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By M. C. Lavine, H. C. Gatos, R. S. Mroczkowski

The structure of GaAs-Ge heterojunctions prepared by a back-melting process was studied by X-rav diffraction, melallographic, and electron-micro-analyzer techniques. The boundary region between the GaAs and the germanium was found to consist of a four-layered band. A discontinuity between the two inner bands was brought about by solidification occurring simultaneously from the GaAs and the germanium side. The junction material OH either side of the central discotinuity was found to have grown as a single Crystal with the orientation of the parent substrate. It was found essential to determine the GaAs-Ge phase diagram. This was accomplished by a series of alloys containing 0 to 40 wt pet GaAs. Over this range the diagram is a simple eutectic with the eutectic point at 74 wt pet Ge and 845 C. The limiting- solubility of Coils in germanium was found to bc less than 5 wt pet. The Kossel divergent-beam X-ray technique was used to study orientation relationships across the boundary lager. A great deal of effort has been recently expended on the electrical properties of heterojunctions. Little attention, however, has been given to the metallurgical variables which may be of importance in the formation of the junctions. The present work was undertaken to investigate some of the more pertinent metallurgical aspects of interface-alloyed GaAs-Ge heterojunctions. Such parameters as solidification processes, composition gradients, orientation effects, and the accommodation of crystal structures have been the objects of study in this program. EXPERIMENTAL PROCEDURES Phase Diagram. The phase diagram of the GaAs-Ge pseudobinary system was determined by means of cooling curves. A Bridgeman furnace was employed with the center section maintained at 1200°C and the upper section at 800°C. Melts varying from 0 to 40 at. pct in GaAs content were used. Each charge was incapsulated under a two-thirds atmosphere of argon in a carbon-coated quartz tube. Five min in the furnace hot zone provided rapid melting and homogenization. The capsule was then removed to the cooler portion of the furnace. Cooling times were of the order of 3 min. The resulting homogeneous microstructure indicated that equilibrium conditions were obtained by this procedure. Formation of Heterojunctions. Rectangular parallelepiped single-crystal samples were cut with the large faces of either the (l00), (110), or (111) orientation. The remaining four surfaces were also cut to specific orientations to permit accurate relative orientation of the GaAs-Ge pairs. The

Jan 1, 1965

By P. B. Knuckey, D. Littleford

The Kalengwa mine, situated in a remote area of Zambia in Central Africa, has presented some unique problems to the planners engaged in developing the deposit. This small, high grade copper deposit contains some 1,688,000 tons of ore at a grade of 9.3% contained copper. Of this 362,000 tons is classified as high grade ore at 27.2% Cu, the coarse fraction of which can be fed directly to converters; 733,000 is classed as intermediate grade ore averaging 6.3% Cu, and 593,000 tons classed as low grade ore containing 2.1% Cu. The geology of the deposit and the establishment of the mining operation is fully described. A concentrator is being built at Kalengwa to treat the high grade fine product, intermediate, and low grade ore, whilst the coarse high grade ore will be trucked to the Copperbelt smelters for direct smelting. Details of metallurgical processing are given. The decision to truck the coarse high grade ore to the smelters on the Copperbelt necessitated the construction of a new 200-mile road, the setting up of a fleet of heavy ore transport trucks and associated equipment. The remoteness of the area from established communication facilities on the Copperbelt necessitated the provision of radio communications between Kalengwa and the head office at Kalulushi, and the establishment of a regular mine air service. The paper also describes the training of an unsophisticated local population in the operation of heavy plant and machinery, the establishment of the township, and the provision of health services.

Jan 1, 1972

By R. W. Gurry

WHEN a steel in the austenitic state, with all its carbon in solution, is maintained, at constant temperature, in contact with a gas that removes the carbon from the surface, vet without otherwise altering the composition of the steel, the change in weight of the specimen, after any period of exposure, is a direct measure of the amount of carbon it has then lost. The purpose of the present paper is to show how, by application of established mathematical reasoning based on the fundamental diffusion law and on certain postulates, this loss of weight yields a complete picture of the distribution of carbon throughout a specimen of regular shape after any period of exposure, with all the accuracy required in any practical occurrence of decarburization. Precisely the same is true for the gain in weight during the reverse process of carburization, or for the gradual gain or loss of any element, so long as the steel comprises only a single phase at temperature, provided always that the experimental conditions conform to the postulates. The change in carbon content from surface to center of the specimen is always continuous, when everything is in solution, even though under the microscope the decarburized zone (or carburized rim) may appear to be sharply defined. The experimental procedure is described and some typical results are presented, which are then interpreted by application of the diffusion law. EXPERIMENTAL PROCEDURE Initially an endeavor was made to follow the gain of weight during the process of carburization in a hydrogen-toluene atmosphere, but it was soon found that the specimen became coated with graphite, which could not be removed without some loss of metal; therefore it was decided to continue carburization until the steel was saturated throughout, to remove all graphite from the surface of the specimen, and then to follow the loss of weight during decarburization in a moist hydrogen atmosphere at the same temperature as that used for carburizing. The carburizing procedure has been described in an earlier paper;1 it suffices to state here that the carburization lasted about 140 hr. at 760°C. (1760°F.) and 44 hr. at 1110°C. (2030°F.), these periods being long enough-on the basis of the calculations presented later-to ensure that the specimen was about 9.99 per cent saturated at each temperature. The speci¬men was a cylinder about 3.8 cm. long and 0.475 cm. in diameter; the materials were carbonyl iron, a commercial low-metalloid iron, and a steel with 3.6 per cent nickel and the usual proportion of other elements. The fully [carburized] specimen, after cooling at the top of the furnace tube, was placed in a lathe and sandpapered to remove all graphite; then the diameter was measured with a micrometer caliper, and the initial weighing (corresponding to complete saturation) was made. By means of a

Jan 1, 1942

INTRODUCTION Data available on prophyry copper occurrences in the Andean, Caribbean, Appalachian, and Cordilleran orogens may be categorized in a manner to suggest a hypothetical evolution for deposits that occur in the western hemisphere. A classification of de- posits is also suggested. A classification dependent on internal structure of a porphyry copper deposit would lead to two broad categories, breccia pipe and stockwork models. A classification of this type is examined herein but it is not universally accepted in the literature. Modeling based on igneous petrography as well as metasomatism attendant with the sulfide mineralization is more widely accepted by economic geologists whose evaluation of porphyry systems is influenced by the presence or absence of a phyllic zone. Lowell and Guilbert model deposits ordinarily include a phyllic zone, whereas those of the diorite model do not. Position of the phyllic zone in the alteration sequence is a significant ore guide. Should the phyllic zone be absent, dependence on alteration zoning to identify metallization is weakened. Presence or absence of the phyllic zone therefore is a significant parameter in the economic evaluation of a porphyry copper deposit (Hollister. et al., 1975). The Lowell and Guilbert (1970) model commonly includes a phyllic zone in quartz- bearing rocks. Parameters of both calc-alkalic and the quartz monzonite models mentioned elsewhere in this volume are sufficiently close to the Lowell and Guilbert (1970) model that it should be expanded to encompass them. The diorite model remains separate and distinct because deposits of this type are characterized by an absence of quartz in the pluton, commonly highly gold: copper ratios, low molybdenum content, and regular absence of sericite in the alteration zones. Therefore, for the benefit of those

Jan 1, 1978

A-Metal Mining B-Minerals Beneficiation F-Coal H-Industrial Minerals

Jan 11, 1950

By J. E. Johnson

The general construction of blast-furnaces has undergone no radical change in more than a generation. When the old style of masonry construction was replaced by the steel shell, the masonry piers were simultaneously replaced by columns, never lese than 6 and frequently 12 or 16 in number, set under the mantle-ring. These columns were at first unvaryingly made of cast-iron, but in more recent years have frequently been made of structural steel. The furnace itself has recently been the subject of radical changes; in some cases the thin-lined construction has been adopted for the whole furnace, and in other cases it has been adopted for a zone immediately above the bosh, raising the mantle several feet to make this possible, but still the style of construction with columns set immediately under the mantle has been universally followed. In spite of the apparent fixity of this type of construction it is open to grave disadvantages from the operating point of view, which may be briefly outlined as follows: The slope of the bosh and size of the crucible are such as to leave scant room inside the columns for the necessary water-piping, etc. The bustle-pipe must necessarily be outside the columns and the penstocks have to pass between them, with the result that the columns are frequently much in the way when changing the tuyeres or otherwise handling the penstocks. Moreover, the hearth-jacket requires a diameter but little smaller than the circle of the inside of the columns, and as a result the cooling-water ditch for protection against breakouts is exceedingly limited in width. As a consequence of these conditions, when any work requires to be done around the furnace, such as changing a tuyere or working on the cooling-water pipes, the amount of room left between the columns, pen-

Jan 1, 1913

By M. H. Waxman, M. Gondouin, H. J. Hill

Streaming-potential experiments were conducted within the Muddy- and Dakota-sandstone interval of a Denver basin well. Analysis of the data shows that, for this case, streaming potentials opposite sands were higher than those opposite shales when the mud was fresh. Streaming potentials opposite shales, however, were of sufficient magniiIlde to be important in SP interpretation. They were linearly dependent upon pressure differential, and they increased with mud filtrate resistivity. The magnitude of streaming potentials opposite sands was influenced by the characteristics of the original mud cake formed at the time of drilling. Use of mud samples taken at the time of logging may not always be satisfactory for determining streaming-potential corrections. Both the streaming and electrochemical potentials were found to be affected by the previous history of the borehole system. Following a change in mud characteristics, several days were required for SP stabilization. This was, in part, due to the mud cake acting as an imperfect shale membrane. INTRODUCTION Laboratory investigations by Wyllie,1 Salisch,2 Moore," Sen Gupta and Bannerjee,0 and Hill and Anderson' have shown that streaming potentials developed across mud cakes deposited on permeable filter beds are of sufficient magnitude to be critically important in SP interpretation. Streaming potentials across shales have been reported by Schenck,' Gondouin and Scala; and Hill and Anderson." The magnitude of the shale streaming potentials obtained by Schenck and by Gondouin et a1 led these authors to conclude that in many cases the shale streaming potential would approximately equal the mud-cake streaming potential. Hill and Anderson, however, obtained somewhat lower magnitudes of shale streaming potential. The field experiment described in the present paper was a cooperative project carried out by the respective operations and research departments of Schlumberger Well Surveying Corp., Shell Development Co. and Shell Oil Co. The primary objective of the experiment was to determine in the borehole the streaming-potential behavior of both shales and mud cakes under conditions approaching, as nearly as possible, those normally encountered in logging practice. METHODS AND EQUIPMENT WELL A Muddy- and Dakota-sandstone vie11 in the Denver basin was chosen for the experiment. Both sandstones were water-bearing and, since reservoir pressures in these sandstones are abnormally low (gradient of approximately 0.25 psi/ft), it was expected that studies of streaming potential could be conducted from low-pressure differentials (approximately 200 psi) to about 27000 psi by bailing mud from the hole, filling up and then applying wellhead pressure. The selected well encountered the Muddy sand-

By Carl F. Floe, John Chipman

The system molten copper-oxygen-sulphur is of interest from both the practical and theoretical standpoints; practically, because oxygen and sulphur play an important role in the commercial production of copper, and theoretically because it offers a chance to study the reaction between an oxide gas, SO2, and a molten metal. Reactions of this type, such as that between CO or CO2 and molten iron, are important in many metallurgical operations. Again, the determination of any gas-metal equilibrium is of theoretical interest and value insofar as it contributes to the general development of the laws for solution of gases in metals. This problem is being given an increasing amount of attention in modern metallurgy. This paper is the first of a series and presents the results of a determination of the solubility of sulphur dioxide in molten copper at temperatures from 1100" to 1500ºC., and pressures from about 20 mm. of mercury to somewhat above atmospheric. Review of Previous Work The solubility of gases in most liquids has been found to obey Henry's law, which states that for a fixed temperature the amount of gas dissolved is directly proportional to the pressure. However this law does not hold for liquid metals. Instead, it appears that for many gases, particularly the simple diatomic ones such as O2, N2 and H2, the amount dissolved in liquid metals is directly proportional to the square root of the pressure. This is known as Sieverts' law. It may be recognized as a special case of Henry's law, which applies when the solute gas is dissociated into atoms or when it reacts with the solvent metal to form solute molecules containing single atoms of the gaseous elements, as, for example: 2M+G2=2MG K=(MG)2 /M2 X PG2 [I] which, if the solubility is not too high and the concentration of metal therefore nearly constant, can be simplified to: MG = K1 vPG2 [2 Following the same reasoning, it would be expected that the solubility of SO2 in copper would be proportional to the cube root of the pressure, the reaction being as follows: 6Cu + SO2 = Cu2S + 2Cu2O [3] K= Cu2S X (Cu2O)2 i - (Cu)6(Pso2) [4] or, neglecting the change in metal concentration and considering that the concentrations of sulphur and oxygen are both proportional to the volume V of gas absorbed: K1 =V3SO2 /Pso2 or

Jan 1, 1941

By R. M. Douthwaite, G. Birkbeck

The effect of grain size and specimen dimensions on the occurrence and magnitude of a yield point drop in pure iron has been examined. The tests were done at room temperature. The results indicate that gain size is the critical factor determining whether a yield drop occurs. The specimen diameter:gain size ratio does not influence the magnitude of the yield drop for the range of gain size and specimen diameters investigated. HUTCHINSON,' petchY2 and worthington3 have investigated the grain size dependence of the upper yield stress (uUYP) and the yield point drop, ouyp - aLYP, in Armco iron, mild steel, and Si-Fe, respectively. These authors used center-annealed wires to avoid stress concentration from specimen shoulders and to ensure uniformity of the applied stress. Coarsegrained specimens show no yield point drop; the yield point drop then increases as d-'I2 increases (where d is the grain diameter). These results can be understood in terms of Petch's analysis2 in which the magnitude of amp depends on the strain rate in the (limited) number of grains deforming plastically at the upper yield point. If N grains per unit volume are undergoing plastic deformation, the strain rate in the deforming grains is l/Nd3 times higher at the upper yield stress than when the whole specimen deforms homogeneously. If N is constant and independent of grain size at uUyp, then all the grains are deforming when ~d~ = 1, so there is no yield point drop. At finer grain sizes, the yield point drop is given by: where AU, is the friction stress increase corresponding to a tenfold strain rate increase. Christ, Smith, and Burton studied the upper yield point in 0.050-in.-diam wire specimens prepared from zone-refined iron. Each end of the 2; -in. specimens was soldered to a & -in. diam steel ball and the load applied through the two balls. There was a yield point drop in specimens with grain diameters less than 0.1 mm; no drop was observed in specimens of grain diameter greater than 0.1 mm that were free from veining substructure, but specimens of grain diameter 0.129 mm, annealed in the y range, showed an upper yield point. and this was associated with the presence of a veining substructure in these specimens. Christ et al. suggested the upper yield point occurs when more than a specific number of grains fill the specimen cross section so a multiplicity of slip is required to initiate plastic deformation. Table I summarizes the published data on the grain size at which the yield drop disappears. On the basis of this data the ratio of specimen diameter:grain diameter = 5 to 27 appears to be the critical value for the occurrence of a yield point drop. Thus, petch2 interprets the appearance and magnitude of the yield point drop in terms of the limited number of grains deforming plastically at uuyp, whereas Christ et a1. consider that the occurrence of the yield drop depends on the ratio specimen diame-ter:grain diameter. The published data cover a wide variety of materials so some variation between the results is to be expected, but the size range covered in the data of Table I is rather limited. In an attempt to discover whether the specimen diameter:grain size ratio or the grain diameter is critical in determining

Jan 1, 1969

By Leonard Austin

WHAT Colonel Dwight says regarding the treat-ment of oxidized ores1 holds true also of the silver-lead smelting operations in Utah. The ore sought for was such as would, with appropriate fluxes, yield slag, and "lead bullion," as the lead reduced from the ore and carrying its gold and silver, was called. No matte, and probably little or no speiss, was yielded, and hence there was nothing to roast, either of ore or matte. But, by 1880, when I first took hold in smelting, there was quite a production of matte at the works of the Ger-mania Smelting and Refining Co., Utah, because, by that time, ores containing some pyrite and galena were being smelted. This was due, as at the Grant Works, Denver, to the more attractive price paid for the treatment of such ores. The matte, containing about 5 per cent. copper, was accordingly heap-roasted and returned to the blast furnace for the recovery of its contained metals. By this time there had been built a long-bedded, hand-rabbled reverber-atory roaster with a hearth of about 40 by 10 ft. in size, and in this matte and ore, crushed at the sampling mill, was treated. When, in 1892, I took control of this works, called& now the Germania Lead Works, three other roasters had been added, but the prac-tice of heap-roasting continued. This had the merit of needing no equipment, and of doing good work, because the pieces that were imperfectly roasted went back upon the next roast heap. At this time, when some suitable lump ore was obtainable, I roasted in heaps, in a satisfactory way. By 1892, the Bruckner cylinder roaster had been installed, which, compared with the reverberatory roaster, reduced labor. As such a cylinder revolves, a talus of ore is formed within it and at the same time fresh surfaces are exposed to the air, but the trouble was that the air did not reach to the bottom of the cylinder. This we corrected by placing a steam jet at the fire-box end, to project the air down-ward upon this stagnant ore, thus increasing the speed and completeness of roasting without at the same time increasing dust formation. The firing, if skilfully done, gave a somewhat sintered product, but with certain ores a slight access of heat over the normal would cause accretions to form within the cylinder near the fire end. These could be cut off by running back the fire box and barring off the crusts. It was in 1895 that the Bruckner cylinders at the Arkansas Valley plant, Leadville, were giving unsatis-factory service and I was called in to investigate. The steam jet was put in use as at the Germania Lead Works, but we found that, due to the altitude (10,500 ft.), combustion was feebler than at sea level or even at 4000 to 5000 ft. Later it appears, as Colonel Dwight states, that R. D. Rhodes and Mots sought to increase the air supply by admission through perforated tiles, but the trouble was due to the air itself.

Jan 8, 1922

By Carl F. Floe, John Chipman

A year ago the authors published a paper on the solubility of sulphur dioxide in molten copper.l The data in that paper agreed closely with that obtained by previous investigators, which, however, did not agree with the theoretical predictions for solubility of triatomic gases of this type. It has generally been assumed that the reaction of solution is: 6Cu(l) + SO2(g) = Cu2S (in Cu) + 2 Cu2O (in Cu) [I] _ (CU2S)(CU2O)2 K = (Cu)6(Pso2) [2] Neglecting the slight change in copper concentration and considering that the concentrations of sulphur and oxygen are both proportional to the volume of gas absorbed, it follows that this volume should be proportional to the cube root of the pressure. It was found that a plot of the volume absorbed versus the cube root of the pressure gave a straight line, but that this line did not pass through the origin. Calculations of the equilibrium constant for the reaction showed that it was fairly constant for pressures above 100 mm. but that actually it approached zero at lower pressures. The conclusion was made therefore that the solubility as determined could not be expressed by Eq. I or by any other simple equation, particularly at low pressures. Other investigators have concluded that the solubility of sulphur dioxide in copper as well as in several copper alloys is more nearly proportional to the square root of the pressure.* Such a conclusion, however, does not satisfactorily account for the results, even when rather complicated mechanisms for the solution are assumed. The highly improbable speculations of Lepp2 and of Schneider and Esch3 based upon hypothetical dissociation pressures of Cu2O and CU2S dissolved in copper illustrate the type of reasoning that has been used to account for the discrepancy. In the discussion of the previous paper, the authors pointed out that the discrepancy might possibly be due to impurities in the copper, although the purest form available was used. Further consideration of the problem suggested that the impurities likely to have the greatest effect on the solubility of so2 in copper were oxygen, sulphur and carbon. Accordingly, further experiments have been made to show the effects of these elements. Experimental Methods The apparatus used for measuring solubility was essentially the same as that shown in the previous paper. However, since it was desired to make measurements at low pressures, a McLeod gauge was added and 6-mm. glass tubing was substituted for the capillary. This increased the "hot volume" considerably but was necessary in order to obtain good vacuums in a reasonable length of time. A mercury diffusion pump was also installed.

Jan 1, 1942

By Charles A. Ashburner

At the Philadelphia meeting of the Institute, held in February, 1881,I had the honor of reading a paper on "A New Method of Mapping the Anthracite Coal Fields of Pennsylvania."* At that time the State appropriation for the Second Geological Survey had just expired, and, as a new appropriation was not assured, no detailed plan had been adopted by Professor Lesley, State Geologist, for the practical examination of the mines, and the solution of the geological structure of special localities, or the representation in sections, vertical and columnar, of the general structure of the coal basins and coal beds. I had merely proposed a plan of mapping, as the material for the construction of maps was most available, and it was at that time uncertain what money the Survey would have to enable it to extend the surface and underground explorations, in order to make the examinations complete. After a continuation of the Survey was authorized until January, 1884, by the legislature, in May, 1881, the Anthracite Survey was regularly organized, and a plan adopted for a systematic and exhaustive geological and mine examination of the region. This plan provided for such work, other than that of mapping, as was necessary for a complete and practical geological and mining survey of a coal field. To do any geological work, of however general a character, it was absolutely. necessary that the members of the Survey Corps should obtain unrestricted access to all the mining records of the operators, which have been made with great care and accuracy and at an enormous expense during the past thirty years and more. The unanimous and generous support of the individual and corporate coal operators, of the plan of carrying on the Survey, was promptly assured, on condition that the results should be of such a character as to render them of practical utility to the property-owners and those directly interested. It was hoped

Jan 1, 1883

By J. A. Collins

THE process of plastic extension of face-centered cubic single crystal-line rods is so well understood, since the notable studies of Taylor and Elam,1 that the change in orientation of any crystal by slip and rotation may be predicted from the measured elongation. It is customary to assume a very homogeneous deformation, wherein gliding lamellae are free to rotate so that their slip direction continually approaches the axis of the rod, until a second slip system comes into operation; whereupon conjugate slip proceeds quantitatively to an end adjustment with the [112] direction in the axis of the rod. This process has been checked in many face-centered cubic materials and readily permits the preparation of specimens that have been sub-jected to various determinable amounts of shearing action. It is clearly of interest to study in such measurably strained specimens the development of a recrystallized structure on annealing and if possible detect the source of nuclei from which the new crystals grow. Strain-annealing experiments of this character have been performed by others but not in detail sufficient to permit a study, for example, of the number of recrystallized grains vs, the amount of shear. In the experiments now reported, this was done with a wide variety of orientations covering nearly the entire range of slip on a single system and corresponding to amounts of shear (ratio of shearing distance to distance between lamellae) at the conclusion of a test of from 0.08 to 0.57. A particular point was made of determining the crystallite rotation, or small angular range assumed by the octahedral slip plane after these various amounts of shear. The mechanism of recrystallization and the magnitude and effect of recovery on the recrystallization process was investigated.

Jan 1, 1940

By E. V. Potter, E. T. Hayes, H. C. Lukens

Large volumes of hydrogen are liberated at the cathode during electrolytic precipitation of manganese. Most of the gas escapes from the electrolyte, but a considerable amount may be entrapped in the manganese plate. Gas has been observed to escape from manganese melts in puffs that bite at the surface. It has been reported that castings made with electrolytic manganese tend to rise in the molds; for this reason the manganese is often treated to remove hydrogen before the melt is made or it is premelted and used as cast manganese in making the alloys. The effect of hydrogen on the properties of manganese and its alloys is not known, but its effect on iron and iron alloys has been studied extensively.l.2 The close relationship between iron and manganese suggests that hydrogen may have a similar effect on the properties of manganese and its alloys. The purpose of this investigation was to determine the amount of hydrogen or other gases in typical commercial electrolytic manganese sheet and to investigate ways of removing it most conveniently. Apparatus The apparatus used is shown schematically in Fig. I. It consists of a chamber A in which the metal sample is placed, a vacuum or pressure gauge B, volume gauge C, vacuum pump D, hydrogen container E, auxiliary gas chamber F, and furnace G. The specimen chamber was made of two concentric quartz tubes. The outer one, a, connects with the closed gas system and is surrounded by the furnace G. A second tube, b, fits closely inside a and has a small end that projects into the space for the specimen and holds the thermocouple for measuring the temperature of the sample. The inner tube is joined to the outer tube outside the furnace, with rubber tape and sealing wax, to prevent gas leakage into or out of the closed system. This type of specimen container is loaded very easily and can be used several times if molten metal does not come in contact with the quartz. An ordinary mercury manometer B is used to measure the pressure in the system. The volume gauge C is essentially another mercury manometer, but the volume of the column is much larger than normal and the height of the mercury can be varied by raising or lowering the well H. In this apparatus the tube had a volume of IOO C.C. for a 60-cm. length. For larger changes in gas volumes, auxiliary containers F were used to increase the volume of the system by known amounts. Valves were arranged so that these auxiliary containers could be filled from the system and evacuated by the pump as often as necessary to accommodate the increases in the volume of gas in the system. The furnace G, used to heat the samples, was equipped with an automatic temperature controller, which maintained the desired temperatures within ± 5°C.

Jan 1, 1945

By Hans Lundberg

IN ORDER to comprehend the help and information that may be expected from electrical prospecting, it is necessary to have at least a general knowledge of the methods and principles involved in preparing and interpreting results obtained in the field. Electrical prospecting is rather complicated, both in theory and practice, and in order to make a brief description clear to the practical mining man it has been necessary to idealize and generalize the problems, at the risk of having such simplification criticized by the theoretical man. This simplification must not be misinterpreted as showing a lack of theoretical knowledge. FIG. 1.-FLOW OF CURRENT IN AND AROUND A CONDUCTING BODY. For its operation, electrical prospecting mainly depends on-the fact that most metallic ores conduct an electric current much more readily than barren rocks. If an electric current flows through a block of ground within which a body of chalcopyrite is enclosed in country rock of schist, the current will find less resistance to its passage through the chalcopyrite than through the schist, even though the passage through the latter be much shorter. This is because the longer path through the chalcopyrite offers less resistance, owing to the superior electrical conductivity of the chalcopyrite (Fig. 1).

Jan 1, 1928

By J. McLaren Forbes

Geologists and engineers in charge of diamond drilling often have no practical experience in the work, yet they must direct the drillers. In discussing some of the problems that arise, the author of this paper has tried to remember the things he did not know about diamond drilling when he first came in contact with that work. The basic reason for most diamond-drill holes is to obtain information. The more thorough the understanding of the geological and engineering problems involved, the greater will be the benefit derived from a drilling program. One of the best methods to ensure some thinking before drilling is to record on the permanent drill log, before the hole is collared, the reasons for the work and the information desired from that particular hole. When the hole is finished, the information obtained should be recorded. Driller The choice of a diamond driller is very important. If no experienced driller is available, a competent miner who has a sense of responsibility and better than average mechanical ingenuity can do the work. The best answer to most practical drilling problems, from the standpoint of the person in charge of the drilling program, is the service of experienced diamond drillers or drilling firms. Equipment Drilling equipment should be adequate to put down the longest hole desired and handle the toughest ground encountered. The type of bit used depends upon the ground drilled. Experimenting with various bits and careful study of footage records are the best means of determining which to use. Under ordinary circumstances it is best to drill using an EX barrel when possible. The length of rod and core barrels that can be used depends on the size of the drill station. Also, the length of core barrel depends on the way the ground cores. In good ground as much core will be recovered with a 10-ft. barrel as with a shorter one, and with considerable saving of drilling time. A water pump is needed if the hole is so deep that the water pressure is not strong enough to wash out the cuttings, or if it is drilled at an angle that prevents full force of the water pressure. Instructions For an Inexperienced Driller 1. Never run a bit too long a time. When a bit seems to be "good for one more run," discard it. 2. Always let the rods down on bottom easily. Protect the bit from sudden shock. 3. Start the drilling slowly and easily. Do not put pressure on the bit too fast. Diamonds can break. 4. Be sure the water pressure is strong enough to clear the bit, but do not use more water than is needed, as it may wash away the core. Usually, if no core is recovered the hole is a total loss. 5. When dry-blocking, do not run without water longer than necessary as the bit may burn. 6. Be sure the rods are well caulked and tightly screwed together. If not well caulked they will lose water, and if not

Jan 1, 1946

By D. R. Hay, E. Scala

Electrotransport has been superimposed on the rate-limiling- step in zone refining which is the impurity diffusion through the liquid at the solid/liquid interface. The efficiency of zone refining is increased and relative resistivity ratios (P300°k/P4 2°K) he increased by 50 pel in tungsten for a given number of posses using- the electrotransport field-aided method. The effiect of zotze refining in the presence of an electric field on the relative resistivity ratio is examined as a function of its intensity and polarity. THE effect of electrodiffusion on the effective distribution coefficient of zone refining has been discussed by Pfann and Wagner.' Control of the distribution coefficient in zone refining is of twofold interest. A distribution coefficient of unity can be increased or decreased, making possible the transfer of some previously inseparable solutes. The general efficiency of zone refining can also be increased. In the conventional zone-refining process impurities are removed by their retention in the molten zone and subsequent deposition at the end of the rod after a complete passage of the zone. In higher-melting-point systems a second mechanism may also operate, the volatilization of impurities from the molten zone. It has been suggested by schadler2 that, in refractory metals, vacuum distillation plays the predominant role in purification. In Koo's results,3 the resistivity ratio decreased beyond a zone-refined length of 6 in. from the starting end, indicating that some purification does in fact occur by true zone-refining action. Hay and scala4 showed that the degree of purity as measured by the relative resistivity ratio method depends on the square root of time in the molten zone (number of passes) and thus appears to be limited by diffusion in the boundary layer at the solidifying interface assuming good mixing in the body of the molten zone where a linear rate would prevail. The final concentration of impurities in electron-beam floating-zone purification depends very much on the operating conditions and results obtained by various investigators2,3,5 are difficult to correlate. The diameter of the starting material, operating vacuum, and rate of traverse are among the factors to be considered. There are, nevertheless, some general observations to be obtained from the literature. Lawley5 reviewed the literature up to 1962 and concluded that the major contaminants generally remaining in tungsten after electron-beam zone refining are molybdenum and carbon. Molybdenum due to its high melting point and distribution coefficient of nearly unity would be expected to be difficult to remove by either volatilization or zone refining. Carbon is not only a common contaminant in vacuum systems, but is also very difficult to remove by conventional vacuum melting. even with vacuums of 10-7 mm Hg. For each of those impurities removed by zone refining the equation of Pfann and Wagner may be applied: It relates the effective distribution coefficient k to a superimposed driving force which accelerates the solute away from the interface with a terminal velocity L" and to the more conventional zone-refining parameters; v = rate of traverse, t = thickness of the diffusion layer at the solidifying interface, D = diffusivity of the solute in the molten zone, and ko = equilibrium distribution coefficient of the impurity.

Jan 1, 1965

By Larry Kaufman, Morris Cohen

THE solid phase equilibria' and the martensitic transformation in the iron-nickel system have been the subject of considerable study. In addition, there have been numerous investigations on the calorimetric and thermodynamic properties of iron-nickel alloys. The purpose of the present work is to extend the existing information concerning the martensitic reaction in the iron-nickel system, and to develop a general thermodynamic treatment which will encompass the equilibrium and non-equilibrium phase

Jan 1, 1957

By E. C. Harder

AT a Meeting of the New York Section, on May 23, 1918, the sole subject of discussion was the nature and occurrence of iron ores in certain parts of the world.? Owing to the importance of this subject, it has been deemed' advisable to publish the remarks made at that meeting in the form of a paper, for presentation at the Milwaukee Meeting, instead of in the usual place, under News of Local Sections. The remarks related to the following districts: Brazil, by E. C. Harder, of the U. S. Geological Survey; Scandinavia, by Waldemar Lindgren, of the U. S. Geological Survey; Cuba, by C. M. Weld, of the U. S. Bureau 'of Mines; Southern Europe, by A. C. Spencer, of the U. S. Geological Survey; China, by H. Foster Bain, of the U. S. Bureau of Mines; Alsace-Lorraine, by Sidney Paige, of the U. S. Geological Survey. BRAZIL By E. C. Harder During the years immediately preceding the war, the iron ores of Brazil were attracting the attention of iron operators both in Europe and in the United States. This was clue to the large quantities of practically undeveloped ore available, and to its great purity. It is reasonably safe to state that had capital not been diverted from the exploitation of these deposits to war purposes, Brazilian iron ores would probably now be offered in European and American markets. It is certain that after the war these ores will play a prominent part in the economic reconstruction of Europe and perhaps in the development of America.

Jan 9, 1918

By Arthur E. Bousu, C. T. Eddy, L. W. Eastwood

The recrystallization and grain-growth phenomena of cold-worked metals have considerable industrial importance because of their role in the fabrication of metals. For this reason, and because of the general academic interest in the subject, these processes have received considerable attention since the time of J. E. Stead's paper1 on The Crystalline Structure of Iron and Steel. There are considerable differences of opinion regarding the theory of recrystallization and grain growth and also differences in the observation of the modus operandi of the processes themselves. The value of many of the existing quantitative data on grain growth is decreased by the failure to distinguish between the grain sizes just after complete recrystallization and those resulting from coalescence. For this reason also, the value of the diagrams of stable grain sizes, like those produced by Bass and Glocker2 and Czochralski3, is lessened in so far as an interpretation of the facts of recrystallization is concerned. It is hoped that the data presentcd in this paper will help to clarify and to simplify the facts relating to recrystallization, and at the same time will show that some of the present-day conceptions are untenable. A paper on the theory of recrystallization, with additional data, will be completed in the near future by the writers. Since the literature on the subject has been adequately and frequently reviewed, the only referenccs to it in this paper will be those necessary in the discussion of the data presented.

Jan 1, 1935