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By B. S. Norris, Charles R. Austin

The stresses which initiate deformation processes in metals are fundamentally important in the study of the mechanical properties of metals. A point of inflection in the load-elongation curves obtained for single crystals' has been rather too readily interpreted as a true yield point, and the critical resolved shearing stress on the plane of slip taken as a material constant. Even early work showed that the stress at this point varies with rate of loading, but it has not been generally appreciated that creep tests under static loads alone are suited for determining the existence or nonexistence of a yield point.* It has now been shown by Miller that single crystals of zinc3 when loaded statically begin to yield at loads too small to measure; as a result there is no case now known, apart from that cited in the present paper, in which a true critical stress for yielding has been demonstrated for single crystals of metals. The case of iron has especial interest: the existence of an upper and lower yield point and of an elongation at the yield point in ordinary iron and steel marks this substance as unusual, though the effects have been found to a very minor degree in other metals and alloys. $ Most alloys do not show such marked phenomena when appreciable yielding begins, and accordingly modern practice is to speak of the yield strength of such materials, a stress read from the load-elongation curve after elongation has begun, rather than yield point. The special behavior of iron suggests that it is more likely that single crystals of iron should have a true yield point than other metals. The study of the mechanical properties of metals and alloys requires a determination of the crystallographic mechanism of deformation, wlletller deformation proceeds by slip, twinning, or cleavage, or a combination of these, and a determination of the stresses that induce these modes of deformation. With this information, a study of the rates of work-

Jan 1, 1938

By P. T. Chiang

Chemical etching methods for the simultaneous revealing of the tellurium or selenium Phase and the chalcogenide grain boundaries of the alloy systems are given. A tellurium eutectic was found Present in zone-melted ingots. Similarly, a selenium monotectic was present in ingots. In general, the second phase (tellurium or seleniumn) occubies three different sites; viz., along the chalcogenide grain boundaries, as inclusions within the chalcogenide grain, and on the undersurface of the ingot. The detection limit for the tellurium phase is about 1 u in width. THERMOELECTRIC materials based on Group V (bismuth, antimony) and Group VI (selenium, tellurium) elements have aroused considerable interest in recent years in the practical application of thermoelectric cooling. In many cases, a small amount of excess tellurium (or selenium) was added to the material to optimize its thermoelectric properties. Then the question immediately arises as to the number of phases present in the resultant alloy. In the binary systems of Bi-Te, Sb-Te, and Bi-Se, the congruent melting compositions have been reported to be non-stoichiometric and are represented by Bi~Te respectively. It is to beexpected and known that Bi2Te3 and SbzTe3 crystallize from the melt with an excess of bismuth and antimony in the lattice and that tellurium forms a eutectic.~' The same could be assumed to take place in the pseudo binary systems of (Bi,Sb)zTe3 and Bi2(Se,Te)3 as well as in the system studiedby puotinen5 and other workers. Likewise, BiaSe3 crystallizes from the melt with an excess of bismuth in the lattice and selenium forms a monotectic.~ Therefore, in practice, alloys solidified from the melt often contain a second phase (tellurium or selenium) in one region or another of the solid mass even without the addition of excess tellurium (or selenium). ~u~~recht' studied the thermoelectric properties of (Bi,Sb)2Te3 alloys with excess tellurium and simultaneous additions of selenium. He mentioned that the materials show two phases because of the considerable excess of tellurium or selenium. However, he did not report as to how the tellurium or selenium phase was identified. It is generally believed that the presence of an excessive amount of tellurium or selenium phase in the alloy would adversely affect its thermoelectric properties and its uniformity. Consequently, there is a need for a simple method for the identification of the tellurium and selenium phase. The quantity of the second phase present is usually too small to be detected either by chemical analysis or by normal X-ray techniques. This investigation was therefore carried out, first, to devise a simple metallographic method for the identification of the tellurium or selenium phase coexisting with the chalcogenides and, second, to determine the distribution and specific location of the tellurium or selenium phase in the ingots. EXPERIMENTAL PROCEDURE The starting materials used for the alloy preparations were 99.999 pct pure bismuth, antimony, and tellurium and 99.997 pct pure selenium. The bismuth and antimony were obtained from Consolidated Mining and Smelting Co. of Canada Ltd., while the selenium and tellurium were obtained from Canadian Copper Refiners Ltd. The tellurium was purified further in the laboratory by zone refining. The elements were pulverized in a stainless-steel pestle and mortar. The amounts for the desired composition were weighed out each time on an analytical balance to make up a 100-g sample. Then the sample was introduced into a Vycor ampule (19 by 150 mm), pumped down to a vacuum of 10"5 Torr for 15 min, and sealed off. The ampule was then heated in a horizontal resistance furnace at 800" to 900°C for about 20 hr. During this period the assembly was rocked back and forth several times to ensure good mixing. At the end of the heating period, the ampule was quenched in cold water and then transferred to the zone-melting apparatus described in a previous publications to grow large-size aligned polycrystals. The background and ring-heater temperatures were adjusted to make the freezing solid-liquid interface slightly convex to the liquid. The recorded temperature gradient in the vicinity of the freezing solid-liquid interface was around 15°C per cm. The ampule was moved horizontally at a speed varying from 0.4 to 2 cm per hr so that the ring heater would cover the whole ingot length from end to end. A single zone-melting pass was used for the Bi-Te, Sb-Te, and Bi-Sb-Te ingots. Two passes in the forward and reverse directions were carried out for the Bi-Se and Bi-Se-Te ingots. Six passes in the forward and reverse directions were performed for the Bi-Sb-Se-Te ingot. The zone-melted ingots were found to contain several large crystals, with their basal planes (0001) approximately parallel to the growth axis. Samples of bismuth and antimony tellurides coated with a layer of tellurium, and bismuth selenide coated with a layer of selenium, were prepared for comparison in phase identification. These coatings were made by dropping a piece of the zone-melted ingot into some molten tellurium or selenium under argon atmosphere and allowing them to cool slowly to room temperature. The metallographic specimens were prepared by

Jan 1, 1969

By Charles S. Barrett

This paper is a progress report covering metallographic applications of the electron microscope that have been made during the past year at Carnegie Institute of Technology. An account is presented of the techniques that have been most satisfactory, the difficulties encountered, the resolution obtained, and the peculiarities that have been noted in the microstruc-tures. About 1200 exposures have been made during the year on the instrument, which is an RCA type B2 transmission microscope,' and a number of these have been selected to illustrate the results obtained. prints are also included showing the common types of falsities—to borrow a term from the biological field, the "artifacts." ln brief, the paper is a record of our attempt to determine the value of the electron microscope in the study of the structure of metals and alloys. In addition to comments on techniques and the quality of photomicrographs obtainable with them, the paper discusses the nature of the etch attack on a few metals, and the possible relation between the fine structure revealed by etching and the mosaic block structure of the grains, since numerous papers and reviews are available on the subject of imperfection in crystals, the comments here may be very brief; in fact, are restricted almost entirely to points having to do with recent theories relating the strength of metals to imperfections and to spacings of slip lines. Specimen Preparation and Photographs Mechanical polishing by hand was used throughout this work. Precautions that must be taken in microscopy at high magnification, which have been well explained by Vilella in his book on Metallographic Technique for Steel, are likewise important with the electron microscope. This applies particularly to the need for these polishing and etching (each successive polish becoming less severe and each etch lighter), since the fina1 etch should in general be no heavier than is used for oil-immersion optical microscopy and in many instances should be much lighter (compare Figs. 6a and 7a, 6d and 7b). An extremely light etch, of course, is incapable of cutting through a flowed layer of appreciable thickness. Unquestionably it would be very advantageous in each instance to compare the structures obtained by electrolytic polishing with those obtained by mechanical polishing, but difficulties with the electrolytic method have prevented this in the following collection of prints. The choice of etchant is important, of course; for example, picral proved superior to nital for tempered martensite. With the exception of Figs. Ib and 16, the replicas used were of silica, deposited upon polystyrene and floated from the polystyrene in ethyl bromide according to the method of Heidenreich and Peck.2 The samples were mounted in Bakelite, polished and etched, then the polished Bakelite

Jan 1, 1944

By Charles S. Barrett

This paper is a progress report covering metallographic applications of the electron microscope that have been made during the past year at Carnegie Institute of Technology. An account is presented of the techniques that have been most satisfactory, the difficulties encountered, the resolution obtained, and the peculiarities that have been noted in the microstruc-tures. About 1200 exposures have been made during the year on the instrument, which is an RCA type B2 transmission microscope,' and a number of these have been selected to illustrate the results obtained. prints are also included showing the common types of falsities—to borrow a term from the biological field, the "artifacts." ln brief, the paper is a record of our attempt to determine the value of the electron microscope in the study of the structure of metals and alloys. In addition to comments on techniques and the quality of photomicrographs obtainable with them, the paper discusses the nature of the etch attack on a few metals, and the possible relation between the fine structure revealed by etching and the mosaic block structure of the grains, since numerous papers and reviews are available on the subject of imperfection in crystals, the comments here may be very brief; in fact, are restricted almost entirely to points having to do with recent theories relating the strength of metals to imperfections and to spacings of slip lines. Specimen Preparation and Photographs Mechanical polishing by hand was used throughout this work. Precautions that must be taken in microscopy at high magnification, which have been well explained by Vilella in his book on Metallographic Technique for Steel, are likewise important with the electron microscope. This applies particularly to the need for these polishing and etching (each successive polish becoming less severe and each etch lighter), since the fina1 etch should in general be no heavier than is used for oil-immersion optical microscopy and in many instances should be much lighter (compare Figs. 6a and 7a, 6d and 7b). An extremely light etch, of course, is incapable of cutting through a flowed layer of appreciable thickness. Unquestionably it would be very advantageous in each instance to compare the structures obtained by electrolytic polishing with those obtained by mechanical polishing, but difficulties with the electrolytic method have prevented this in the following collection of prints. The choice of etchant is important, of course; for example, picral proved superior to nital for tempered martensite. With the exception of Figs. Ib and 16, the replicas used were of silica, deposited upon polystyrene and floated from the polystyrene in ethyl bromide according to the method of Heidenreich and Peck.2 The samples were mounted in Bakelite, polished and etched, then the polished Bakelite

Jan 1, 1944

By H. E. Searle, Robert J. McKay, O. B. J. Fraser

The practical study of corrosion requires consideration of its economic aspects. It must be based on sound scientific principles, but it should be borne in mind that probably the most important object of a corrosion test is to determine what metal in corrosion-resisting construction will produce the greatest operating profit. Thus the corrosion test must be directly connected with money values or it is not a practical corrosion test. This, perhaps unusual, connection between corrosion and economics is partially due to the fact that corrosion deals only with the time factor or duration of equipment, and it is almost the only test which deals with this feature. In these statements a departure is made from the academic definition of the word corrosion and it is done deliberately. The use of the term corrosion is unusual. It is as though we spoke of a tensile test as a "breaking" test. We are not interested primarily in the break but in the strength of the metal. There is no English word which expresses our main interest in corrosion-testing, but let us have clearly in mind that we make corrosion tests to prevent corrosion. Our real interest is in this corrosion-prevention, not in the corrosion. Previous to 1922, it was common comment that "it is impossible to determine the course of corrosion by laboratory testing.'' This statement was true at that time in that the technique of laboratory testing for corrosion resistance was so vague that tests in the laboratory gave untrue results almost as often as true ones. This was so, even in the simple case of determining which one of two metals better resists a given solution. While this is no longer true the number of misleading "corrosion tests" still being ground out by laboratories is too large in the light of our present knowledge. There are two important features of corrosion testing whose neglect is a large contributing factor to misleading results: (1) The economic relations of the corrosion tests to other tests; (2) testing technique. Regarding economic relations J. F. Thompson l has said: "The use of any particular metal is rarely based upon the sole property of resistance to corrosion. In fact, I should like to venture the assertion

Jan 1, 1929

By Robert J. McKay, O. B. J. Fraser, H. E. Searle

The practical study of corrosion requires consideration of its economic aspects. It must be based on sound scientific principles, but it should be borne in mind that probably the most important object of a corrosion test is to determine what metal in corrosion-resisting construction will produce the greatest operating profit. Thus the corrosion test must be directly connected with money values or it is not a practical corrosion test. This, perhaps unusual, connection between corrosion and economics is partially due to the fact that corrosion deals only with the time factor or duration of equipment, and it is almost the only test which deals with this feature. In these statements a departure is made from the academic definition of the word corrosion and it is done deliberately. The use of the term corrosion is unusual. It is as though we spoke of a tensile test as a "breaking" test. We are not interested primarily in the break but in the strength of the metal. There is no English word which expresses our main interest in corrosion-testing, but let us have clearly in mind that we make corrosion tests to prevent corrosion. Our real interest is in this corrosion-prevention, not in the corrosion. Previous to 1922, it was common comment that "it is impossible to determine the course of corrosion by laboratory testing.'' This statement was true at that time in that the technique of laboratory testing for corrosion resistance was so vague that tests in the laboratory gave untrue results almost as often as true ones. This was so, even in the simple case of determining which one of two metals better resists a given solution. While this is no longer true the number of misleading "corrosion tests" still being ground out by laboratories is too large in the light of our present knowledge. There are two important features of corrosion testing whose neglect is a large contributing factor to misleading results: (1) The economic relations of the corrosion tests to other tests; (2) testing technique. Regarding economic relations J. F. Thompson l has said: "The use of any particular metal is rarely based upon the sole property of resistance to corrosion. In fact, I should like to venture the assertion

Jan 1, 1929

By Kenneth B. Ray, George R. Gardner

The application of wet cleaning processes for the beneficiation of bituminous coal has created in some localities a problem in the recovery and disposal of fine solids in the washery water. The maximum allowable concentration of these solids in the washery circuit that is consistent with satisfactory operation of the cleaning units remains a controversial point. It has, however, been generally recognized for a number of years that some degree of control should be exerted over the concentration of such material. Early methods of control involved intermittent or continuous discharge of a portion of the plant slurry into near-by streams or settling ponds, and this persisted even after the adoption of settling tanks or cones. The practice is not always economical, for two reasons: first, because of the waste of coal, and, second, because it is sometimes difficult and expensive to obtain an adequate supply of water. The latter condition often is aggravated by chemical treatment of the make-up water that is necessary to prevent excessive corrosion of plant equipment. The modern approach to this problem has been the adoption of continuous thickening devices. However, because such equipment occupies considerable plant space and is somewhat expensive to construct, the practice of loading these thickeners beyond their rated capacity is widespread, therefore often the performance of such units is not altogether satisfactory. In recent years, European washeries have increased the rate of settling of the fine coal from the slurry by the addition of specially prepared starch solutions. These reagents cause flocculation of the solid particles and thereby increase the rate of sedimentation. The first important work on the flocculation and clarification of coal slurry was done by Henry, who developed the Henry process and used it successfully in Belgian preparation plants. Soon after the initiation in Belgium, the process was introduced into England, where subsequent investigation developed similar processes, which were successfully used in

Jan 1, 1940

By J. H. Hollomon, L. D. Jaffe

The hardenability concept has become widely used during the last few years for the choice and substitution of steels. Before the work of Grossmann,1 the systems for predicting hardenability from chemical composition could be used only over a narrow range of composition. Grossmann introduced a comprehensive system, which has been effective in calculating the hardenability of most types of moderate or low-alloy steels. However, occasions often arise that require the calculation of the hardenability of high-alloy steels from their chemical compositions. Experimental determinations of the hardenabilities of such steels indicate that the Grossmann system predicts much greater hardenabilities than are realized. The fact that cases do arise in which the Grossmann method does not apply indicates that the fundamental hypothesis of the system may not be generally applicable. It seems advisable to re-examine not only Grossmann's system but also the concept of hardenability itself. Hardenability If steel parts are to possess a martensitic structure after quenching, they must first be austenitized and then cooled through the pearlite and bainite transformation ranges sufficiently rapidly to avoid the formation of pearlite, bainite, and pro-eutectoid products.* If, on cooling, these transformations are avoided, the resulting structure can consist only of martensite (and retained austenite). The hardenability of a steel is measured in terms of the severity of the cooling conditions necessary to avoid the pearlite and bainite transformations. The less rapid is the cooling necessary to prevent the formation of bainite and pearlite, the higher is the hardenability. The pearlite and bainite reactions appear to be differently affected by the alloying elements. Not only is this indicated by the published isothermal transformation data, but recent work by Zener2 affords a rational interpretation of the differing effects of the alloying elements. Manganese,3 for example, appears to decrease the rates of the pearlite and bainite transformations by equal percentages, while molybdenum45 is approximately 10,000 times more effective in retarding the pearlite than in retarding the bainite transformation, on the basis of isothermal measurements. In some steels, the formation of bainite restricts the formation of martensite while

Jan 1, 1947

By L. D. Jaffe, J. H. Hollomon

The hardenability concept has become widely used during the last few years for the choice and substitution of steels. Before the work of Grossmann,1 the systems for predicting hardenability from chemical composition could be used only over a narrow range of composition. Grossmann introduced a comprehensive system, which has been effective in calculating the hardenability of most types of moderate or low-alloy steels. However, occasions often arise that require the calculation of the hardenability of high-alloy steels from their chemical compositions. Experimental determinations of the hardenabilities of such steels indicate that the Grossmann system predicts much greater hardenabilities than are realized. The fact that cases do arise in which the Grossmann method does not apply indicates that the fundamental hypothesis of the system may not be generally applicable. It seems advisable to re-examine not only Grossmann's system but also the concept of hardenability itself. Hardenability If steel parts are to possess a martensitic structure after quenching, they must first be austenitized and then cooled through the pearlite and bainite transformation ranges sufficiently rapidly to avoid the formation of pearlite, bainite, and pro-eutectoid products.* If, on cooling, these transformations are avoided, the resulting structure can consist only of martensite (and retained austenite). The hardenability of a steel is measured in terms of the severity of the cooling conditions necessary to avoid the pearlite and bainite transformations. The less rapid is the cooling necessary to prevent the formation of bainite and pearlite, the higher is the hardenability. The pearlite and bainite reactions appear to be differently affected by the alloying elements. Not only is this indicated by the published isothermal transformation data, but recent work by Zener2 affords a rational interpretation of the differing effects of the alloying elements. Manganese,3 for example, appears to decrease the rates of the pearlite and bainite transformations by equal percentages, while molybdenum45 is approximately 10,000 times more effective in retarding the pearlite than in retarding the bainite transformation, on the basis of isothermal measurements. In some steels, the formation of bainite restricts the formation of martensite while

Jan 1, 1947

By Ross Glanville

INTRODUCTION The Optimum Production Rate (OPR) is one of the most important parameters in the evaluation of a mineral deposit. The OPR can also be expressed as the Optimum Mine Life (OML) in years since the expected mine life is determined by dividing the OPR per year into the estimated ore reserves. Unfortunately, very little time and effort has been directed towards the determination of the OPR. Instead, "rules of thumb" are often applied to select a mine life without due consideration of the economic implications of such a selection. A "justification" for a particular production rate is often based on a pre-conceived arbitrary requirement for a mine life of 5, 10, or 15 years, for example. In this paper it is demonstrated that such arbitrary selections for high-grade/low-tonnage mines (such as many underground gold/silver deposits) often lead to sub-optimal results. In fact, an apparently uneconomic deposit at an arbitrary production rate may be economic at the OPR. Consequently, investment opportunities may be overlooked if one analyzes mine properties based on arbitrary production rates. This paper analyzes the interrelationships of variables such as production rates, capital and operating costs, cut-off grades, discount rates, metal prices, etc. The analysis shows that the OML for high-grade/low-tonnage deposits is often in the range of two to four years. Although such mine lives intuitively appear too short to many individuals, it should be noted that, in the past, much of the mining industry became familiar with the economics of large scale mining operations. The rules of thumb developed for such large scale operations should not be applied to high-grade/low-tonnage mines such as many of the underground gold deposits. DEFINITION OF OPTIMUM PRODUCTION RATE The OPR is selected on the basis of maximizing the net present value of the after-tax cash flows. However, as discussed later in this paper, the production rate selected for a particular mine may be somewhat higher or lower than the theoretical OPR as a result of other variables such as: 1) the probability or expectation of additional reserves being discovered 2) the likelihood of being able to custom mill nearby deposits owned by others 3) the configuration or attitude of the orebody, which may place upper limits on the production rate 4) the residual, or salvage values, of the mine/mill facilities COMPARISON BETWEEN DIFFERENT PRODUCTION RATES For an orebody with definite physical cutoffs*, or boundaries (such as faults or unconformities), the total ore reserves at different production rates may be identical. Consequently, for such an orebody, varying production rates result in differing mine lives. Although the metallurgical recoveries, the mine dilution, and other similar physical parameters may vary slightly at different production rates, the major differences are the capital costs and operating costs per ton. The ramifications of these differences are especially important at low production rates (up to approximately 1000 tons per day), but can also be significant at higher production rates.

Jan 1, 1985

By Roscoe C. Clark

A study of the effect of various corrosive waters on five different types of cements indicated that those cements containing less than 5 per cent tricalcium aluminate were the most resistant to corrosion. INTRODUCTION Oil field experience indicates that some formation waters are excessively corrosive to some cements. A study has been made to determine the most corrosive waters and the relative resistance of various types of cement to these corrosive waters. PROCEDURE This study of the corrosion of cement was limited to an evaluation of the effect of various corrosive waters on five different types of cements. A determination was made of the types of cements which offer the greatest resistance to corrosion and of the chemical contents of waters found to be the most destructive to cements. The laboratory tests were conducted by immersing small cylinders of 20 samples of set cement in various corrosive waters. The initial mixing of most of the cement slurries was done using Tulsa tap water as the mixing water; however, a few of the slurries were mixed using a sulfate water as the mixing water. When the 20 samples had been immersed for a period of nine months, they were removed from their corrosive baths, inspected and photographed. The field tests were conducted by placing ten cement specimens, each contained in a screen wire thimble, in the gas anchors of insert pumps in wells in six different fields. The specimens were observed whenever it was necessary to pull the pumps and were returned to the 1aboratory when deterioration had reached a serious state. EXPERIMENTAL RESULTS In both the field and laboratory tests the resistance of the different cements to corrosion was determined by the condition of the samples and the number of samples of each that were in good condition at the end of the immersion period. Table I lists the various cements tested in the order of their resistance to corrosion with the most resistant at the top and the least resistance at the bottom. An analysis of Table I reveals that the upper half of the table predominates in slow set and sulphate resisting cement.: (low 3CAO.A12O3 content) while in the lower half the port-land and high early strength cements are in the majority. Of the last two the high early strength cements appear to offer less resistance to sulfate water corrosion. An investigation of the composition of the cements listed in Table I indicated that as a general rule the cements containing less than five per cent tricalcium aluminate will exhibit the greatest resistance to corrosion. The destructive action of various corrosive waters was compared by listing the waters in the order of those containing the largest number of samples that failed completely. These ratings are presented in Table II with the most corrosive waters listed first and the least corrosive last. Figs. 1 and 2 show the end views of cement samples which had been immersed in the baths of five per cent MgSO, water and the five per cent Na2SO4 water respectively in the laboratory. These .pictures are representative of the results obtained and present a pictorial evaluation of the corrosive resistance of various types of cements.

Jan 1, 1950

By George R. Gardner, Kenneth B. Ray

The application of wet cleaning processes for the beneficiation of bituminous coal has created in some localities a problem in the recovery and disposal of fine solids in the washery water. The maximum allowable concentration of these solids in the washery circuit that is consistent with satisfactory operation of the cleaning units remains a controversial point. It has, however, been generally recognized for a number of years that some degree of control should be exerted over the concentration of such material. Early methods of control involved intermittent or continuous discharge of a portion of the plant slurry into near-by streams or settling ponds, and this persisted even after the adoption of settling tanks or cones. The practice is not always economical, for two reasons: first, because of the waste of coal, and, second, because it is sometimes difficult and expensive to obtain an adequate supply of water. The latter condition often is aggravated by chemical treatment of the make-up water that is necessary to prevent excessive corrosion of plant equipment. The modern approach to this problem has been the adoption of continuous thickening devices. However, because such equipment occupies considerable plant space and is somewhat expensive to construct, the practice of loading these thickeners beyond their rated capacity is widespread, therefore often the performance of such units is not altogether satisfactory. In recent years, European washeries have increased the rate of settling of the fine coal from the slurry by the addition of specially prepared starch solutions. These reagents cause flocculation of the solid particles and thereby increase the rate of sedimentation. The first important work on the flocculation and clarification of coal slurry was done by Henry, who developed the Henry process and used it successfully in Belgian preparation plants. Soon after the initiation in Belgium, the process was introduced into England, where subsequent investigation developed similar processes, which were successfully used in

Jan 1, 1940

By C. S. Blair

THE development of a geological department as an integral part of the Tennessee Coal, Iron & Railroad Co. in the Birmingham district, Ala-bama, in 1908 was an innovation probably unique for any mining organ-ization south of the Ohio River, At that time a few of the oil companies were starting geological departments, but there were no geologists among the larger industrial organizations. The Tennessee Coal, Iron & Railroad Co. had been a substantial producer of pig iron for many years and was just getting a start in the manufacture of steel products from the pig iron. It had large acreages of coal land, ore land and timber land, but there was lacking the detailed knowledge of the possible mineral resources of much (of its territory, and this territory at that time covered an area in the neighborhood of 500,000 acres in the states of Alabama, Tennessee and Georgia. Those responsible for the operations of the mining properties, not being familiar with the kind of help that might be expected from geologic work, were decidedly skeptical of the utility of the work. Therefore it was necessary to develop cooperation with the mining organization, by not infringing upon its functions, and by developing the work in such a manner as to demonstrate to the mining department its practical utility. In the first instance the man responsible for a mining operation is apt to assume the attitude that the geologist is a blockader, because the geologist, unfortunately, is obliged to point out difficulties in the carrying out of mining operations in the way originally planned. He points out the dangers of mining out one coal or metal seam at the ultimate expense of an upper or lower seam, and he develops structural features, such as faults and folds, which call to the attention of the mining operator diffi-culties in his future operations, which the latter had not anticipated. Eventually, however, -the value of having these data became ap to the Tennessee Coal, Iron and Railroad Co., and the operators not only welcomed the geological work and cooperated fully in its acquisition of essential information, but reached the point of asking assistance and advice; and complete coordination of the two activities has existed for many years.

Jan 1, 1933

By Jonathan S. Jackson, Bayne B. McMillan, W. Joseph Schlitt

Various dump leach models have been developed by Kennecott, and these are reviewed with an eye toward production forecasting. Some of the models have been bated on first principles, utilizing the chemistry and physics of dump leaching. While providing considerable insight into the leaching process, these have proved to be too cumbersome for use in estimating production. Other models have been based on a declining leach rate for a single block of waste. These permit good short-term projections of solution grades and production, but are inflexible with regard to changes in mining parameters because the trends are based only on historical data. Therefore, a simple and flexible computer model has been developed to aid in leach production forecasting and to provide a tool for assessing the impact of different mining plans on leaching. This program, LEACH, is based on annualized blocks of waste; input parameters are described and examples of its use are given.

Jan 1, 1980

By S. S. Clarke

THE opening of zinc-lead ore bodies in the lower chert beds of the Tri-State district, locally called sheet-ground deposits, [ ] presented several new economic operating problems to be solved before the low-grade deposits could be mined profitably. Drilling was the first high-cost problem and loading and haulage difficulties followed. At this time, the sheet-ground mines are producing about 2000 tons per day. GEOLOGY The geology and ore deposits of the Tri-State district have been covered in detail by [ ] Fowler and Lyden.* Briefly, the sheet-

Jan 1, 1942

By Bernard Moore

THE last few decades have witnessed the introduction of many new nonmetallic mineral products and changes in the use of many of those already well known. Among these is diatomite, formerly employed as a mild abrasive and, at one time, as the absorbent material in dynamite. Now nearly 100,000 tons a year are mined and milled into such things as filter aids, cement admixtures, insulants, fillers, absorbents, cosmetics, cleansers, etc. Pumice, commonly regarded as only an abrasive, is now also employed as an insulant, as light-weight aggregate and as a concrete admixture. With increasing use of insulants, light-weight aggregates, and acoustic stuccos and plasters in the building trades, both these mate-rials should find increased application. Very large deposits occur in eastern Oregon and have been studied by the U. S. Geological Survey in cooperation with the Oregon State Mining Board.

Jan 1, 1934

By Fred K. Stieler

The largest updraft sinter machine built has a roasting area of 132 sq.m. Sinter machines with an area of over 200 sq.m. are under consideration. These large machines require new techniques with regard to drive thrust and sealing mechanism. To optimize the results of sinter plants, the charge preparation systems and the return fines circuits were improved. Special crushers were developed for crushing return sinter of up to 800 ºC to a size of minus 6 mm. Strand cooling of Pb-sinter was investigated. Different methods for plant ventilation were compared. New processes, which might replace sintering in the future, are in the stage of large - scale testing.

Jan 1, 1977

By M. B. Holt

At this time, when electricity in its various applications is attract- ing so much interest, and with such good reason, it has been suggested to me that, as the Aspen Mining and Smelting Company, of Aspen, Pitkin county, Colorado, was the first mining company in America to employ electrical power for hoisting, a record of what has been accomplished by this company would be of interest. Early in the year 1888 the question of power for the development of the ore-horizon lying below the level of the tunnel through which the property is worked, became one of importance. The conditions under which it was proposed to use power were as follows (See Fig. 1): The company's mines lie upon the northwestern slope of a mountain, the ascent of which is at an angle of 28' from the horizon. The ore, consisting of argentiferous galena and other silver-bearing mineral, is found at or near the plane of contact of a superincumbent mass of blue limestone, with an underlying bed of dolomite. This contact plane dips north 30° west, at an angle of 60' with the horizon. A tunnel 1000 feet in length, driven south into the mountain near

Jan 1, 1892

By Y. Takahashi, I. Iwasaki, S. Tanabe

Supported by the vigorous capital investment of the heavy and chemical industries and by the ever-increasing demand for durable consumer goods in the past decade, Japan has now emerged as the world's third largest steel producer, surpassed only by the United States and the Soviet Union. In 1968, the crude steel production is expected to exceed 50 million tons; the per capita steel consumption at that time will reach 886 lb, approaching the level of Western Europe. Characteristics of the Japanese steel industry is the high dependence of raw materials on overseas sources. Before World War II the industry relied on North China and Manchuria for coking coal, and on middle China, Hainan Island, the Philippines and the Malayan Peninsula for iron ores. After the war, the major sources of iron ores were shifted to the Philippines and the Malayan Peninsula, supplemented by shipments from the United States, Canada, India and Goa. The United States, in addition, became the primary source of coking coal.

Jan 1, 1967

By F. A. Schaufelberger

Early work on chemical precipitation of metals from metal salt solutions is reviewed. The chemistry and thermodynamics of precipitating copper, nickel, cobalt, and cadmium metals by reaction with hydrogen are discussed. Mechanisms of metal precipitation, nu-cleation, growth, and agglomeration are reviewed, as well as some solubility phenomena of cleation,gases and solids at elevated temperatures. Experimental data presented deal mainly with the reaction of copper sulfate solution with Hz. METAL can be recovered from a leach solution either indirectly by precipitation as a compound that is later reduced or directly by electrolysis, cementation, or chemical reduction, for example, with hydrogen. The widely used electrowinning processes suffer from the inefficiency of converting fuel to low voltage dc and from low current efficiency when complete recovery is attempted. With the batch hydrogen reduction methods outlined here, a unit of fuel converted to hydrogen in modern gas reform plants will make two to three times as much metal as can be obtained with electrolysis. With continuous hydrogen reduction, four to six times as much metal is obtained. Precipitation by reducing a metal salt solution with H, has been known for almost 100 years.' Commercial use of the process, however, awaited the research and development program initiated by Chemical Construction Corp. Within the last few years this program has brought about construction of commercial plants, listed on p. 701. Ideal hydrogen reduction will precipitate a pure metal from a solution obtained by commercial leaching methods at a rapid rate without excessive temperatures and pressures. The metal precipitate will be of desired size and density, less than a percent left in the vessel being deposited on the wetted parts. The present discussion will outline Chemical Construction Corp.'s early development program and will discuss the chemistry and mechanics of reducing copper, nickel, cobalt, and cadmium from solution by H2. Work on selective reduction of nickel from cobalt has been described earlier.2 The article is not concerned with precipitation of copper by disproportionation of cuprous solutions where yield is limited" to 50 pet.* It does not discuss use of gaseous reducing agents other than hydrogen, such as SCV which may lead to contamination with sulfur, or CO," which is considerably more expensive than hydrogen and produces a gaseous reaction product, CO2.† The article does not include use of other nongaseous reducing agents: which are far more expensive than CO. Also, notes on the history, engineering design, and performance of commercial plants have been given elsewhere." It will be shown that a pure metal can be precipitated by reduction with hydrogen from solutions obtained by commercial leaching methods when the solution cohposition is controlled and proper acidity, proper metal ion concentration through controlled complex formation and hydrolysis, and adequate agitation for suspension of metal and for transfer of reducing gas are maintained. Reasonable temperatures and pressures are used which are less excessive than those used by previous workers, although they are maintained at above equilibrium values because of process kinetics.' It has also been found necessary to induce nuclea-tion and to control growth and agglomeration in order to get a powder product of suitable physical properties. Review of the Literature Muller, Schlecht, and Schubardt of I. G. Farbenm claimed a successive reduction of silver, copper, nickel, cobalt, and zinc from ammoniacal solution by applying progressively higher temperatures and hydrogen pressures. Metals produced by this technique were not pure, since no attempt was made to adjust the solution composition between the different reductions. It is doubtful that the zinc product contained any metallic zinc. The major contribution to the literature" was made by the Ipatiews,12 who prepared platinum, iridium, copper, nickel, cobalt, lead, tin, arsenic. antimony, and bismuth at often extreme conditions, up to the critical temperature of water (373"C), at 1500 to 7500 psi, for as long as several days. Even cadmium and zinc were claimed to have been observed in trace quantities precipitated together with basic salts. In the early experiments solutions were not stirred. Extensive formation of oxides and basic salts occurred. probably long before sufficient hydrogen could be supplied in the unstirred liquid to decrease the metal concentration in solution by reduction. The importance of hydrogen pressure was

Jan 1, 1957