Search Documents

By W. J. Carlson, I. lwasaki

Manganese and silica in nonmagnetic tailings from the direct reduction-magnetic separation step were so closely associated that no physical concentration methods were effective. Dilute sulfuric acid dissolved manganese and iron rapidly; manganese in the form of silicates was virtually insoluble in sulfuric acid solutions, thereby governing the maximum extraction attained by leaching. Autoclave leaching at elevated temperatures and at high oxygen pressures reduced the iron extraction to less than one tenth without affecting the manganese extraction. There was an indication that autoclaving solubilized the manganese silicates appreciably. Elimination of iron from leach solutions was carried out by aerating the solution in the pH range of 6.5-7; a platinum-calomel electrode pair provided a reliable indicator for the end point of iron removal. The purified leach solutions were free of interfering impurities for the recovery of manganese as metal, dioxide, or carbonate. Manganiferous iron ores of the Cuyuna Range, Minn., are too low in iron content to be directly useful as iron ores, and too low in manganese content to be termed manganese ores. Common methods of physical beneficiation such as gravity concentration and flotation have not been successful in upgrading this material. The R-N process, when applied to manganiferous iron ores,1'2 produces sponge iron by direct reduction of iron oxides, while leaving manganese as manganous oxide. From fine grinding and magnetic separation of the reduced ore, a tailing is produced which is relatively rich in manganese and low in iron content. The nonmagnetic tailing can readily be leached with acids and then further processed to recover manganese in various forms. In this way, two processes, neither of which would be an economic solution to the Cuyuna ore problem by itself, may be combined to produce two marketable products, thereby rendering the over-all process economically more attractive. This article reports on the results of a leaching study on the nonmagnetic tailings, both in a batch agitation vessel and in an autoclave; on the problems involved in the purification of leach liquors by aeration; and on the recovery techniques used to produce manganese metal by electrolysis, manganese dioxide either by electrolysis or by autoclaving, and

Jan 1, 1968

By L. J. Dijkstra, R. J. Sladek

IN earlier work the effect of manganese on the general behavior of nitrogen in iron was the subject of a careful examination by Fast.' Part of the investigation was made, in collaboration with one of the present authors (L.J.D.), by using the internal friction method. This technique, which has been described elsewhere,' showed some significant changes in the properties of Fe-N alloys by the addition of a small amount of manganese namely: 1—Under standard conditions the maximum of the nitrogen peak in pure iron appears around 20 °C and the half width is about 27 °C. By addition of 0.5 atomic pct Mn a general broadening of the internal friction peak occurs. The half width is increased by about 9°C. Moreover, a shift of the maximum of about 5°C toward a higher temperature takes place, Fig. 2. 2—The precipitation of nitrogen from the supersaturated solution, measured, e.g., at 200 °C, was inhibited by the addition of the amount of manganese given in effect 1. The broadening of the nitrogen peak was confirmed in more recent work3 on samples which were prepared from Westinghouse Puron iron. The effect of manganese on the rate of precipitation, however, was much less striking than in the earlier work' based on Philips high purity iron. Theory To explain the first change in properties just referred to, effect 1, the following two assumptions were made:' First, every manganese atom in sub-stitutional solid solution creates around it six interstices located between an iron and a manganese atom, as is evident from Fig. 1. These interstices, conveniently called Fe-Mn interstices, have for nitrogen a free energy level which is AG* lower than the normal Fe-Fe interstices between two iron atoms. For such low concentrations of manganese as 0.5 atomic pct, the possibility that two manganese atoms will be nearest neighbors can be disregarded. Second, it is assumed that in addition to the normal relaxation time TFe at least one new relaxation time, Mn, Fe, enters in the phenomena which is associated with the elementary diffusion jumps between a Fe-Mn interstice and an adjacent Fe-Fe interstice. Fig. 1 gives schematically the free energy for a nitrogen atom as a function of its position along the line ABC. A tentative analysis of the nitrogen peak in a 0.5 pct Fe-Mn alloy based on these assumptions has been made in Fig. 2. The dotted curve with a maximum at 22°C is caused by jumps between Fe-Fe interstices, the dotted curve with maximum at 32°C by jumps between an Fe-Mn and an Fe-Fe interstice. The two effects added together give the dash-dot internal friction curve for the alloy. In the following these two components will be referred to as the normal peak at 22°C and the abnormal one. (The small secondary peak at

Jan 1, 1954

By HARRISON W. CRAVER

THE principal purposes of library-catalogs are to enable a reader to find a book of which the author, the title, or the subject is known; to show what the library has. by a given author, or on a given subject; and to assist in the choice of a book, as to its edition, or as to its character. The author, in a narrow sense, is the person who writes a book; in a wider sense it is applied to him who is the cause of the book's existence, e.g., editor, translator, compiler, etc. Bodies of men, societies, and countries are, from a cataloging point of view, con¬sidered the authors of their official publications, memoirs, transactions, etc. All names selected as author names are arranged in strict alphabetical order. A subject catalog fulfills its purpose by entering or registering each book under the name of that subject or topic of which the book chiefly treats. It may or may not be alphabetical in arrangement. If the arrangement is not alphabetical, the catalog is commonly called a classed subject catalog, although this name might with equal propriety be applied to some alphabetical arrangements.

Jan 1, 1920

By Walter Miller

AFter a year's continued impact of war, the task of the petroleum-refining industry stands out clearly and looms up in larger aspect. This time it is not, as it was so largely in the first World War, simply a matter of increased quantity—more and more of the same petroleum products that had substantially been standard for years. In this era the emphasis is largely on newer and improved materials which had been produced, if at all, in comparatively insignificant quantities, and for which manufacturing equipment was not available on a large scale. At the beginning of 1942 four great product needs (besides a number of lesser ones) confronted the industry: 100-octane aviation gasoline, toluene for T.N.T. production, high-quality lubricating oils for aviation and Army equipment service, and petroleum chemicals for synthetic rubber manufacture. The difficulty in presenting a review of engineering progress in petroleum refining during 1942 is that there is so little one is free to say about so much which has been and is being accomplished. At the opening of 1942 the program was to increase the then existing capacity of 50,000 bbl. a day of aviation gasoline to over 150,000 bbl. daily by building new plants at an estimated installation cost of $150,000,000. Later in the year. after the announcement by President Roosevelt of a large increase in the program for war-plane building, additional contracts were made between the Reconstruction Finance Corporation and rehers to raise the capacity to 250,000 bbl. per day. The greatly increased scope of the war activities in all parts of the world, the obligation of the United States as the arsenal of the United Nations, and the greater importance and use of bomber, transport, and cargo planes will undoubtedly bring about plans and installations for a further increase in production of aviation gasoline over the present announced plan. In this connection, Jesse Jones, Reconstruction Finance Corporation Chairman, announced that as of Oct. 31 the R.F.C. had through its subsidiary Defense Plant Corporation entered into contracts for the construction, expansion, or equipping of 28 plants to increase 100-octane aviation gasoline production, but gave no data on 'capacity involved or completion dates. His list did not, of course, include a number of existing plants, and some installations being made by companies who are themselves financing the construction. Production from existing operating installations was materially increased in a number of instances as a result of pooling knowledge of improvements in operation and also by the exchange of Components going into 100-octane blend to enable greater quantities of aviation gasoline to be produced from the over-

Jan 1, 1943

By Walter Miller

AFter a year's continued impact of war, the task of the petroleum-refining industry stands out clearly and looms up in larger aspect. This time it is not, as it was so largely in the first World War, simply a matter of increased quantity—more and more of the same petroleum products that had substantially been standard for years. In this era the emphasis is largely on newer and improved materials which had been produced, if at all, in comparatively insignificant quantities, and for which manufacturing equipment was not available on a large scale. At the beginning of 1942 four great product needs (besides a number of lesser ones) confronted the industry: 100-octane aviation gasoline, toluene for T.N.T. production, high-quality lubricating oils for aviation and Army equipment service, and petroleum chemicals for synthetic rubber manufacture. The difficulty in presenting a review of engineering progress in petroleum refining during 1942 is that there is so little one is free to say about so much which has been and is being accomplished. At the opening of 1942 the program was to increase the then existing capacity of 50,000 bbl. a day of aviation gasoline to over 150,000 bbl. daily by building new plants at an estimated installation cost of $150,000,000. Later in the year. after the announcement by President Roosevelt of a large increase in the program for war-plane building, additional contracts were made between the Reconstruction Finance Corporation and rehers to raise the capacity to 250,000 bbl. per day. The greatly increased scope of the war activities in all parts of the world, the obligation of the United States as the arsenal of the United Nations, and the greater importance and use of bomber, transport, and cargo planes will undoubtedly bring about plans and installations for a further increase in production of aviation gasoline over the present announced plan. In this connection, Jesse Jones, Reconstruction Finance Corporation Chairman, announced that as of Oct. 31 the R.F.C. had through its subsidiary Defense Plant Corporation entered into contracts for the construction, expansion, or equipping of 28 plants to increase 100-octane aviation gasoline production, but gave no data on 'capacity involved or completion dates. His list did not, of course, include a number of existing plants, and some installations being made by companies who are themselves financing the construction. Production from existing operating installations was materially increased in a number of instances as a result of pooling knowledge of improvements in operation and also by the exchange of Components going into 100-octane blend to enable greater quantities of aviation gasoline to be produced from the over-

Jan 1, 1943

[Abstmct of remarks by R. II. Sweetser arid suhscqueut discussion at the New York Meeting, February, 1926. The Transactions mill ultimately contain a report of work resulting from these discussions. Need for a standard of ualuration.—There should be an accepted method for evaluating the different kinds of bituminous coals based on their carbon just as that for iron ores is based on iron. Variation in the classes of coals and their desirability fol the different industrial uses is analagous to the case of iron ores. The iron people have developed a standard. In the past coals have not been intelligently distributed because the public has not been informed as to its uses. Many operators have known nothing about the final disposal of the coal shipped from their mines. Sales agents and retailers have had no means of evaluating coals except to make the price as high as the market will stand. Producers and distributors need to know how much more valuable the coals would be if prepared so as to contain less objectionable material. Mr. Swectser cnlletl on the Goal and Coke Committee of the Institnte to organize a study through producers and users to develop a method scientifically and comnereially sound E. A holbrook said that the information exists but the public is unwilling to investigate. He praised Ashley's1 nomenclature of the different kind of coal which has been accepted by the Coal Mining Institute of America and recommended to the American Enginecring Standards Commitee. G. S. Rice pointed out the wider variety and distribution of consumption of coal compared to Iron ore. C'. M. Young approved Mr. Sweetser's remarks and hoped lor a research institution, probably endowed, to study utilization of coal after it comes from the ground. Mr. Sweetser cited incidents to prove his former statements. He said that a reduction of 1 per cent. ash in the coal would cut down the cost of pig iron at a blast furnace 30 c. a ton, that the coal men should tell what the iron men would have to pay to get better coal. H. J. Prryn endorsed the need of blast-furnace operators to know the kind of coal from which their- coke is made and the latler's ash content, as this affects coke consumption. A. C. Fieldncr explained that the difficulty of evaluating coal on the basis of chermical analyses for calorimetric tests is: (1) representativr

Jan 1, 1927

By Nelson Severinghaus

Following the end of hostilities of World War 11, a resurgence of industrial and home building has given impetus to the use of many products of the stone industry. Shortage and high prices of some building materials such as lumber have aided wider acceptance of materials such as concrete products which have been relatively plentiful and which have not risen so rapidly in price. Ingredients for many of these substituting materials come from the stone industries, often from by-products of stone operations. Most of the tonnage of the stone industry in the State of Georgia comes from granite and marble. There are extensive dimension stone operations in granite in the Elberton and in the Lithonia areas. Building and monumental marble from the Tate area has been used throughout the country. Cutting operations in both types of stone have their by-products in faulty blocks and in spalls. In the State there are three large crushed-stone plants utilizing granite, One near Camak, One near Lithonia and one at Stockbridge. All have had excess fines Or in in the past but this excess is largely disappearing with development of new uses. At times this "waste" has amounted to as much as 20 pct of the stone quarried. Handling Of this large tonnage from point of screening out to storage piles presented a costly problem and large areas were taken up by the piles. Crushed 'tone is generally sold with a a narrow margin Of price over cost, so any elimination of disposal cost or increase of income by marketing of by-products is highly desirable. By-products of Granite Dimension Stone It sometimes becomes difficult to differentiate between main product and byproduct. In the cutting of granite dimension stone in the Lithonia district of Georgia, a considerable quantity of remnants of Uneven shape and size is produced. The larger of these pieces have long found use as building rubble, particularly for retaining walls and building foundations (Fig I), They are broken down to one man size by plug drilling and wedging and by hammer. In recent times, demand for this former by-product has grown so that quarries have been opened for the production of rubble as a main product. Local masons have attained skill in using these irregular shapes to form economical and attractive walls. Areas such as Elberton, Georgia, which do not have a large building market nearby, tend to accumulate piles of large pieces of reject stone. When a road job or other local construction offers a quantity market for crushed stone, a portable crusher works this material down to crushed aggregate. Spalls and finer chips from granite stone-cutting operations have generally found their way into crushers and thence to the many uses for crushed aggregate. One company near Lithonia started marketing the smaller by-product crushed sizes for chicken grit about ten years ago. This use has grown to nation-wide distribution and the tonnage is now so great that they have opened a large quarry with

Jan 1, 1948

By Nelson Severinghaus

Following the end of hostilities of World War 11, a resurgence of industrial and home building has given impetus to the use of many products of the stone industry. Shortage and high prices of some building materials such as lumber have aided wider acceptance of materials such as concrete products which have been relatively plentiful and which have not risen so rapidly in price. Ingredients for many of these substituting materials come from the stone industries, often from by-products of stone operations. Most of the tonnage of the stone industry in the State of Georgia comes from granite and marble. There are extensive dimension stone operations in granite in the Elberton and in the Lithonia areas. Building and monumental marble from the Tate area has been used throughout the country. Cutting operations in both types of stone have their by-products in faulty blocks and in spalls. In the State there are three large crushed-stone plants utilizing granite, One near Camak, One near Lithonia and one at Stockbridge. All have had excess fines Or in in the past but this excess is largely disappearing with development of new uses. At times this "waste" has amounted to as much as 20 pct of the stone quarried. Handling Of this large tonnage from point of screening out to storage piles presented a costly problem and large areas were taken up by the piles. Crushed 'tone is generally sold with a a narrow margin Of price over cost, so any elimination of disposal cost or increase of income by marketing of by-products is highly desirable. By-products of Granite Dimension Stone It sometimes becomes difficult to differentiate between main product and byproduct. In the cutting of granite dimension stone in the Lithonia district of Georgia, a considerable quantity of remnants of Uneven shape and size is produced. The larger of these pieces have long found use as building rubble, particularly for retaining walls and building foundations (Fig I), They are broken down to one man size by plug drilling and wedging and by hammer. In recent times, demand for this former by-product has grown so that quarries have been opened for the production of rubble as a main product. Local masons have attained skill in using these irregular shapes to form economical and attractive walls. Areas such as Elberton, Georgia, which do not have a large building market nearby, tend to accumulate piles of large pieces of reject stone. When a road job or other local construction offers a quantity market for crushed stone, a portable crusher works this material down to crushed aggregate. Spalls and finer chips from granite stone-cutting operations have generally found their way into crushers and thence to the many uses for crushed aggregate. One company near Lithonia started marketing the smaller by-product crushed sizes for chicken grit about ten years ago. This use has grown to nation-wide distribution and the tonnage is now so great that they have opened a large quarry with

Jan 1, 1948

By C. D. Thompson, D. C. Violetta, C. A. Czako

The mechanics of the continuous sintering process are briefly reviewed and the application of this process for the beneficiation of principal minerals used in making cement is shown. Pilot plant tests using pyrobeneficiation techniques were conducted with mixtures of limestone and shale in various ratios. Results are illustrated and show the percentage removal of carbon, carbonates, sulfur, alkalies, and volatiles as a function of the limestone-shale ratio. Tests with varying quantities of solid fwls, added to mixtures containing limestone and shale in a 4 to 1 ratio, were made to attain optimum elimination of the volatile constituents. Experimental results show that 90 pct of these constituents were removed during the calcination sintem'ng process. The advantages of using the beneficiated material for making cement are discussed with regard to prepam'ng, handling, and clinkering operations. A sintering process for treating raw materials or kiln waste products which contain high amounts of alkaline materials is described. Tests were performed with a high alkaline waste dust mixed in a 1 to 1 ratio with raw cement meal. The data from these tests and others using different halides for aiding alkali removal are evaluated by the alkali content of the cement clinker. Test results showed that the Dwight-Lloyd process could be applied with facility in beneficiating raw materials for cement making. Substantial quantities of deleterious volutile constituents were removed by calcining and sintering techniques. The continuous sintering process has been applied for a number of years as a means of beneficiating minerals for subsequent conversion to merchantable products. The process was developed and first used for nonferrous metallurgical applicatfons. However, it has risen to prominence for ferrous metallurgical applications where last year in the U.S. and Canada nearly 40 million tons of iron ore were treated by grate firing processes. Through the years of process development many investigators have realized the versatility of the sintering process and have directed experiments toward the use of it for applications with nonmetallic minerals. These have included calcining limestone, carbonizing coal, expanding shale, and burning cement raw meal. Today commercial sintering plants produce cement clinker from mixtures of limestone and shale, lightweight aggregate from shale or clay, and calcined products from phosphate shale. The mechanics of the downdraft sintering process have been presented by many authors. In general practice the materials to be agglomated are mixed as moistened fines with a solid fuel and this mixture is spread uniformly on the grates of the sintering machine. The charge is then momentarily directed under an ignition furnace. After ignition a continuous downdraft of air promotes combustion of the fuel and through heat transfer particles become partially fused into a coherent mass. This is cooled from continued draft induced after combustion. Many investigators have shown that distinct zones are formed during the process of sintering iron ores. At the midway point of the sintering process these are prominent and are, respectively, from the top of the bed to the bottom, comprised of a cooling zone of sintered material, a combustion zone of sinter formation, a calcination zone, a drying zone, and a zone of unreacted materials. Completion of sintering occurs near the discharge end of the machine where the firing zone approaches either the grates or grate dressing material called hearth layer. Here the peak draft temperature usually can be noted in the windboxes. The zonal pattern has been illustrated with the use of graphs which show thermal gradients as they progress through the bed of materials during sintering. Fig. 1 shows, in simplified form, thermal gradients existing when clinkering cement on a sintering machine. The thermal gradients illustrated are for periods of initiation, midway and completion of the clinkering process. The occurrence of these zones has importance for the beneficiation of cement raw materials. A research program was performed at the Dwight-

Jan 1, 1961

By W. C. Ellis, E. S. Greiner, M. E. Fine

Discontinuous changes of Young's modulus, internal friction, coefficient of expansion, electrical resistivity, and thermoelectric power are evidence for a transition in chromium near 37OC. Although the X-ray diffraction pattern gives no clue, a difference between the thermal expansivity and the temperature dependence of the lattice parameter suggests a crystal-lographic change. Young's modulus data disclosed another transition near THE thermal dependence of a number of proper- ties of chromium indicates a transition occurring over a temperature range near room temperature. Bridgman' noted this first from a minimum in the electrical resistivity near 12°C. In a sample of greater purity, Sochtig' observed the minimum at 41 °C. Erfling3 reported an inflection in the thermal expansivity curve at 36°C. These temperature-dependence curves are reversible with no hysteresis being detected. No discontinuity or inflection has been observed in the heat capacity' or the paramagnetic susceptibility.' Likewise, no one has noted a change in crystal symmetry. In the present investigation Young's modulus, internal friction, coefficient of expansion, electrical resistivity, illustrated in Fig. 1, lattice constant, Fig. 2, thermal electromotive force, Fig. 3, and paramagnetic susceptibility, Fig. 4, were measured over an extended temperature range. The samples were prepared in two ways: (1) By cold pressing a sintered electrolytic powder compact,' and (2) by electroforming from an aqueous solution. The electroformed samples were prepared by R. A. Ehrhardt and G. Bittrich by plating on copper or nickel tubes from an aqueous solution according to the method of Brenner, Burkhead, and Jennings.' The pressed powder samples (method 1) were finally annealed at 1400°C in purified helium: the electroformed samples, packed in powdered chromium, were vacuum-annealed at 1000°C. From the composition of the original powder' the purity of the pressed powder samples is estimated to be 99.8 pct Cr. Spectrochemical analysis furnished by E. K. Jaycox, revealed only slight traces of impurities in the electroformed sample (less than 0.001 pct), neither iron nor nickel being detected. Chromium deposited by this method is reported to contain approximately 0.05 pct 0.- Methods and Data Young's Modulus: For measurement of Young's modulus, an annealed, pressed powder sample, 0.114 x0.237x1.845 in., and an electroformed sample, 0.10 in. od, 0.01 in. id, and 1.86 in. long, were prepared. The resonant frequencies of the rod samples in forced longitudinal vibration were measured at a series of temperatures from —192" to 200°C by a method previously de~cribed.6,7 Because the samples were nonferromagnetic, iron- silicon or molybdenum permalloy tips (0.013 in. thick) were soldered to the ends. The softening temperature of the solder limited the temperature of measurement. Young's modulus, E,, of chromium at temperature, T, may be calculated from the resonant frequency of the composite rod, f,; the thickness of the tips, t; the length of the chromium sample at 25°C, l,.; the density of chromium at 25°C, pc (7.20 g per cc);5 and the thermal expansivity, Al/l25. Modulus differences for two temperatures, ET and E, are accurate to +0.002x10" dynes per cm2. ET = 4PAlc+2tyf Young's modulus at 25°C, Fig. la, is 28.2~10" dynes per cm' (40.8xlO" si) in wrought chromium (upper curve). The modulus of the electroformed sample is apparently lower due to cracks. From the modulus measurements two transitions were observed: one with a critical temperature at 37°C, the other at —152°C. Internal Friction: The internal friction, 1/Q, was determined from the width, Af, of the strain amplitude-frequency curve at 0.707 times the strain amplitude at resonance;' the internal friction, 1/Q, then equals Af/f. Fig. lb shows a sharp peak in internal friction at 38°C. The internal friction of the electroformed sample had a similar maximum. Thermal Expansion: The expansivity measurements, shown in Fig. 2, covering the temperature range —195" to +400°C were made by D. MacNair in an interferometric dilatometer8 sing a sample consisting of three pyramids 0.25 in. high prepared from wrought electrolytic chromium. Below —120°C the experimental points deviated up to ±2x10 from the drawn expansivity curve in Fig. 2 because of decreased precision of the quartz wedge thermometer at low temperatures. Near 38°C the thermal expansivity curve, Fig. 2, goes through an inflection corresponding to a minimum in the coefficient of expansion, Fig. ld, and a relative volume decrease on heating. Electrical Resistivity: The variation of electrical resistivity with temperature measured by the po-tentiometric method is also shown in Fig. l. The resistivity of the wrought chromium (upper curve) at 20°C is 13.6 microhm-cm; of electroformed chromium (lower curve) 12.8 microhm-cm. The lower value reflects higher purity and agrees closely with a published value." A minimum at 40°C occurs in the resistivity curves of both samples. No conclusive evidence for a transition near — 150°C was observed, but the points, Fig. 1, appear to deviate from a smooth curve between —120" and —160°C.

Jan 1, 1952

By R. S. Hooper

IN attempting to describe recent mining developments at the Bunker Hill mine, it may be well to recall first the old days of hand mining when holes were laboriously drilled by hand to a maximum depth of three feet, and were shot one or two at a time, in order that the miner could take advantage of every slip, crack or bedding plane, and so save as much drilling as possible. Broken muck, of course, was loaded by hand shoveling into wheelbarrows or small cars, and heading advances or stope ton¬nages were governed by the number of men that could find room to work in any given place. The first big improvement over these old methods was the introduction of the reciprocating type of air-powered rock drill. This innovation, crude as it was, enabled the miners to set up a machine and drill a complete round of holes in one shift; but broken muck was still loaded by hand, and the size and rate of advance in headings were limited by time required to remove the broken rock. The next improvement of consequence was the appearance of the hammer-type rock drill, which greatly increased drilling speed over the reciprocating type, and made possible the completion of a full cycle in one shift, by the use of crossbars in headings, and permitted drilling and mucking to be carried on at the same time. Rock drills continued to improve as time passed, and finally the smaller and more efficient mucking machines appeared on the scene, and it became possible to muck out a round of broken rock and have a clean setup for one or more drill columns and machines. A complete cycle of mucking, drilling, and blasting was completed in one shift with an average advance of five feet. These conditions prevailed for several years, but as the mine grew deeper, the distances to transport the workers grew longer, and this fact together with the shortening of the working day, soon presented the problem of attempting to complete a cycle of operations in a shift of only six hours at the working faces. Anticipating this condition, the operating heads at the Bunker Hill had started an intensive study of more and better mechanization, and over a period of comparatively few years have adopted and placed in service methods and machines that make it possible for a three-man crew to consistently advance headings seven by nine feet in cross section, at the rate of eight feet, and more, per shift, doing all the mucking, switching, drilling and loading. These improvements consist of the following major items: I. The development of a light, flexible, easily transported jumbo equipped with pneumatic columns (Fig I), that has decreased the "setting up" and "tearing down" time an average of 1 1/2 hr per shift, or 25 pct of the available working time. These jumbos were developed at the Bunker Hill mine by members of the staff and consist of two pneumatic columns attached to a suitable carriage. They fold

Jan 1, 1947

By C. G. Durdaller, W. H. Robinson, G. M. Pound

The nucleation rate of the a (pay) to 0 (white) tin transformation was measured as a function of temperature and a tin particle size using an X-ray diffraction technique. The powder specimens of a tin were essentially monodisperse and the small dinzension of the particles of these specimens was varied from 13 to 75 p. Several types of nucleation sites of differing potency were fbund to be operative in the nucleation process, but it could not be determined whether these sites were on the free surface of the tin particles or within the volume. Assuming that they were on the free surface, the average density of the most potent sites was calculated to be 2.5 to 5.3 x 10' sites per sq cnz through the application of a Poisson distribztion finction to the isothermal data. Analysis of the temperature dependence' of the rate constmts at a given fraction transformed suggests that the active sites are regions of higher free energy and not catalytic interfaces. Appreciable induction periods were observed at the lower temperatures of transformation. Experimental studies1 of solid-solid phase transformations have led to the belief that the new phase nucleates at structural imperfections. The purpose of the present work was to learn more about the mechanism of nucleation in solids and the nature of the singularities at which nucleation occurs. In this investigation nucleation rates in the isothermal transformation of gray to white tin were measured by an X-ray diffraction technique using essentially monodisperse powders of gray tin. This particular phase transformation was chosen for study because it presented fewer experimental difficulties than most others. The experimental temperature-control problems were minimal because the two phases coexist in equilibrium at 13.3"C, and measurable transformation rates occur at temperatures only slightly above room temperature. The growth rate of the P phase into the a2 is sufficiently fast to make the measured transformation rate equivalent to the nucleation rate, provided that the particle size of the samples is small enough; for the experimental temperatures used in this study, the particle diameter must be less than 100 p. EXPERIMENTAL TECHNIQUE The P tin used in this study was obtained from Capper Pass and Son Ltd., North Ferriby, Yorkshire, England, and was of 99.999 pct purity. It was transformedS to the a phase and ground into a fine powder in an agate mortar. This powder was separated by a Roller air classifier into seven fractions whose dimensions, as determined by microscopic measurement of many thousands of particles, are given in Table I and whose distribution of size within each fraction is given in Figs. 1 and 2. The shape of the particles was roughly that of an oblate spheroid,

Jan 1, 1964

By T. L. CONDRON

DURING the past fourteen months, this committee has had under consideration and study the subject of the licensing or registration of engineers. The fifteen members of the committee as appointed by Council, were selected from thirteen states, viz., Connecticut, New York, Pennsylvania, Ohio, Georgia, Louisiana, Illinois, Missouri, Iowa, Minnesota, Colorado, California and Washington, and therefore represent practically all sections* of the United States, as well as mechanical, electrical, mining, hydraulic, municipal, sanitary, railway and' structural engineering, and also colleges of engineering. The first work of the committee was to investigate the general subject and to collect, so far as possible, avail¬able material bearing upon the subject in hand,. in-' eluding opinions from many engineers as to the need or desirability of legislation, as well as copies of all state laws passed and proposed, having to do with licensing or registration of engineers, architects and surveyor, This preliminary investigation disclosed that very pronounced views were held by engineers throughout the country, both for and against state licensing or registration. The general sentiment one year ago was more opposed to such measures than it is today. The older members of the profession did not as a rule favor licensing nor did they feel there was need for state regulation of engineering practice, while among the younger men there was a feeling that licensing or registration by the states would add prestige to professional engineers and in many ways benefit -the profession, as well as individual engineers.

Jan 1, 1920

By Clyde E. Williams

MUCH has been said recently concerning the depletion of the Lake Superior iron ore re- serves. Estimates given indicate a total life of the present known reserves of twenty to thirty years. Some argue that there is no need to concern ourselves about the possible depletion of the Lake Superior iron ore supply because foreign ores can be brought in to this country at a lower price than rich agglomerated ore can be produced from the lean domestic ores. Some fear, as a result of this, a displacement of the steel business from present districts to the Atlantic seaboard. Others show that foreign ores will be brought to interior points via the projected Great Lakes-St. Lawrence waterway. Others believe that the South, given better freight rates, will extend its iron and steel market into northern territory.

Jan 1, 1931

By Richard E. Chism

Some years ago, when I was seeking an illusive fortune and gaining a precarious existence in the primeval forests of Brazil, there penetrated, even to my headquarters in that far-off land, the story of a new-found mining district, where mountain peaks were ribbed with silver, and valleys teemed with virgin gold. Such were the stories that caused hundreds of men to seek their fortune in Sierra Mojada, and to return heaping curses, loud and deep, upon the vivid imaginations that had evolved the glittering fiction. Nevertheless, the rumors had some foundation of truth. The ribs of silver exist, if not the placers of gold; and a flourishing town, of some three thousand people, with two leading mining companies and several smaller ones, in operation, represents what was permanent in the excitement of 1879. Geographical Situation. The town of Sierra Mojada is situated in the State of Coahuila, Republic of Mexico, in latitude 27' 24' N., and longitude 26' 40' W. of Washington, 4' 36' W. of the City of Mexico, and 103' 43' TV. of Greenwich. It lies about 70 miles, in an air-line, N. E. of Escalon station, on the Mexican Central Railroad; but by the present wagon-road, which makes a long detour to turn the mountain range, the distance to the station is about 105 miles. The nearest towns are Huajuquilla, in the State of Chihuahua, about 125 miles due west, and Cuatro Cienegas, in the State of Coahuila, 112 miles to the eastward. Between these points and the town of Sierra Mojada, and to the north of this town, the country is an immense desert, entirely uncultivated, almost uninhabited, and very little known. This

Jan 1, 1887

Discussion of the paper of S. E. Bretherton, presented at the Butte meeting, August, 1913, and printed in Bulletin No. 80, August, 1913, pp. 1481 to 1487. S. E., BRETHERTON, San Francisco, Cal.:-Since preparing my paper, our chemist, F. L. Wilson, has been experimenting with Leadville, Colo., oxidized zinc ore and Leadville zinc sulphides containing lead, operating upon 40-1b. lots at a time. His results on Leadville sulphides are as follows: The raw ore contained a trace of gold, 5.04 oz. of silver, 19.1 per cent of zinc, and 7.24 per cent of lead. After roasting the ore contained a trace of gold, 5.72 oz. of silver, 0.75 per cent of copper, 21.7 per cent of zinc, and 8.29 per cent of lead. The loss in weight by leaching was 38.8 per cent. The extraction was 42.8 per cent of the copper, 80.6 per cent of the zinc, 7.1 per cent of the lead, 0.64 per cent of the silver, and no gold. The little .silver that is extracted would be thrown down with the copper when precipitating it from the zinc and both thrown hack into the residue to be smelted. There would be no trouble in smelting the residue with nearly all the sulphur eliminated and containing less than 7 per cent. of zinc. On zinc carbonates containing silicates the results are not satisfactory. H. O. HOFMAN, Boston, Mass. (communication to the Secretary*) :¬The paper by Mr. Bretherton upon the application of ammonia and carbonic acid to the recovery of zinc as oxide from roasted sulphide ore is of interest to me, as the first installation of the Schnabel process for the extraction of zinc from a mixture of zinc oxide, lead oxide (with some cupric oxide), and pellets of enriched lead, produced in steaming liquated zinc-silver-lead crust of the Parkes process, was made at Lautenthal, Harz mountains, where I was chemist. In that capacity I carried out numerous experiments on the Schnabel process, was active in the erecting of the plant, and later had charge of it. After the Lautenthal plant had been in operation for some time a similar one was built at Hoboken-les-Anvers, but both have been abandoned, as the wet process could not compete with the distillation of the liquated zinc-silver-lead crust, now used universally in the Parkes process.

Jan 11, 1913

By Henry E. Wood

In my opinion, the concentration of minerals by flotation is the most interesting problem in ore-dressing, and will command eventually far more consideration than it has at present. For many ores it furnishes a complete method of concentration absolutely independent of specific gravity, and thus simplifies the milling of many difficult combinations. Not having to recognize the influence of specific gravity, we are also able to dispense with some of the complications resulting from classifying-conditions. Where flotation cannot be used for a complete separation of the minerals from the gangue, it will be found, in nearly all cases, to save those portions which are generally lost by reason of their fine state of division. For this reason, it should be looked upon mainly as an aid to general concentration, although there are many ores so well adapted to flotation that more than 90 per cent. of the valuable metals can be recovered from them in one operation by this process. In presenting the results of my investigations in flotation, I have endeavored to theorize as little as possible. That side of the subject has been extensively discussed by others. My earliest work with flotation was done in 1895, when I used various oils, grease, soap, etc., with results that were remarkable. I did not realize then that with water alone equally good separations could be made. Up to 1906, my endeavors were confined to attempts to keep the concentrates on the tables well wetted and away from exposure to the air. In common with others, I observed that when there mas any obstruction in the wash-water on the table of sufficient size to divert the water to either side, the concentrates collected, and, on exposure to the air, would promptly float away. This convinced me that the sulphides were all good "swimmers," and that if,

Jan 1, 1913

By B. M. Larsen, T. E. Brower

In an earlier paper1 we discussed a simple, rapid method of taking samples of liquid steel and analyzing them for oxygen, which, though possibly not absolutely accurate (as is likewise true of all other methods), certainly yields results that are satisfactorily consistent. Accordingly, samples from hundreds of heats ill different shops were analyzed for oxygen, with results sufficient in number to be handled statistically and permit estimation of some general trends. Measurements were made in acid as well as in basic open hearths, throughout the refining period, to learn how stirring, blocking, adding ore or lime or sand, affects the oxygen content of the bath; we also followed the changes brought about by tapping, teeming, and deoxidizing. Some of these results, discussed in an earlier paper,2 bring out the dominant role of the carbon-oxygen reaction in regulating degree of oxidation both of metal and of slag, also the marked variability of concentration of dissolved oxygen [0] in excess of that which would be in equilibrium with carbon and with carbon monoxide at a partial pressure of one atmosphere. As a logical beginning on this complex problem, we take up in the present paper the variability of this excess oxygen, A[O], when other factors are as constant as they ever are in open-hearth operation; namely, toward the end of the refining period, when the bath may be regarded as in the comparatively steady state it approaches in absence of disturbing factors. This condition was chosen because by that time the significant reactions, except carbon oxidation, between slag and metal have come to substantial equilibrium; this facilitates interpretation of the complex situation and thus perinits more definite conclusions to be drawn. This excess concentration of oxygen, A[O], in the metal is needed, of course, to make the steelmaking process go at a reasonable rate; alternatively it may be regarded as a measure of the virtual pressure increment above one atmosphere, or of the degree of supersaturation, of carbon monoxide in the metal. According to our measurements, the excess concentration A[0] in liquid steel varies from about 0.009 to 0,035 per cent oxygen by weight. It is quite sensitive to change of conditions, being altered temporarily by operations such as stirring with green poles, additions of ore, lime, or sand; but as the disturbance works itself out, it resumes a level within the intermediate range characteristic of the steady state. The conditions most common in average furnace practice are covered by the following: i[O] Usual Per Cent Oxygen by Conditions Weight 1. Vigorous lime boil........... o.oog-0.01s 2. Steady state................ o.or;-0.025 3. Working of ore.............. o.023-0.035 Thus when the bath can be regarded as in a reasonably steady state—that is, when it is boiling normally, is at proper temperature with a well-shaped slag, and has been free from disturbing effects during the preceding half hour—A[0] returns from

Jan 1, 1948

By B. M. Larsen, T. E. Brower

In an earlier paper1 we discussed a simple, rapid method of taking samples of liquid steel and analyzing them for oxygen, which, though possibly not absolutely accurate (as is likewise true of all other methods), certainly yields results that are satisfactorily consistent. Accordingly, samples from hundreds of heats ill different shops were analyzed for oxygen, with results sufficient in number to be handled statistically and permit estimation of some general trends. Measurements were made in acid as well as in basic open hearths, throughout the refining period, to learn how stirring, blocking, adding ore or lime or sand, affects the oxygen content of the bath; we also followed the changes brought about by tapping, teeming, and deoxidizing. Some of these results, discussed in an earlier paper,2 bring out the dominant role of the carbon-oxygen reaction in regulating degree of oxidation both of metal and of slag, also the marked variability of concentration of dissolved oxygen [0] in excess of that which would be in equilibrium with carbon and with carbon monoxide at a partial pressure of one atmosphere. As a logical beginning on this complex problem, we take up in the present paper the variability of this excess oxygen, A[O], when other factors are as constant as they ever are in open-hearth operation; namely, toward the end of the refining period, when the bath may be regarded as in the comparatively steady state it approaches in absence of disturbing factors. This condition was chosen because by that time the significant reactions, except carbon oxidation, between slag and metal have come to substantial equilibrium; this facilitates interpretation of the complex situation and thus perinits more definite conclusions to be drawn. This excess concentration of oxygen, A[O], in the metal is needed, of course, to make the steelmaking process go at a reasonable rate; alternatively it may be regarded as a measure of the virtual pressure increment above one atmosphere, or of the degree of supersaturation, of carbon monoxide in the metal. According to our measurements, the excess concentration A[0] in liquid steel varies from about 0.009 to 0,035 per cent oxygen by weight. It is quite sensitive to change of conditions, being altered temporarily by operations such as stirring with green poles, additions of ore, lime, or sand; but as the disturbance works itself out, it resumes a level within the intermediate range characteristic of the steady state. The conditions most common in average furnace practice are covered by the following: i[O] Usual Per Cent Oxygen by Conditions Weight 1. Vigorous lime boil........... o.oog-0.01s 2. Steady state................ o.or;-0.025 3. Working of ore.............. o.023-0.035 Thus when the bath can be regarded as in a reasonably steady state—that is, when it is boiling normally, is at proper temperature with a well-shaped slag, and has been free from disturbing effects during the preceding half hour—A[0] returns from

Jan 1, 1948

By E. J. KENNEDY

THE 142D MEETING of the Institute is rapidly shaping up with splendid prospects of a strong technical program and the lighter side of this annual occasion amply provided for. The date is February 20 to 23. The technical sessions will be held in the Engineering Societies building; the smoker-dinner, the informal dance, and the annual reception and dinner, at the Commodore Hotel, Monday, Tuesday and Wednesday respectively. The news to date on the technical side is as follows: Mining Methods-Subsidence The Mining Methods Committee has prepared an interesting program which will be divided into two sessions to be held early in the week. At the first there will be papers on mining methods and development, including a description of the "Sinking and Equipment of No. 2 Shaft at Minas de Matahambre," by Dudley D. Homer and R. H. Cromwell. They describe in considerable detail the equipment used and the practice followed in sinking this important shaft, giving detailed costs and performance figures. Hoist¬ing ?arrangements and mining practice at the "Red Ore Mines of the Woodward Iron Co. at Bessemer, Ala.," are described by Tenny C. DeSollar, superintendent of mines, in a second paper. At this session of the Mining Methods Committee, H. M. Roche and R. E. Crockett, of the Committee on Eastern Magnetite Mining and Milling Methods, will present their paper, "Iron Ore Mining at the Scrub Oak Mine." This mine is in the highlands of New Jersey about 40 miles west of New York City. Prof. Robert K. Warner of Yale University will present a paper on "The Selection of a Mining System," which should have an interesting discussion. Pierre R. Hines, of Portland, Ore., will present, with stereopticon slides, his paper on "The Owyhee Tunnels, U. S. Reclamation Project, Owyhee, Oregon," describing one of the recent irrigation undertakings.

Jan 1, 1933