) electrolytic methods. Some of the important results obtained by various investigators since about 1900 in recorded attempts to prepare pure thorium metal are summarized in Table I. A bibliography of pertinent literature is included in this paper. Thorium is strongly electropositive and possesses a great affinity for oxygen and nitrogen. As a result the prospects for the production of high purity thorium from aqueous media or oxygen bearing compounds are remote. The most promising and profitable area of investigation for production of thorium metal lies in fused salt electrolysis. Thorium has been produced previously by this technique from halide salts in fused alkali chloride eutectic mixtures. Until recently, however, the lack of known large uses for thorium has inhibited the investigation of these methods. The basic problem in an investigation into fused salt production methods for thorium is to develop a suitable fused salt system for the economic preparation of thorium. The first portion of the work in these laboratories was a small scale investigation of the electrolysis of potassium thorium fluoride, KThF5, under a variety of conditions. High purity thorium was prepared in this manner, but the process did not appear to offer the simplest and most attractive continuous commercial operation. The work reported here relates to an all-chloride system employing thorium chloride as the cell feed. ThCL4 was produced as an anhydrous material stabilized in molten sodium chloride. This product, further diluted in NaCl, was subjected to electrolysis. The electrolytic process has been studied in cells capable of holding up to 50 lb total salt charge. Ductile, pure thorium metal has been reproducibly obtained in this operation. Considerable experimentation was carried out in the preparation of ThCL as a cell feed free from moisture, oxides, and other impurities. Thorium was cathodically deposited as a coarsely crystalline powder interspersed with residual bath salts. Aqueous procedures for separating and recovering the metal were developed. The thorium metal powder obtained has been evaluated with respect to its hardness, chemical purity, and certain other physical properties. Preparation of ThC1,—Thorium chloride, and the chlorides of some other metals (aluminum, beryllium, tantalum, zirconium, etc.) cannot be obtained from aqueous solution by direct heating and evaporation. Evaporation and heating of a solution of thorium chloride yields a hydrated salt or partially hydrated salt, and finally Tho,. Anhydrous thorium chloride is obtained by forming a hydrated ammonium chloride complex salt in acidified water solution, dehydrating this compound, and finally decomposing the double salt and subliming the ammonium chloride component. Various methods for the preparation of anhydrous thorium chloride, in accordance with this concept, were investigated as indicated in Table I1 from hydrated thorium chloride (ThCl, . 3H2O), and from thorium oxycarbonate (ThOCO,). In the method found most satisfactory for this work, thorium oxycarbonate was dissolved in an excess of concentrated HC1 to give a clear yellow solution. At least 2 mol NH,Cl were added to the solution per mol of contained thorium. Ammonium thorium chloride hydrate was crystallized from solution by cooling and saturation with HC1. The resultant complex, (NH,Cl),ThCl;xH,O, was dehydrated by evaporation at 130° to 150°C and thoroughly dried at about 250°C. The dried ammanium thorium chloride was then mixed with sodium chloride in proportions to form NaThCL or to produce a ThCL4-NaCl mixture with a given thorium content. The ammonium chloride was sublimed off at temperatures above 500°C in an inert atmosphere furnace to give an anhydrous chloride source electrolyte, essentially free of Tho, and of NKC1.

Jan 1, 1958

By Donald B. Evans, Robert D. Pehlke

The solubility of nilrogen in liquid binary alloys of iron with Litanium. zivconium, columbium, vanndiurn, and tantalum was measured for alloy composiLions up to the solalbility limils of lhe alloy nitrides. All five alloying agents were found to decrease markedly the activity coefficient of nitrogen in liquid ivon. The metal/nitvogen mole ralios in the alloy nitrides formed were generally .found to be slighlly greater than 1.0, but in no case greater than 1.5. From the experimental data, the standard free energies of fortmation of titanium and zir-conium nitrides have been calculated for the Lemperaluve range 1550° to 1750 C. The solublily Products for columbium, tantalum, and vanadium nitrides are also reported. A number of research investigations have examined the effect of refractory metals on the solubility of nitrogen in liquid iron. Although data on zirconium are not available, investigators are in agreement that titanium, vanadium, columbium, and tantalum markedly increase the solubility of nitrogen in liquid iron. This fact alone makes desirable the acquisition of thermodynamic data for these elements in liquid iron. Since refractory metals are known to be stable nitride formers, they have been suggested as steel denitrifying agents, and some of their nitrides have recently been considered as containment materials for liquid iron and iron alloys. Most available thermodynamic data for these metals relate to their dilute concentrations, but effective thermodynamic treatment of these applications requires data at concentrations near the solubility limit of the alloy nitride. Although some work has been done at relatively high alloy concentrations in liquid iron (particularly for vanadium 2,3 and titanium 2,4), the results have been somewhat contradictory. Disagreement may be partly attributed to the fact that the compositions of most refractory metal nitrides have been shown to be nonstoichiometric, and to vary 2,5-8 depending on the temperature and nitrogen gas pressure with which the solid nitride phase is in equilibrium. One purpose of this study consequently has been to determine the compositions of the refractory metal nitrides precipitated from a liquid iron solution. EXPERIMENTAL PROCEDURE Rao and Parlee2 and Evans and Pehlke 9 have discussed the technique for measuring the solubility product of an alloy nitride phase in liquid iron by finding the point of departure of the nitrogen solubility from Sieverts&apos; law. The method consists of measuring the solubility of nitrogen in a melt of iron containing a known concentration of a second metal as a function of the nitrogen gas pressure over the melt. In this study the second metal was one of the refractory metals titanium, zirconium, columbium, vanadium, or tantalum. When the nitrogen pressure at which the refractory nitride forms is reached, a deviation of the measured solubility of nitrogen in the melt from Sieverts&apos; law is observed in the form of a "pressure halt." The concentration of nitrogen in the melt associated with this breakpoint in the nitrogen-absorption curve is then used to calculate the nitride solubility. The Sieverts method was used to measure nitrogen solubility as a function of nitrogen pressure and temperature. The experimental equipment for this technique has been previously described in detail. 1,9 Charge materials used were vacuum-melted high-purity iron (Ferrovac-E) and the best commercial grades of the refractory metals obtainable (in all cases at least 99.8+ pct pure). Recrystallized alumina crucibles were used to hold all melts except those containing zirconium, for which zirconia crucibles were necessary. Temperatures were measured by a disappearing-filament type optical pyrometer sighted vertically downward on the melt surface through a 1/4-in.-diameter sight hole in the crucible lid. By means of a technique previously described, 9 in which the refractory-metal nitride was precipitated at one temperature then redis-solved by raising the temperature 50°C and precipitated again at a higher temperature, it was possible to obtain data over a temperature range of up to 200°C on a single melt. It was found that this technique could not be used with melts containing zir-

Jan 1, 1965

By I. B. Cadoff, J. C. Bilello, R. Rosenberg

Diffiusion of magnesium into the surface of LiF crystals to controlled depths and subsequent heat treatments provided a wide range of surface zone harahesses and structure, The bend strength of the LiF crystals was increased by as much as an or-dev of magnitude. Ductility was achieved when dislocation generation occurred in the diffusion zone or when dislocations penetrated to the surface from the intevior. A critical surface hardness of 130 to 140 kg per sq mm was found helozu which generation could take place in the diffusion zone and ahoue which the zone was impenetrable, This hardness was obtainable by several methods, among them the aging of quenched MgF2 -LiF solutions to produce MgF, precipitation. Maximum hardness was ohtained in quenched specimens with no visihle evidence of MgF,. Diffusion-zone formation followed a parabolic rate law and an activation energy of 20.9 kcal per mole was obtained for the process. RECENTLY, the properties of ionic crystals as related to surface condition have been receiving much attention, specifically the transitions between ductile and brittle behavior. Originally Joffe 1 showed that NaCl crystals could be made ductile by immersion in water and related this to the elimination of surface microcracks. Aerts and DeKeyser 2 and Gorur 3&apos; have subsequently shown that ionic crystals are inherently ductile and are embrittled through contact with air. Machlin and Murray4 hypothesized that a layer of NaCIO3 produced by contact of ozone with NaCl induced embrittlement by acting as a barrier to outward dislocation flow. westwood,&apos; Rosenberg and Cadoff,9 and Bilello and cadoff&apos; have reported surface strengthening of LiF crystals by coating with a magnesium compound and then heat treating for adherence. The major effect of the coat was to inhibit dislocation-slip lines from reaching the specimen surface. westwoods showed microcrack formation and fracture to be caused by slip-band interactions at the surface. The material presented in this paper is an extension of the work reported earlier by Bilello, Rosenberg, and cadoff&apos;6,7 and illustrates the wide range of surface properties and bulk behavior obtainable by use of heat-treated magnesium-diffused surface regions in LiF crystals. EXPERIMENTAL PROCEDURE The LiF single crystals were obtained from the Harshaw Chemical Co. Some batch to batch variation was observed; therefore all specimens for a given test series were cleaved from the same crystal. The typical dimension used was 1 by 0.1 by 0.40 in. Surface damage resulting from cleavage was removed by chemically polishing in a 2 pct NH4OH solution. Each group of specimens was given a vacuum anneal at 700°C for 4 hr to provide a base standard for measuring comparative effects of various surface treatments. To produce the reacted surface zone, the annealed specimens were immersed in a boiling suspension of MgF, in doubly distilled HzO, agitated slbwly for 30 sec, removed, and dried at room temperature. Uniform coatings of MgF, were deposited with a thickness of approximately 5 mils. It should be noted that this technique can be modified for use with crystals which are soluble in water by using boiling absolute alcohol as the dissolving medium. This was found effective for the coating of NaCl with MgF2. The diffused surface zone was obtained by annealing the coated samples at elevated temperatures in a vacuum of lob4 mm Hg. Penetration depth was controlled by varying the annealing time from 1/2 to 28 hr. After heat treatment, the samples were tested for bend strength and hardness. Load was applied by four-point bending in a hard-beam testing jig. Four-point rather than three-point bending was used to provide a wide area of constant stress and to minimize the effect of localized inhomogenities in the specimen. The deflection rate was 8 x min-&apos; and the distance between knife edges was 1/4 in. Load-time curves were obtained from a chart recorder coupled to the machine and converted to resolved shear stress on the shear plane vs deflection, as plotted in the figures. The unstressed portions of the sample outside of the two outer knife edges were used for the microhardness studies. Microhardness measurements were made with a Bergsman tester attached to a Reichert metallograph. All hardness impres-

Jan 1, 1964

By R. J. Lutton

Empirical data from 91 rock excavations have been used to construct a family of slope curves on a chart relating excavation height and inclination. The highest and steepest slopes from each excavation are plotted and connected by a line. The 31 1ines appear to establish one or two geometrical slope fields through which the curves are projected. The curves apparently represent a lumped eflect of many factors too complex to be considered individually. Important factors such as geological structure or ground-water conditions can dominate the picture, but where these factors do not overshadow others, the slope chart should be useful for estimating or checking optimum inclination. The U.S. Army Corps of Engineers (USAE) has been engaged since 1962 with the U.S. Atomic Energy Commission in a joint research program to develop nuclear excavation technology. The Corps is responsible for collecting the requisite data on engineering and construction problems associated with nuclear excavation. The ultimate objective is to develop a capability to use nuclear explosives as a construction tool on public works projects such as harbors and canals. The present study on empirical inclination-height curves for conventionally excavated slopes is an outgrowth of an investigation&apos; sponsored by the USAE Nuclear Cratering Group on applicability of data from existing excavations in establishing guides for engineering judgment in crater excavation. Data were generously contributed by over 50 mining companies among other organizations. Inasmuch as several companies preferred that their contribution be anonymous, all data are treated so here. Some Factors Affecting Stability Many factors affect or are suspected of affecting the stability of excavated slopes, e.g., adverse structural orientation, degree of structural ordering, ground water, climatic conditions, mechanics of excavation, and plan-profile configuration. Such factors are lumped together in developing a slope chart. Obviously geological structure and ground water can overshadow all other factors. Where such is the case, the simplification of slope charts may give an erroneous picture (not conservative enough). A further complication results from the fact that the concept of stability may vary according to the use of the excavations. For example, slope adjustments that would be regarded as failure in a powerhouse excavation, might be tolerable in a mining operation. Mine slopes are continually being modified by further excavation, and instability that would develop in a similar permanent excavation slope over a period of years might not have time to develop in a mine. Inclination vs. Height Charts Charts of inclination vs. height for particular formations or conditions have been used in the past as an aid for designing excavation slopes. Some of these have been based upon empirical analyses of collections of data and experience. MacDonald" and Lane have presented slope tables and charts for excavated and natural slopes in relatively weak sandstone and shale. Coates&apos; has shown an inclination-height chart for slopes in incompetent rock. Most organizations have developed slope design criteria which relate bench widths, heights, and inclinations to use in various rocks. Slope data collected in present studies can be similarly used to develop inclination-height charts; however, a plot of all slopes on such a chart shows very little because of the wide spread of the data. Reasons for the dispersion of points are: (1) many slopes are not carried at optimum inclination, particularly in mines where maintaining roadways and following irregularities of ore bodies are more important than achieving steep inclinations; (2) many engineers and geologists with varied backgrounds and viewpoints have been involved in designing these slopes; and (3) each slope is characterized by a unique combination of factors affecting stability and in turn optimum inclination. Significant curves can sometimes be constructed where the points can be grouped into related clusters from the same excavation. The essence of this approach appears when only two slopes from each excavation are considered—the highest slope and the steepest slope, connected by a line segment (Fig. 1). This reduces considerably the usable data because in many cases only one of these two slopes is available. Nevertheless, the concession seems justified. Construction of Slope Curves Ninety-one pairs of points and connecting line segments were assembled in this study. The line segments were assumed to approximate a geometrical slope field (Fig. 2), and a family of curves has been visually projected through to represent the slope field. It should be

Jan 1, 1971