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By Herbert H. Uhlig

A STUDY of passivity in chromium-iron alloys holds considerable interest, both because of the present-day practical importance of the stainless steels, and because of the scientific importance attached to the mechanism of their corrosion resistance. Upon the discovery of the passive chromium-iron alloys in 1912, it seemed logical to attribute the observed phenomenal corrosion resistance to a thin, continuous, protective reaction product on the surface. The product was thought to be Cr2O3 or a similar oxide containing both chromium and iron. This mechanism seemed likely in view of Michael Faraday's conjecture that passive iron is not reactive in concentrated nitric acid because of an oxide on the metal surface.† Since 1912, data have accumulated that permit a further exploration into the nature of passivity and provide a new approach to the problem. A summary of the facts lends considerable weight to a mechanism based not on physical protection of an oxide or similar compound, although such compounds may be present on the surface, but to a change in tendency of surface metal atoms to react chemically. This change in reaction tendency is ascribed to chemisorbed films that effectively satisfy residual valence forces of the metal surface, but do not appreciably disturb the positions of metal atoms in the lattice. In other words, formation of a new lattice such as that of an oxide is not a necessary condition for this type of passivity. The decreased reaction tendency of the metal by reason of chemisorbed films can thereby account for low reaction rates of the stainless steels in many media, as well as a noble galvanic potential as is observed. Substances capable of adsorbing on the stainless steels, and hence accompanying the property of passivity, are typically oxygen, nitrites or chromates, but are not in any sense limited to these. Other elements and compounds can also chemisorb, and therefore may also play a major part in the mechanism of passivity in specific media. The mechanism of passivity based on chemisorption or activated adsorption begins with the interpretation Langmuir proposed for his experiments concerning adsorbed oxygen on tungsten.1 He found that adsorbed oxygen was tightly bound, remaining on the tungsten surface above temperatures at which WO3 rapidly volatilizes. The oxygen in such a state did not readily react with hydrogen even at

Jan 1, 1947

By Francis Donaldson

The direct injection of cement grout into water-bearing fissures as a means of checking or stopping the flow of water into shafts and tunnels has been experimented with for a decade or longer and seems to have been first attempted in Europe. The earliest application of which the writer has found a record was at a shaft sunk by the Mining Society of Lens; this is described by C. Dinoire in the Transactions of the Institution of Mining Engineers.1 It is only lately, however, that the process has been entirely successful. This success has been accomplished on the Catskill Aqueduct, now under construction by the city of New York. This aqueduct includes a number of deep pressure tunnels, reached by shafts for both waterway and construction purposes. In portions of these shafts and tunnels considerable underground water was met. The contract for the first of these deep pressure tunnels was let to the T. A. Gillespie Co.; this section is known as the Rondout Siphon. It leads under the Rondout valley at a depth of from 400 to 800 ft. and is about 5 miles long. The engineers expected that considerable water would be encountered, but fortunately this was not the case except at one shaft, known as No. 4, which penetrated the rock at a junction between limestone and conglomerate. Water-bearing fissures were encountered almost immediately. At a depth of about 200 ft. a flow of 1,500 gal. per minute was struck. The. shaft then contained as many pumps as could be used, and it seemed impossible to sink it further. After vain efforts had been made to proceed, John P. Hogan, a division engineer of the Board of Water Supply, suggested that cementation of the fissures be tried. The process was attempted for the first time in this country. Since the shaft was partly full of water it was necessary to drill grout holes with a diamond drill. Platforms were placed on the timbers at the water level, the diamond drill was installed and six 90-ft. holes were drilled in the bottom of the shaft. Several car loads of cement were pumped through these holes into the fissures, the drill casings being used for grout pipes. This largely cut off the flow of water from, the bottom and sinking could then

Jan 1, 1915

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' 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' 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

By D. Turnbull

RECENTLY it has been shown that aggregates of small liquid droplets of tin,' mercury' or gallium' kept from intercommunicating by suitable films do not solidify at an appreciable rate unless the supercooling is very much greater than that usually necessary to cause a large continuous mass of the metal to solidify. For example oxide-coated tin droplets1 (1 to 10 micron diam) must be supercooled 100" to 110°C before their rate of solidification becomes rapid, although large continuous masses of liquid tin usually begin to solidify when supercooled 30" or less." These experiments have been interpreted' on the hypothesis that nucleation of crystals in large continuous metal samples is almost always catalyzed by accidental inclusions. Therefore, if the metal is dispersed into a number of isolated droplets large in comparison with the number of inclusions, most of the droplets should not crystallize until a temperature sufficiently below the thermodynamic melt- ing point, T0, has been reached to permit an ap-preciable rate of homogeneous (noncatalyzed) nu-cleation. In general this temperature is very much less than the temperature at which the rate of heterogeneous (catalyzed) nucleation is appreciable. If this interpretation is correct then investigation of the kinetics of crystallization of small droplet aggregates should be one of the most fruitful methods of obtaining information about the homogeneous formation of crystal nuclei in liquids. In this paper the results obtained on gallium and mercury are reported more fully. In addition, results on the supercooling of aggregates of liquid bismuth and lead droplets are included. Experimental Procedure Some care must be exercised in the choice of a barrier to prevent the liquid droplets from coalescing lest the barrier itself catalyze the formation of crystal nuclei. From this standpoint, the most desirable barrier is vacuum or inert gas, but, because of the difficulty of experimental arrangement, solid compounds and adsorbed films have been selected. There are two guiding principles in the selection of compounds as barriers in addition to the requirement that they prevent coalescence of liquid droplets. First, the compound should be almost insoluble in the liquid metal and second, its lattice structure should be quite unlike that of the forming metal crystal. Even so, there is no a priori assurance that the solid compound film will not catalyze to some extent the formation of metal crystal nuclei. An adsorbed protective monolayer is less likely to be catalytic than a crystal compound film, but it is not often possible to find a monolayer that is stable under the experimental conditions. Also, it is desirable, though not generally essential, that the aggregate of droplets be prepared by breaking up the massive metal rather than from a powdered compound of the metal.

Jan 1, 1951

By M. Gensamer

IN applied mechanics and in metallurgy the transition from elastic to inelastic action is a matter of considerable interest and importance. Often the first inelastic deformation is apparently quite homogeneous; that is, uniformly distributed throughout the specimen. Sometimes this deformation is heterogeneous; that is, localized; inelastic deformation proceeds to some definite amount in restricted regions before adjacent regions of the specimen are inclastically deformed. In such cases the deformation does not become homogeneous until the whole specimen has been deformed the amount corresponding to that for each localized deformation. If the test is stopped before uniform extension sets in, the heterogeneous character of the deformation is apparent on the surface of the specimen through characteristic markings, which have been called "Lüders"' lines, "Hartmann's" lines, the "Piobert effect," or simply "flow figures." These markings are the source of considerable trouble in fabricating operations, particularly in the deep drawing of steel sheet. In many cases where the transition is of this nature, the stress developed at the upper limit of the elastic range is greater than the stress during the period of heterogeneous deformation, giving rise to the familiar "drop of the beam" effect in testing. The amount of the yield-point elongation, as well as the value of the stress at the lower yield point (the value to which the stress drops when yielding begins), are functions of the tempera-ture and the testing speed. Lower temperatures and faster rates of testing increase both the yield-point elongation and the yield-point stress. These matters have been ably discussed in a recent paper by Winlock and Leiter1 though, as brought out by the discussion of that paper, the phenomena are but little understood. The purpose of the present paper is to clarify the problem through the application of a simple principle, and to show that, through the application of this principle, a number of phenomena in the plastic deformation of metals become more read-ily understood.

Jan 1, 1938

By C. Gatlin, F. Armstrong, K. E. Gray

This paper presents some preliminary results of two-dimensional cutting tests of dry limestone samples at utmospheric pressure. Cutting tips having rake angles of + 30°, + 15", 0°, - 15" and - 30" were used to make cuts on Leuders limestone samples at six depths of cut ranging from .005 to ,060 in. at cutting speeds of 15, 50, 109 and 150 ft/min. The vertical and horizontal force components on the cutting tips were recorded with an oscilloscope equipped with a polaroid camera. Motion pictures of the cutting process at camera speeds of 5,000 to 8,000 frames/sec were taken at strategic points in the variable ranges. The movies provide considerable insight into the brittle failure mechanism in rocks. It appears that chip-generating cracks usually have an initial orientation which is related to the resultant of the externally applied forces. The latter part of the crack curves upward toward the free surface being cut, this part being governed by some type of cantilever bending or prying. The linear and angular motion of the loosened chips also indicate the tensile nature of brittle failure. Analyses of the forces on the cutting tips indicate that: (I) relatively small increases in vertical loading result in large cut-depth increases for sharp tips (rake angles 2 0"); (2) tool forces increase at an increasing rate as the rake angle decreases, particularly for rake angles < 0"; and (3), for the range of this study, rate of loading had little effect on the maximum forces. Both the movies and visual inspection of the cuttings indicated that the volume of rock removed by chipping was much larger than that by any grinding mechanism, even for tips having negative rake angles. Cutting size increases with increased cut depth and rake angles, and decreases slightly at high cutting speeds, the depth of cut having by far the most influence. The amount of contact between the rock and the cutting tip was always less than the depth of cut and rarely exceeded 0.010 in. even for cuts of 0.060 in. INTRODUCTION The planing (or slicing) of various materials with a fixed blade has long been practiced by workers in many industries. For example, the farmer&apos;s plow, the carpenter&apos;s plane and the housewife&apos;s paring knife all employ this basic action. The casual observer might suspect that something so common must be quite simple; however, as in all problems involving the failure of materials, such is not the case. Industries concerned with the machining of metals have long studied these problems, and their literature on the subject is voluminous. Despite these efforts, basic knowledge is not very advanced, as may be noted from recent and comprehensive analyses of their literature.12 Metals are more subject to analysis by classical theories of elasticity and/or plasticity than are rocks, since their elastic constants and strengths are reasonably well established in many cases. In spite of this relative "simplicity", Hill9 refaces his discussion with an admission that the mathematical solution to the machining problem is not known. Photoelastic studies of both machining and milling have been performed and are discussed thoroughly by Coker and Filon.4 Rotary drilling of rocks with fixed blade or drag bits has long been practiced by the mining and petroleum industries, and considerable study has been given to defining their cutting action in terms of the pertinent variables. Essentially all the published mechanistic research on drag-bit drilling has been performed by mining engineers and has been concerned only with rocks in the brittle state. Fairhurst5-7 has worked extensively in this area and employed photographic techniques quite similar to those reported here, except at much lower speeds. His studies showed the periodic or cyclical nature of the brittle failure mechanism, in which instantaneous loads on the bit varied from some maximum value to near zero. Goodrichs has presented further data on the subject as well as a qualitative description of the process. Again the postulated mechanism is cyclical, with alternate chipping and grinding periods. The ploughing of coal is a practiced method and has been studied in some detail by English mining engineers."" Their findings have considerable general application to drag-bit drilling. Evans," in particular, has extended Merchant&apos;s metal-cutting theory" to brittle materials with some success, although certain aspects of his theory are open to question. Fish13 has recently summarized nearly all the published works concern-

By Francis Donaldson

THE direct injection of cement grout into water-bearing fissures as a means of checking or stopping the flow of water into shafts and tunnels has been experimented with for a decade or longer and seems to have been first attempted in Europe. The earliest application of which the writer has found a record was at a shaft sunk by the Mining Society of Lens; this is described by C. Dinoire in the Transactions of the Institution of Mining Engineers.1. It is only lately, however, that the process has been entirely successful. This success has been accomplished on the Catskill Aqueduct, now under construction by the city of New York. This aqueduct includes a number of deep pressure tunnels, reached by shafts for both waterway and construction purposes. In portions of these shafts and tunnels considerable underground water was met. The contract for the first of these deep pressure tunnels was let to the T. A. Gillespie Co.; this section is known as the Rondout Siphon. It leads under the Rondout valley at a depth of from 400 to 800 ft. and is about 5 miles long. The engineers expected that considerable water would be encountered, but fortunately this was not the case except at one shaft, known as No. 4, which penetrated the rock at a junction between limestone and conglomerate. Water-bearing fissures were encountered almost immediately. At a depth of about 200 ft. a flow of 1,500 gal. per minute was struck. The shaft then contained as many pumps as could be used, and it seemed impossible to sink it further. After vain efforts had been made to proceed, John P. Hogan, a division engineer of the Board of Water Supply, suggested that cementation of the fissures be tried. The process was attempted for the first time in this country. Since the shaft was partly full of water it was necessary to drill grout holes with a diamond drill. Platforms were placed on the timbers at the water level, the diamond drill was installed and six 90-ft. holes were drilled in the bottom of the shaft. Several car loads of cement were pumped through these holes into the fissures, the drill casings being used for grout pipes. This largely cut off the flow of water from the bottom and sinking could then

Jan 1, 1914

By Marston G. Fleming

CRITICAL pH has been defined by Wark1 as that pH value below which a mineral will float and above which it will not float in solutions containing a given concentration of collector but free from other depressants or activators. - The relationship between mineral, collector concentration, and pH is expressed in the form of a critical pH curve determined by the captive bubble method and is generally regarded as being fundamental to the system involved. The mechanism of alkali depression is currently in dispute, two general theories having received authoritative support. The view expressed in Taggart&apos;s chemical theory of flotation2 is that in the presence of a critical concentration of hydroxyl ions, all the metal ions available at the surface of the mineral are present as anions of the form [M (OH)x]-y. The formation of the necessary metal xanthate is thus precluded and, furthermore, any metal xanthate coating previously formed, at a lower pH, will be dissolved. Gaudin3,4 and the Melbourne school under Ware hold that alkali depression is caused by the preferential adsorption of hydroxyl ions by the mineral surfaces. This paper describes an investigation of the mechanism of alkali depression in each of the three systems: cerussite-aqueous carbonate-xanthate, cerussite-xanthate, and galena-xanthate. Alkali Depression of Cerussite by Control of Carbonate Ion Concentration Wark and Cox6 have shown that in the presence of Na2CO3 a higher concentration of xanthate is required to effect bubble contact with a cerussite surface than in carbonate-free solutions. To examine this depression of cerussite by sodium carbonate, a series of captive bubble tests was carried out on cerussite specimens in solutions containing 100 mg per liter of potassium ethyl xanthate and varying concentrations of sodium carbonate. The pH was adjusted by the addition of dilute hydrochloric acid. For purposes of comparison a standard critical pH curve was determined for cerussite with potassium ethyl xanthate in solutions containing no added carbonate. In the latter case pH adjustment was made with sodium hydroxide. The experimental method employed in both series was broadly similar to that described by Wark and Cox;7-9 a number of refinements suggested by Sutherland10 were adopted, and the procedure was further developed and modified to suit the particular requirements of the investigation. The relationship between pH and the concentration of potassium ethyl xanthate necessary to induce bubble contact at cerussite surfaces is shown in Fig. 1. The relationship between pH and the concentra- [ ] tion of sodium carbonate necessary to prevent bubble contact at cerussite surfaces in the presence of 100 mg per liter of potassium ethyl xanthate is shown in Fig. 2. Comparison of the. two curves shows that at a collector concentration of 100 mg

Jan 1, 1952

By James Malcolmson

(New York Meeting, February, 1913.) THE Tigre Mining Co. of Mexico, owned by the Lucky Tiger Combination Gold Mining Co. of Kansas City, decided early in 1910 to enlarge its mill, which consisted of a concentrator milling 3,000 tons of ore per month. The enlarged plant was designed to crush and concentrate 6,000 of ore and to cyanide 7,500 tons per mouth. The extra tonnage cyanided was to be obtained from tailings which were stored below the old mill. Power was supplied to the old mill from four boilers; a 150-h-p.. Corliss engine and two Weber 60-h-p. gas-engines using producer-gas made from charcoal. The total horse-power required, including 60 h-p. used for machine-drills in the mine, was approximately 275. Cord-wood cost $4.32 per cord, 8 by 4 by 3 ft., and charcoal $15 per ton. The fuel supply in the surrounding country was approaching exhaustion; more than 150 mules and 50 men were engaged in cutting and transporting this fuel, and the unsettled political, conditions in Sonora were such that it would be practically impossible to keep an organization of this kind together. The price of fuel was steadily rising and at times it became almost impossible to get sufficient fuel to operate.

Jan 4, 1913

By H. W. Page

Petroleum requirements since V-J day have been appreciably higher than predicted. Foreign operations now exceed maximum wartime levels by about 14 per cent. Domestic operations since V-J day have averaged 92 Per cent of the wartime peak. In spite of maximum foreign refinery runs, large exports of all products, except residual fuel oil, are necessary to meet foreign demand. During the next few years it is expected that foreign operations will continue at capacity, including new installations, but that, because of increases in foreign demand, exports will continue at about their present level. Domestic operations will increase during this period and crude production probably will exceed maximum efficient rates. Even after 10 years some exports probably will be required, but eventually these will be supplanted by increased output of foreign refineries, except for small tributary exports. The increase in domestic requirements will exceed the decline in exports. Unless findings of crude oil exceed present expectations, the increasing demand will be met by increased imports and synthetic methods-—such as the Hydrocarbon Synthesis Process for conversion of natural gas and coal to gasoline and distillates. Catalytic cracking installations will increase as crude availability decreases. This will help to meet the increasing demand for gasoline but will intensify the domestic shortage of residual fuel oil. Eventually larger imports will be required to satisfy the demand for this product. Introduction Under the pressure of the wartime period, there was time only occasionaly to look ahead in anticipation of what the postwar era held for the petroleum industry. Perhaps the general expectation was that a rather pronounced decline in the level of industry petroleum operations would take place shortly after the end of the war, with the impact felt mainly on the economy of the United States- It is of interest now, nine months after V-J day, to take inventory of the near-term situation and see what significant forces are at work. With this as a starting point, it should be possible to engage in something more satisfactory than pure speculation concerning trends in the immediate future and 10 to 20 years ahead. Present and Near-term Situation During the nine-month period following V-J day, foreign crude oil production and rebery operations have actually increased the These activities were at maximum capacity on V-J day but the continuation of drilling programs, the completion of new and rehabilitated refineries and of transportation facilities during the Past nine months have increased the foreign capacity. This added capacity has been fully utilized. Foreign crude oil production in May 1946 is about 14 per cent higher than during July 1945 and refining operations some 12 per cent higher&apos; During the same period there has been a falling off in similar activities within the

Jan 1, 1947

By H. W. Page

Petroleum requirements since V-J day have been appreciably higher than predicted. Foreign operations now exceed maximum wartime levels by about 14 per cent. Domestic operations since V-J day have averaged 92 Per cent of the wartime peak. In spite of maximum foreign refinery runs, large exports of all products, except residual fuel oil, are necessary to meet foreign demand. During the next few years it is expected that foreign operations will continue at capacity, including new installations, but that, because of increases in foreign demand, exports will continue at about their present level. Domestic operations will increase during this period and crude production probably will exceed maximum efficient rates. Even after 10 years some exports probably will be required, but eventually these will be supplanted by increased output of foreign refineries, except for small tributary exports. The increase in domestic requirements will exceed the decline in exports. Unless findings of crude oil exceed present expectations, the increasing demand will be met by increased imports and synthetic methods-—such as the Hydrocarbon Synthesis Process for conversion of natural gas and coal to gasoline and distillates. Catalytic cracking installations will increase as crude availability decreases. This will help to meet the increasing demand for gasoline but will intensify the domestic shortage of residual fuel oil. Eventually larger imports will be required to satisfy the demand for this product. Introduction Under the pressure of the wartime period, there was time only occasionaly to look ahead in anticipation of what the postwar era held for the petroleum industry. Perhaps the general expectation was that a rather pronounced decline in the level of industry petroleum operations would take place shortly after the end of the war, with the impact felt mainly on the economy of the United States- It is of interest now, nine months after V-J day, to take inventory of the near-term situation and see what significant forces are at work. With this as a starting point, it should be possible to engage in something more satisfactory than pure speculation concerning trends in the immediate future and 10 to 20 years ahead. Present and Near-term Situation During the nine-month period following V-J day, foreign crude oil production and rebery operations have actually increased the These activities were at maximum capacity on V-J day but the continuation of drilling programs, the completion of new and rehabilitated refineries and of transportation facilities during the Past nine months have increased the foreign capacity. This added capacity has been fully utilized. Foreign crude oil production in May 1946 is about 14 per cent higher than during July 1945 and refining operations some 12 per cent higher&apos; During the same period there has been a falling off in similar activities within the

Jan 1, 1947

By Waldemar Lindgren

Fifteen years ago, in his presidential address before the Washington Academy of Sciences,&apos; Alfred H. Brooks said: "Applied geology can only maintain its present high position by continuing the researches which advance the knowledge of basic principles. Future progress in applied geology depends on progress in pure geology. Early in 1927, Dr. David White, then chairman of the Division of Geology and Geography of the National Research Council, appointed a committee "On the Processes of Ore Deposition," which was the first recognition by the Council of this branch of applied geology. This committee will not be able to solve the many complex problems involved; it can only clear the way, survey the field, state the problems and encourage systematic research. This short paper aims to outline and to analyze the present status of this kind of geological research, to ascertain the quality of the work and to suggest lines that might profitably be followed. Increasing Demand for Geologists Economic geology, or the art of geology, could develop only after the principles of geology and mineralogy had been established. Before that time it was merely a collection of trade rules accompanied by more or less wild speculations. Thus we observe the beginnings of economic geology in the period 1770-1820. Soon afterwards, the State Surveys were established in this country, with the realization that the natural resources should be investigated and described. Geology was hardly yet equal to the task of scientific research in relationships and genesis, however, and there followed a period of discouragement and stagnation. In the meanwhile, pure geology had again registered progress, and, based on its principles and also on the rapid mining development in the Cordilleran region, the present phase of the study of ore deposits began to take form. Raphael Pumpelly, S. F. Emmons and G. F. Becker were among the pioneers in this movement. The United States Geological Survey was organized. Ore deposits were scientifically described and studied along lines of structure and mineralogy; theories of genesis were advanced, not always permanent but based on sound induction.

Jan 1, 1928

By Jack Washburn

The c axis indentations in zinc crystals were shown to undergo 100 pct strain recovery on heating. The mode of deformation and the details of the polygonization and collapse of indentations were found to be consistent with a number of predictions of dislocation theory. IT has been observed that indentations of the type made by Jillson in zinc crystals can, under certain conditions, be macle to shrink in size and even completely disappear on heating the crystal, Fig. 1. The details of the process are interesting in that they afford a simple experimental illustration of several predictions of dislocation theory. The indentations were made as shown in Fig. 2 by dropping a 0.2 g indenter with a hemispherical point on a cleavage face of a. zinc crystal. Such indentations can be made through relatively great thicknesses in the c-axis direction. The material close to the struck surface, where mechanical twinning and complex distortion occurred, was removed by cleavage. The remaining crystal, which was about 1 cm thick, contained a dent that was accurately round and almost the same size on both top and bottom surfaces. The indentation had the form of a flat cone of half angle approximately 89°, having a rounded apex and a rounded intersection with the unde-formed part of the crystal. The mode of deformation was primarily slip on the three equivalent systems in the basal plane. Six types of dislocation loop (plus and minus in each of the three directions) as shown in Fig. 3 are required by the geometry of the indentation. The maximum shear strain in the radial direction amounted to approximately 2.5 pct. Slip was distributed in the usual, microscopically nonuniform, manner among the possible parallel slip planes. When an indentation was made close to a (2110) surface, three separate sets of interpenetrating slip bands appeared as shown schematically in Fig. 3. A small biaxial tension strain in the plane of (0001) is also a geometrical necessity for the formation of an indentation. If the sides of the dent are tilted l° with respect to the undeformed surrounding crystal, and the surround-

Jan 1, 1957

By R. M. Hudson

A study has been made of the decarburization of low-carbon sheet steels at temperatures from 1100" to 1475°F in mixtures containing hydrogen, nitrogen, water vapor, and in some instances carbon monoxide. Decarburization occurs principally by the reaction C (in steel) + H20 = CO + H2 and follows a first-order rate law. The decarburization rate appreciably increases with an increase in temperature up to about 1325°F, but the increase in rate is small with fur- Use of a dry hydrogen atmosphere results in a relatively slow decarburization of steel and use of a wet hydrogen atmosphere results in relatively rapid decarburization. It is now generally recognized&apos; that the reaction C (in steel) + H2O = H2 + CO [l] accounts for most of the decarburization that occurs in wet hydrogen-containing atmospheres. The present article is concerned with the decarburization of low-carbon sheet steel in H2-N2 atmospheres ther increase in temperature. The limiting rate of decarburization can be predicted from a knowledge of the solid solubility and diffusivity of carbon and this rate is approached as the water-vapor content of an atmosphere is increased. Hydrogen contents above about 8 pct are beneficial only in that they permit higher levels of water vapor to be used without oxidation of the steel. A buildup of CO in the atmosphere lowers the rate of decarburization. containing various amounts of water vapor and carbon monoxide. The effectiveness of these atmospheres and the influence of temperature on decarburization rate will be considered. EXPERIMENTAL WORK The chemical compositions of the three steels used in decarburization-rate studies are listed in Table I. Steel A was a commercially hot-rolled rimmed steel that was cold-reduced at the Laboratory to furnish specimens 0.025, 0.041, and 0.059 in. thick. Most of the experiments in which this steel was used were made on the 0.041-in.-thick material. Steel B and Steel C were cut from 0.010-in.-thick commercially cold-reduced coils that were

Jan 1, 1963

J. E. JOHNSON, JR., New York, N. Y. (communication to the Secretary*).-The discussion of Mr. Henrich&apos;s paper took place at a meeting from which I had the misfortune to be absent, and has just come to my attention. I do not wish to let the subject pass without contributing to it a little information which has come into my possession. In 1912, I published a brief note in the Transactions on The Effect of Alumina in Blast-Furnace Slags, giving in tabular form three typical slags used in iron blast-furnace practice, one of them the high alumina slag of, which Professor Richards speaks. That table is reproduced herewith. TABLE 1.-Composition of Slays. 1 3 3 4 5 6 7 CaO by Neutral Ratio Ratio Ratio Al2z03, SiO2, Differ- Substan- Cat Ca0 a A1203 Ratio Per Per ence, ces, CaO Cent. Cent. Per Per Al2O3 + Sioz Sit: SiO2 Cecil_ Cent. Virginia practice 6.5 36.0 54.0 3.5 1.27 1.6S 1.50 Lake-ore practice 13.5 33.0 50.0 3.5 1.08 1.92 1.51 Special experiment... 36.0 24.7 36.8 3.5 0.59 2.90 1.44 It supplies what seems to me convincing evidence that, for the purposes of the iron blast furnace, alumina can be regarded only as a neutral substance, dissolving in the slag and materially altering its viscosity, but not affecting its chemical activity. In subsequent experience with charcoal furnaces, I found the same rule to hold; that the chemical effect of alumina could be disregarded, providing the ratio of the lime and magnesia to the silica were kept constant. This is exactly the experience which Messrs. Dwight and Mathewson had in copper- and&apos; lead-smelting furnaces. I have never seen any evidence or argument adequate to support the contention of Professor Richards-that the alumina acted as a base in the charcoal iron furnace and as an acid in the coke furnace, and that the function of alumina in iron-furnace slags is inherently different from that in copper- and lead-furnace slags-and I am compelled to differ absolutely with his conclusions in that respect.

Jan 9, 1917

By F. A. Forward, J. Halpern

A new process is described for extracting uranium from ores containing sulphidic minerals, which comprises treating an aqueous pulp of the ore with air or oxygen at elevated temperatures and pressures. The acid required to dissolve the uranium is generated during the leach through oxidation of the sulphides. The chemistry of the process is discussed and laboratory results are presented to illustrate the operation of the method and the variables which control it. With most ores, leaching at a temperature of 130°C and an oxygen partial pressure of 10 psi provides uranium extractions of 90 to 95 pct in 4 to 6 hr. The acidity and level of dissolved impurities in the leach liquor can be kept fairly low. The method is characterized by a number of advantageous features including low reagent cost, short retention times, and high recoveries. RECENTLY there have been developed several processes for extracting metal values from ores by pressure leaching techniques;&apos; -&apos; an example is the carbonate leaching process for uranium ores which has been studied in this laboratory.&apos; Leaching is carried out under oxygen pressure to ensure oxidation of the uranium to hexavalent compounds which are soluble in carbonate solutions. During the course of investigations relating to this process, it was observed that sulphide minerals, such as pyrite, usually were oxidized under the conditions of the leach treatment resulting in the formation of iron hydroxides and sodium sulphate, i.e. 2 FeS= + 7Vz O2 + 8 Na,CO3 + 7 H,,O -* 2 Fe(OH)3 + 4 Na2SO4 + 8 NaHCO.,. [1]

Jan 1, 1956

By W. C. Lilliendahl, G. Meister

Uranium metal with a purity of about 99.9 pct was produced on a large scale by fused salt electrolysis with a material efficiency of about 90 pct. The material efficiency depends mainly on bath composition, electrolysis temperature, electrode smothering, and elutriation during washing of the powder. RESEARCH and development work on fused salt electrolysis carried on by the Westinghouse Lamp Div. Bloomfield, N. J., was done under the Manhattan District Corps of Engineers and later under the Atomic Energy Commission for the commercialization of uranium production for the first atomic pile at the University of Chicago in 1942. From the conception of the atomic bomb project it was recognized that metals with impurity levels having little metallurgical significance would be required. Permissible impurity levels were based on neutron absorption. Of particular significance was boron, which could not be present in amounts exceeding 1 ppm. The electrolytic method as developed in 1930 by Driggs and Lilliendahl,1,2 and later improved, yielded uranium of very low boron and other deleterious impurity content. No other method was capable at that time of producing uranium metal of the required purity.&apos; The low boron content of uranium produced by the electrolytic process resulted from the availability of the reactants which were low in boron content, and from the inherent elimination of boron in the fused salt bath. Since the heart of any electrolytic process is the electrolysis cell, this paper will deal with the development of the original bath composition for the efficient production of uranium from a batch process to one of continuous operation. Emphasis also will be placed on other factors which will affect the material efficiency of the process. With the laboratory cell the material efficiency of uranium powder recovery in the early electrolysis was relatively low, about 35 pct based on the ratio of uranium recovered to uranium added. This early process also had other defects. The electro- lytic bath could not be used continuously. After three runs from a freshly charged crucible, the deposit showed a tendency to slip off the electrode as it was raised from the bath. This condition necessitated pouring the charge every fourth run and preparing a new bath. It was assumed at that time that this condition was caused by the increasing fluoride concentration with each addition of uranium salt, which adected the mobility of the uranium ions. Experimental The electrolysis cells differed in size only. They were of the floating cathode type. The laboratory cells were 21/2 in. ID and 6 in. deep and operated at 30 amp and 5 volts. Production was about 150 g metal powder per 8 hr. The plant cells (5 units) were 9 in. ID x 21 in. deep and operated at 1800 amp at 12 volts. The total production unit was designed to produce 250 lb of uranium powder per 8 hr day. Because of the tendency of uranium fines toward spontaneous combustion, material efficiencies were based only on the recovery of useful coarser metal which could be safely handled. The reported efficiencies are of particular significance only as related to the same group of experimental procedures. At the start of the project no changes were contemplated until previous data could be definitely confirmed. Therefore, the first experiments were with the 50 pct CaCl2-50 pct NaCl mixture. The material efficiency of uranium deposition as a function of the number of electrolyses is shown in Table I. In Table I, the decrease in efficiency at 800°C with number of runs is apparent and confirmed the earlier data. Operating at 900°C enabled the number of runs to be doubled, but before pouring the charge the efficiency of recovery became poor. This test indicated that the improved efficiency might have been caused by an increase in the fluidity of the bath.

Jan 1, 1958

By Ionel I. Gardescu

During the summer of 1930 the average daily oil production of Rumania registered a new peak at 128,000 bbl. per day. The estimated potential production as of September, 1930, was as high as 235,000 bbl. per day. During the latter part of the year, by mutual agreement, the operators decided to curtail their output to about 100,000 bbl., which brought the average for the year to 116,600 bbl. The total production for 1930 was 41,572,000 bbl. (last month estimated) as compared with 35,757,000 bbl. for 1929, or an increase of 16.3 per cent. over last year&apos;s production. The production for the last 10 years is given in Table 1. The curtailment of production was prorated per company, based on its total estimated potential production as of September, 1930, and not per field. As a consequence, at present there is little development of protected or slightly productive areas; viz., Arbanasi, with an average production of 1750 bbl. per day, dropped to less than one-third after curtailment came into effect. Moreni, with an average production of 92,000 bbl. per day, while producing 58 per cent. of the country&apos;s total output in 1929, went to 67 per cent. at the beginning of 1930 and to 75.2 per cent, towards the end of the year. The modified Mining Law of 1929 is still in effect. This law withdraws the restrictions set on foreign capital by the law of 1924. As a consequence a large percentage of proven state land was alloted through competitive bidding to foreign companies. The Romano-Americana (Standard of New Jersey) acquired several leases in the Boldesti and

Jan 1, 1931

Discussion of the paper of F. E. Lucas, presented at the Cleveland meeting, October, 1912, and printed in Bulletin No. 71, November, 1912, pp. 1315 to 1326. F. Louis GRAMMER, Leesburg, Va. (communication to the Secretary *):--Mr. Lucas&apos;s paper reminds us of our extravagance in coking, and our tardiness in the adoption of by-product ovens, as compared to Germany. We are, however, so rich in coal-having mined, so far, less than 1 per cent. of our known national resources-that the argument of conservation is not very pressing. It is true that our so-called coking-coal beds are not inexhaustible; but by-product ovens coke coal that bee-hive ovens cannot handle, and so really enlarge our reserves of coking coal. " Conservation of Resources " is a phrase in great vogue. It is overworked and abused at times; being used by those who desire to be the exclusive custodians of resources or the sole purveyors of commodities. It does not carry great weight as regards coal. There are, however, aside from the attractive considerations of profit set forth by Mr. Lucas, several other important reasons why by-product ovens should be introduced more widely. One is that coal-tar pitch is the keynote to the extension of the coal-briquette industry. The more coal-tar pitch is available, the more briquetting will be carried on; and this will utilize much coal which is either waste or a drug in the market. Heretofore, in several instances coking and steel-making plants have been built, primarily, to market bituminous slack.

Jan 5, 1913

By R. Kossowsky

USING etch-pit techniques, Johnston and Gilman&apos; have shown that the stress dependence of dislocation velocity can be represented by the expression where r, is the dislocation velocity, a is the applied stress, and oa, is the stress to produce a unit velocity. Noble and Hul12 showed that the exponent m is strain-dependent and increases rapidly in the work-hardening region. This was explained by arguing that in the work-hardened material the applied stress required for any given velocity will be greater than in the annealed material by an amount equal to a back stress due to work hardening. schadler3 has stressed the importance of substructure as a possible source of error in dislocation velocity measurements, and took care to make velocity measurements in which dislocations moved such short distances that interactions with boundaries were avoided. schadler3 also pointed out that, if standard testing equipment is used, measurements of m from flow stress data could be seriously in error in materials with a high initial work-hardening rate. Noble and Hu112 have further argued that, due to the strain dependence of m , the extrapolation to zero strain4 to obtain the true value of m can be justified only in the preyield region. Microstrain experiments in high-purity iron5,6 have led to the conclusion that aiA (Ref. 5) (defined as the stress to first produce a permanent set of 10-6 in. per in.) and oflow are not controlled by the same deformation mechanism. It has been proposed5,6 that aA is governed by the lattice resistance to the motion of screw dislocations in a given slip plane and that oflow is controlled by the lattice resistance to a full-scale cross slip. The purpose of this note is to extend Noble and Hull&apos;s argument further and to show that measurements of m from flow stress data can be in error due to the rapid increase in stress in the microstrain region6 when stress is increased beyond aA. Double z-one-refined single crystals of molybdenum (with the (101)[ 111] slip system operating and a Schmidt factor of 0.475) were used in an experimen-

Jan 1, 1968