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By D. Coutsouradis, L. Habraken, P. Nicolaides

The TTT curves of 0.1 pct C, 13 pct Cr steels containing up to 12 pct Co have been determined in order to establish whether the effect of cobalt is similar to that observed m plain carbon steels. It is shown that cobalt increases the incubation time and decreases the transformation rate, though not in an uniform way. The bainitic transfornation is displaced to lower temperature and overlaps partially the martensitic zone. ThE effect of cobalt on the transformation of a plain carbon austenite has been studied by many investi-gators.'-3 It was shown that cobalt displaces the TTT curves to shorter times and diminishes the harden-ability. The interpretations given for this effect of cobalt are conflicting. According to E. Houdremont,4 cobalt increases the transformation rate of austenite because it increases the diffusion of carbon as shown in the experiments of E. Houdremont and H.Schrader,' R.Smoluchowski,5 and M. Blanter.6 On the other hand, M. Hawites and R. Mehl3 deny on the basis of their own experiments any effect of cobalt on the diffusion of carbon and they assume that an explanation should be found in an eventual effect of cobalt on the mechanism of nucleation and growth of pearlite. W. C. Hagel, G. M. Pound, and R. F. Mehl7 have shown by calorimetric measurements that cobalt increases the free energy of the austenite-pearlite transformation in an eutectoid steel and this result explains qualitatively the observed effect of cobalt on the rate of nucleation and growth of pearlite. The purpose of this research was to see by determination of TTT curves, if this same effect exists in 13 pct Cr steels. EXPERIMENTAL PROCEDURES The preparation of the alloys was carried out in an

Jan 1, 1960

By A. R. Powell

Four, general methods have been used in the study of the decomposition of coal. The first has been directed toward the processes of coal formation, the second has been by means of microscopic studies, the third from the data of destructive distillation, and the fourth has made use of various solvents. Applying these methods to the sulfur of coal, it has been found that the organic sulfur of plant and animal life enters into the formation of coal and remains in organic combination in the final product. The inorganic sulfur is almost entirely combined as iron pyrites and marcasite. The infiltration of hydrogen-sulfide waters is doubtless a large factor in these combinations. Sulfates are found in very small quantities except where free oxygen has entered the coal strata. The mechanical mixing of detritus with the early coal material is another source of sulfur. In this case the sulfur is distributed in microscopic particles throughout the mass. In destructive distillation, a part off the sulfur comes off as hydrogen sulfide and various thiophen compounds, but this furnishes little information as to the nature of the sulfur compounds in the coal itself. The use of solvents has given valuable data concerning the sulfur compounds in coal. Fremy1 and later E. Guignet2 noted the action of alkaline solutions on coal after treatment with nitric acid and Anderson and Roberts3 showed' the presence of large quantities of organic' sulfur in the extract so obtained. In a study of the phenol extract of coal, Parr and Hadley4 found organic sulfur in the soluble organic material. These investigations proved the presence of organic sulfur in coal in addition to the inorganic forms, such as iron pyrites and sulfates. T. M. Drown5

Jan 9, 1919

By G. S. Brooks

The tendency of the oxides of such metals as aluminum, zinc, chromium, and calcium to form compounds at high tempera tures with iron oxide is well established by past investigation. Data of this reaction, as developed in laboratory research, have been contributed by Burleigh, Hofman, and Wells, in America, and by many others abroad. A partial bibliography of the subject is appended. From these authorities we learn that the ferric oxide here has the function of an acid, giving in the case of ZnO a zinc ferrite, with a normal composition of ZnOFe2O3 This formation of zinc ferrite particularly affects the success of such processes as leaching or magnetic separation, and thus becomes practically important to the metallurgist. But the meager existing data do not entirely agree; and quantitative results from muffle-practice are conspicuously absent. Furthermore, it being of some general importance to the zinc smelter in both roasting and reduction, the following few notes of operations oil a commercial scale are contributed: I. Physical Properties of Zinc Ferrite. As formed for the most part synthetically by investigators, zinc ferrite exhibits characteristic physical properties, such as octahedral crystals, dark color, and a density over 5, together with a slight magnetic attractability. In examining with the microscope many products of mechanical muffle-roasting kilns, it is, however, impossible to find individual grains which can be identified as consisting entirely of zinc ferrite. The variety of colors, especially where each grain of blende was mechanically free from marcasite, rather conveys the impression of a partial ferritization of the grain. One side or end, for example, may often have the hard, dense surface and dark red to black color of the ferrite, while the balance shows the usual light yellowish brown of a normal iron-free blende.

Jan 1, 1914

By B. G. Ricketts, A. Kelly, P. A. Beck

The isothermal kinetics (at 200" to 400°C) of subgrain growth and of softening were studied in a 99.997 pct pure Al crystal rolled to 80 pct RA, under conditions where recrystallization did not take place. It was found that the kinetics of subgrain growth and of softening were similar, and that the correlation between subgrain growth and softening was in first approximation independent of the annealing temperature. It has been shown by Heidenreich' by means of electron transmission microscopy and by Hirsch and Kellar2 by means of an X-ray microbeam technique that the crystals of heavily cold-worked polycrystalline aluminum consist of subgrains of approximately 2µ diam, which are slightly disoriented with respect to each other. This substructure is found on cold working at room temperature, without annealing. A preliminary study has been previously published3 of the softening upon annealing at 350°C of a heavily cold-rolled aluminum single crystal. Softening and X-ray line sharpening for such a rolled aluminum crystal were later studied in more detail as a function of annealing time and temperature.4 Perryman5, 6 has studied the recovery of polycrystalline aluminum after cold rolling. By means of phase contrast microscopy he found that the subgrain size increases with the annealing temperature but does not alter very much with annealing time at a given temperature. In the present work further study was made of softening as a function of annealing time and temperature and subgrain sizes were determined by two different techniques in an attempt to find any correlation that may exist between softening and subgrain growth. Subgrain size measurements were made both by the X-ray microbeam technique and by transmission electron microscopy. EXPERIMENTAL PROCEDURE For the X-ray studies specimens were cut from

Jan 1, 1960

By J. M. Adams

It is my purpose to give some of the results obtained by an experience of nearly seven years in working ores by the method frequently called the Washoe Process, and in several mills of which I have had charge, but principally in the Owyhee Mill, at Silver City, Idaho, which had twenty 650-pound stamps, and sixteen pans. I shall discuss here merely the mechanical details for working ores generally, subdividing the subject as follows : 1. Preparation of the ore for the stamps; 2. The crushing in the battery; 3. The settling of sand or pulp in vats or tanks; 4. The treatment in the pans; 5. The results obtained in settlers, agitators, and concentrators; 6. The straining of quicksilver, cleaning of amalgam, and retorting; 7. The saving of slimes and their subsequent treatment; 8. The loss of quicksilver. For descriptions of the various kinds of orebreakers, stamps, tanks, pans, settlers, etc., I must refer to the various works on these subjects, prominent among which are the reports of the United States Commissioner of Mining Statistics,and the volume on "Mining Industry," the third volume of the United States Geological Survey on the Line of the Fortieth Parallel through the gold and silver bearing regions of the great West, undertaken under the able guidance of Clarence King, assisted by Mr. James D. Hague and others. In this discussion it will be assumed that the general arrangement of the quartz mill is understood; and the question will be treated how to secure, from such a mill, the greatest economy in working, combined with the largest results. This place seems fittest for a single preliminary suggestion—namely, that there should be double "floors" throughout the mill, so that nothing can sift through and be lost.

By John L. Schroder

INTRODUCTION-SYSTEM DESIGN The design of an underground mining operation requires the integration of transportation, ventilation, ground control, and mining methods to form a system which provides the highest possible degree of safety for mine personnel; the lowest cost per ton of product ; the most suitable quality of final product, considering its intended use; the maximum percent recovery of the reserve, consistent with cost and subsidence rights ; and the minimum disturbance to the environment. The selection of mining method is generally the controlling factor in overall mine design. Some important considerations in the choice of mining method are: 1) Depth of cover over the coal seam. 2) Strength and thickness of rock strata in the overburden. 3) Characteristics of the coal seam, including thickness, nature and location of impurities or irregularities, dip (or pitch), nature and direction of cleavage, hardness, and structural strength of the coal. 4) Nature and strength of the immediate roof (top) over the coal seam. 5) Nature and strength of the floor (bottom) under the coal seam. 6) Presence and amount of explosive gas (methane). 7) Quantity of water likely to be encountered in the mining operation. 8) Any previous or concurrent mining in seams above or below the coal seam to be worked. 9) Any restrictions on recovery required for subsidence control. Topographical and geological reports and maps of the area are usually available from state and federal geological surveys, and contain excellent general information to guide more detailed investigations. Exploratory drilling, and the plotting and analysis of the information thus obtained, are essential steps in any development program, and aid in the correlation and evaluation of information gained by other means. Other good sources of information are operating coal mines that may be in the same

Jan 1, 1981

By Frederic P. Dewey

It is common to blame irregular assay results upon volatilization and much has been written upon the subject, but there is no real evidence that, in a properly conducted assay, the loss of either gold or silver by volatilization is sufficient to affect appreciably the result, even when arsenic or antimony may be present. Bulk assays of flue dust from assay muffles have been published, but the data given are totally insufficient to even approximate the volatilization from a single assay; and such figures as we have indicate the volatilization to be extremely small. Diligent search in the literature and wide inquiry among assayers and instructors have failed to produce a single case where the litharge volatilized in making an assay has been collected and assayed for gold and silver. Having attempted to do this, with most indifferent success, I am not surprised that this has not been done. While various textbooks give volatilization as a cause of loss in cupella-tion, it may safely be said that in the rare cases where this volatilization is sufficient to affect appreciably the result it is due to excessive temperature. Percy' says "The loss of silver by volatilization during cupellation is very slight (unless the temperature has been much too high), and may be disregarded." This statement is repeated by the Beringers2 and Smith,3 who includes gold with silver. Mitchell4 says the litharge fume rarely contains over one ten-thousandth of silver. Campredon5 ays that at a proper temperature no silver is lost by volatilization. Primarily, excessive temperature may be due to too high general temperature in the muffle; but it may often be due to temperature localized within the bead by oxidation of the metals and this may be influenced by other causes than the general temperature. I have shown an ex-

Jan 1, 1921

By S. G. Dixit, A. K. Biswas

The flotation and adsorption behavior of ilmenite, monazite and zircon have been studied with sodium oleate as the collector and pH as the principal variable. The maxima in the flotation and adsorption properties of any of the above minerals fall within similar pH ranges. The bell shaped pH versus adsorption magnitude (r) curve is explained on the basis of collector concentration (Co and the concentration of hydroxyl ion (COH-) acting as the depressant. An equation of the type: 1 =KiCor~K2 Coh-/Coi-is proposed to account for the experimental data. The beach sand deposits along the sea coast in Southern India contain ilmenite, monazite, zircon, rutile and sillimanite as valuable minerals while quartz, garnet, shells and traces of hornblende form the gangue. A typical composition of the deposits is reported to be as follows:' Ilmenite 75%, Zircon 4-6%, Rutile 3-4%, Monazite 2 - 4%, Garnet 2 - 5% and the rest 8 -10%. Selective flotation of beach sand constituents has been reported by many workers.2-4 The fatty acid soaps have been invariably used as collectors. It is seen that all the valuable constituents of the beach sand are efficiently floated by soap collectors such as sodium oleate. In order to selectively float the beach sand constituents, it is necessary to use some depressants such as sodium silicate.3 The physicochemical parameters that govern the flotation of these minerals are yet to be studied in detail. In the present article, the findings on the parallel studies on the flotation and adsorption of the systems — ilmenite-sodium oleate, monazite-sodium oleate and zircon-sodium oleate — are being reported. In these correlative studies on adsorption and flotation of beach sand minerals, ilmenite (FeTiO3), monazite (Ce, Dy, Nd) PO4 and zircon (ZrSiO,) have been selected because they represent three important

Jan 1, 1970

By Charles Brush

THE general subject of accurate pyrometry, its great development in recent years, and the importance of its application in arts and manufactures is so ably treated in other papers that this paper will bee confined to a resume of some research work on certain temperature effects in carbon and other steels, some of which appear to, be new. The results of these researches are embodied in several papers presented to' various scientific societies during the last few years, most of them under the general title of Spontaneous Generation of Heat in Recently Hardened Steel.1 Several years ago, when studying the behavior, tinder certain conditions, of specimens of hardened tool steel, I observed that they all spontaneously generated a small quantity of heat, the rate of generation diminishing from day to day for several weeks before generation became imperceptible in the sensitive calorimeter used. In each case the steel had been hardened only a few days prior to its use. It seemed highly probable that the generation of heat was associated with some sort of "seasoning" or incipient annealing process, perhaps accompanied by slight changes of volume, and that it would be most rapid immediately after hardening. I subsequently investigated this curious phenomenon more fully. Twelve ½ in. round bars of tool steel, 5 in. long and with machined surfaces, were hardened by heating to high cherry red in a reducing atmosphere of a gas furnace and quenched in cold water. The bars then had a thin strongly adhering coating of black oxide. They were next stirred in a large quantity of water at room temperature, to acquire that temperature, wiped dry, and oiled with heavy, neutral mineral oil to prevent generation of heat by further surface oxidation, wiped free of excess of oil and placed in the copper cylinder of a heat-insulated box.

Jan 9, 1919

By K. Thirumalai

Although the term "spalling" has long been known, Norton l first referred to its usage for the fracture or disintegration of materials subjected to rapid temperature changes. Spalling of ceramic materials at high temperatures has received attention in the past.2-4 Removal of the char formed during ablation in reentry of space vehicles has been referred to as mechanical spalling.5 The first experiments to evaluate the process of rock fragmentation by thermal spalling were conducted by Stoces6 using a series of gasoline burners on the quartz veins of the Zinnwald deep mines in Germany. After the development of rocket-jet burners, the principles of thermal spalling combined with high fluid momentum found wide practical application in rocks. The well-known jet piercing process for drilling blastholes in taconite and for jet channeling in the quarrying of granite are among the more notable of these application.7 For the purposes of this study, thermal spalling or spallation of rocks is defined as progressive failure caused by thermal stresses induced by a sudden application of heat from a high temperature heat source. Gray observes that the size of the spall is dependent on the pattern of induced thermal stresses before failure. The spallability or the relative susceptibility of rocks to failure by thermal spalling is a complex but potentially useful parameter for qualitative comparisons. Fundamental differences exist in the degree of spallability among different types of rocks. Accurate prediction of spallability of any particular rock has so far not been possible. Measurement of the state of stress and temperature in the rock during the rapid thermal spalling process poses difficult problems that must be solved. Identifying the parameters that influence the thermal spalling proc-

Jan 1, 1970

By Carl Davis

A description is given of grinding practice on the Rand and of experiments made to improve that practice. The paper includes a description of the experimental plants and methods and the results obtained. THE first tube-mill on the Rand was put into operation in May, 1904, at the Glen Deep Mine. From that time onwards, tube-mills were added to various plants, although little was known regarding the capacity of a given tube-mill when working on banket ore. Within a few years, however, the so-called standard size (length of shell 22 ft. 0 in. diameter 5 ft. 6 in.) was generally used until the last year or two. Practically the only exceptions were about 30 tube-mills having a length of 16 ft. and a diameter of 6 ft., and a few open-end mills of the roller-supported type. Most of the information obtained during the last 15 years has been obtained with mills of the standard dimensions. The adoption of the tube-mill as an accessory to the stamp mill was rapid; and where 3 tube-mills were working on the Rand at the end of 1904, 244 were in use seven years later.1 By 1910, good practice provided 1 tube-mill for 20 stamps of 2000-lb. falling weight. The horsepower of the motors driving the tube-mills had increased from. 80 to 100 and then to 125 at this date. Broadly speaking, current practice at that date aimed at a final product of which 60 per cent. was suitable for sand treatment and 40 per cent. for slime. The sand grading was +60 mesh, 6 per cent.; +90 mesh, 25 per cent.; -90 mesh, 69 per cent.; and the slime grading -200 mesh, 2 per cent.; -200 mesh, 98 per cent.

Jan 12, 1924

By H. O. Hofman

The sudden decease, April 1, 1910, in Chicago, of Dr. Franklin R. Carpenter was a shock to his many friends. He died in his sixty-second year, of heart paralysis. To most fellow-members of the Institute who have followed the progress of the last twenty-five years in the mining and treatment of non-ferrous ores, the work of Dr. Carpenter in that line is familiar; but very few, even of those who knew hinl well in the later years, are acquainted with his earlier struggles to satisfy an inborn hunger for knowledge. The story of his life resembles that of the pioneer who opens up new country; overcoming hardships with indomitable courage, meeting doubts and difficulties with an alert and open mind, and exercising in the face of reverses an unconquerable perseverance. It seems appropriate to place on record in the Transactions a brief outline of the life and work of this eminent engineer. During the past 15 years of his life Dr. Carpenter was much interested in genealogy. In the pursuit of this study as an avocation, he traced his own ancestry to the time when ((Hugh," called "le Charpentier" on account of the dexterity with which he had swung his battle-axe as a crusader, settled in Sussex on lands received from William the Conqueror. The Carpenters came to this country with William Penn. A prominent member of the family was Joshua Carpenter, the founder of Christ Church, Philadelphia. Dr. Carpenter's branch of the family moved from Pennsylvania into that part of Virginia which is now West Virginia, where his grandfather settled in Harrison county, while the grand-uncle went further west, and built the first iron-furnace at Hanging Rock, Lawrence county, Ohio. In fact, since early times, the Carpenters appear to have been iron-masters. Franklin R. Carpenter mas born, Nov. 5, 1848, in Parkers-

Jan 1, 1911

By George J. Young

The recurrence of mine-fires in Nevada during the past decade is not only a matter of interest, but also one of considerable concern to engineers and mine-managers. The more important fires may be enumerated as follows: Forman Shaft fire, Gold Hill, April 21, 1903; shaft-house, machinery, and shaft destroyed; loss estimated at $50,000; cause unknown. Union Shaft fire, Virginia City, July 14, 1904; shaft-house, machinery,and shaft in part destroyed; loss estimated at $100,-000; cause of fire stated as the careless throwing of a match in the rope-house. Sutro Tunnel fire, Virginia City, Jan. 27, 1909; 700 ft. of tunnel-timbering destroyed, and direct damage of $10,000; cause " probably electric wires." Belcher Shaft fire, Gold Hill, Aug. 9, 1910; shaft-house destroyed, machinery ruined, and upper part of shaft damaged; damage, $25,000; no cause given. Belmont Mine fire, Tonopah, Feb. 23, 1911; fire started ill winze; 17 men killed. Giroux Mine fire, Kimberly, Aug. 23, 1911; fire originated in shaft-station from unknown cause; 7 men killed, and $34,-521 damage caused. (Note 1.—On June 11, 1912, some time after the present paper was written, a fire broke out in the pump-room on the 2475 station of the Ward shaft, Virginia City. This fire was caused by the short-circuiting and exploding of the starting-switch on No. 5 pump. The oil in the switch was scattered about and set fire to the timbers and lagging of the pump-room. The pump-man in charge notified the surface, and the electric current was shut off. A hose was then turned on the fire, but the dense smoke drove the attendant out. Inspection by the electrician and the shaft-foreman, equipped with oxygen-

Jan 1, 1913

By José Geraldo Vieira

Companhia Vale do Rio Doce (CVRD), founded in 1942, is located near the town of Itabira, Brazil. Its iron ore deposits include over 500 million metric tons (mt) of high-grade hematite and about 2 billion mt of itabirite (banded rock formed by thin alternate layers of hematite and silica). These deposits are part of the Iron Ore Quadrangle, of which the overall reserves have been estimated at more than 30 billion mt. The magnitude of the project meant difficult early years for the company, including large investments, extensive railroad rehabilitation, and construction of ore port and ore handling facilities. Companhia Vale do Rio Doce was organized as a stock company, and 91% of its shares are presently owned by the Brazilian government. Financing has been accomplished in part through loans from international monetary agencies foreign banks, and foreign industry, as well as Brazilian banks. The company markets mainly abroad. In 1967, it exported 10.6 long tons (It) of ore, principally to West Germany, Japan, Netherlands, Italy, France, United Kingdom, and the United States. The Rio Doce geographic region where CVRD operates is strategically located among the large population centers of Rio de Janeiro, Belo Horizonte, Salvador, and Vitoria (Fig. 1). It covers an area of approximately 81,000 sq km in the states of Minas Gerais and Espirito Santo, and its population in 1968 was about 3.5 million. This region presents excellent prospects for development, with factors favorable for forestry, agriculture, grazing, and exploration for minerals other than iron ore, Electric power (hydroelectric plants) is available, as well as two main systems of transportation: the Rio-Bahia highway and the Vitoria-Minas Railroad. Pioneer activities at Itabira started about 1720 as small gold mining centers. The town is about 80 km northwest of Belo Horizonte and

Jan 1, 1969

By Mark J. Klein

The precipitation of nitrogen in quenched and aged CY-35 at. pct Re was followed by internal-friction and electrical-resistivity measurements. It is shown that the precipitation kinetics of nitrogen from solution are many orders of magnitude lower in this alloy than in chromium. The reluctance of nitrogen to precipitate from sol~ction can be attributed to the composilional r-eadjustnzents required in the z.icinity of a chromium nitrade particle for gowth to occur. AS part of an investigation of the mechanism by which rhenium increases the low-temperature ductility of chromium and other Group VI-A metals, it was of interest to compare the concentration of interstitial elements retained in solution in chromium with that of a ductile Cr-Re alloy. The presence of certain interstitial elements in chromium has been shown to decrease its ductility1-5 and, of these interstitials, nitrogen is believed to have the most detrimental effect on mechanical properties. Thus, a comparison of the disposition of nitrogen in chromium with that in a ductile Cr-Re alloy might provide information about the mechanism whereby rhenium enhances the ductility of chromium. In previous internal-friction studies it was shown that the equilibrium solubilities of nitrogen in chromium and Cr-35 at. pct Re did not differ greatly.= However, results indicated that the actual concentration of nitrogen retained in solution at ambient temperatures is likely to be considerably greater in the alloy than in chromium because the precipitation kinetics of nitrogen are greatly retarded by the addition of rhenium. The objective of this investigation was to study the kinetics of nitrogen precipitation in Cr-35 at. pct Re in greater detail and to obtain information concerning the mechanism of nitrogen precipitation in this alloy. The properties studied were internal friction and

Jan 1, 1967

By Brigitta Hassler

INTRODUCTION In the early 1960's research was begun in Sweden to improve the agglomeration of our domestic iron ore concentrates (5). Different agglomeration methods that were used in the building material industry were studied under the economic support from the Swedish Technical Council, the Swedish Board of Technical Development and by the Swedish industry. The research work was performed at the Division of Mineral Processing at the Royal Institute of Technology in Stockholm. All known agglomeration methods were reviewed and the methods were developed to produce superior quality agglomerates (6). The term cold bonding (in contrast to sintering) was introduced to describe the induration operation in these processes and this has been accepted internationally. Even though we used it mostly for steam autoclaving methods, it has come to describe a class of processes that use binding methods by pore filling. Schumacher in Germany discovered around 1907 that a strong material can be produced by mixing slaked lime with fine ground quartz and subjecting to a steam atmosphere under pressure at about 185ºC. This started development of lime-sandstone building materials and later on, in Sweden, the light-weight concrete. Schumacher also used the same reaction for briquetting iron ore concentrates by adding silica and lime, and autoclaving. The product seems to have been accepted for blast furnace burden and the process was used on an industrial scale until the 1920's. The sintering method has a small melting phase as diffusion medium and in the steam-autoclaving method a small quantity of water condensate at about 200°C serves the same purpose. Thus the induration process by the hydrothermal hardening methods is similar to that of sintering or heat treatment.

Jan 1, 1977

By J. M. Adams

IT is my purpose to give some of the results obtained by an experience of nearly seven years in working ores by the method frequently called the Washoe Process, and in several mills of which I have had charge, but principally in the Owyhee Mill, at Silver City, Idaho, which had twenty '650-pound stamps, and sixteen pans. I shall discuss here merely the mechanical details for working ores generally, subdividing the subject as follows: 1. Preparation of the ore for the stamps; 2. The crushing in the battery; 3. The settling of sand or pulp in vats or tanks; 4. The treatment in the pans; 5. The results obtained in settlers, agitators, and concentrators ; 6. The straining of quicksilver, cleaning of amalgam, and retorting; 7. The saving of slimes and their subsequent treatment; 8. The loss of quicksilver. For descriptions of the various kinds of orebreakers, stamps, tanks, pans, settlers, etc., I must refer to the various works on these subjects, prominent among which are the reports of the United States Commissioner of Mining Statistics, and the volume on "Mining Industry," the third volume of the United States Geological Survey on the Line of the Fortieth Parallel through the gold and silver bearing regions of the great West, undertaken under the able guidance of Clarence King, assisted by Mr. James D. Hague and others. In this discussion it will be assumed that the general arrangement of the quartz mill is understood; and the question will be treated how to secure, from such a mill, the greatest economy in working, combined with the largest results. This place seems fittest for a single preliminary suggestion-namely, that there should be double "floors" throughout the mill, so that nothing can sift through and be lost.

Jan 1, 1874

By Gherman Pavlovich Nikonov

Results of preliminary research on the use of small diameter water jets at high pressure for cutting rocks has demonstrated the possibility of effective cutting of anthracite. Detailed research has, therefore, been conducted at the Skotchinsky Institute of Mining to study the dynamics and structure of the small water jets and the mechanism by which they cut coal. One of the objects of this research was to obtain data for the design of a machine for cutting rock, based on the same principles as that for cutting coal. The productivity of water jet mining machines depends on the hydro- dynamic parameters of the jet. Therefore, the research on small diameter water jets was directed, initially to a study of the nature of the variation of these parameters, and to obtain a profile of dynamic pressure distribution over the section of the jet. As has been confirmed previously, the required jet pressure (to cut coal) lies in the range of 100 to 500 atmospheres. These pressures were utilized for the research. The diameter of the nozzle was changed as ~follows; 0.97; 1.24; 1.5; 2.17; 2.87; and 3.57 mm. Graphs showing dynamic pressures for each nozzle diameter and varied axial dynamic pressure were obtained over distances ranging from 2 to 70 cm from the nozzle. One of the most important hydrodynamic parameters of a jet, closely related to the dynamics of jet disturbance in air, is the magnitude of the axial dynhmic pressure. A study of the variation in this pressure with increasing distance from the nozzle led to the separation of the jet into three specific parts, which differ from each other not only in the nature of the change in dynamic pressure, but also in structural properties.

Jan 1, 1971

By B. T. Brady, Wilson Blake

One of the more widespread experimental procedures currently used in experimental rock and soil mechanics work involves the use of a short circular cylinder loaded axially between nonrigid end plates1-5 (Fig. 1a and b). It is widely recognized 6 that a number of undesirable features are connected with this test procedure ; the most noteworthy of these is the development of a nonuniform stress distribution throughout the specimen resulting from an elastic mismatch between the specimen and the end plates. In general, the end plates and specimen possess different elastic properties. As a result of this elastic mismatch, the uniform distribution of stress and strain applied to the end plates is altered at the interface, the degree of which is dependent not only on the magnitude of the elastic mismatch but also on whether there is any relative movement between the specimen and the end plate. A convenient measure of the elastic mismatch is the ratio (vp/Ep) / (v8/E3), where v and E are Poisson's ratio and Young's modulus and the subscripts s and p refer to the specimen and end plate, respectively. For most tests that use steel end plates, (v8/E8) is greater than (vp/Ep) ; i.e., the specimen tends to expand or contract laterally more than the end plates. Because of the frictional restraint offered by the end plates, shearing stresses are developed at the interface that, for compression testing, act inward producing a "clamping" effect (Fig. lc). The effect of this "clamping" is to produce a state of triaxial stress throughout the specimen. Fig. Id illustrates the coordinate system and stress nomenclature used. In a homogeneous, elastic two-dimensional plate loaded uniaxially at the edge, a uniform stress distribution is obtained at a distance from the

Jan 1, 1972

CONTENTS PAGE GEISMER, H. S.-Coal Washing Practice in Alabama. Discussed by William Kelly, H. S. Geismer, H. D. Pallister, L. E. Bryant, Milton H. Fies, Elmer F. Harris, James A. Barr, George G. Crawford, E. C. Wright, George S. Rice, R. V. Norris 1 MILLER, F. W.-Byproduct Coking in Alabama. Discussed by Theodore Swann 4 FIES, MILTON H.-Alabama Coal Mining Practice. Discussed by Milton 11. Fies, R. V. Norris, R. D. Hall, L. E. Bryant, George S. Rice, H. S. Geismer 5 MUSSEY, H. E.-Blast-furnace Practice in Alabama. Discussed by C. A. Meissner, Franklin H. Crockard, H. E. Mussey, W. H. Oldham 14 Coal Washing Practice in Alabama Discussion of paper of H. S. GEISMER, presented at the Birmingham Meeting, October 1924, and issued, as Paper No. 1363-C, with MINING AND METALLURGY, September, 1924. WILLIAM KELLY, Iron Mountain, Mich.-Is the dry-cleaning method used? H. S. GEISMER.-Neither the dry-cleaning process nor the Chance sand-liquid method has been tested in Alabama; but all other methods used for cleaning bituminous coal have been largely brought to perfection in this state. H. D. PALLISTER, Tuscaloosa, Ala.-Have you the results from the recent work on the tables with reference to fine coal? H. S. GEISMER.-None of the iron-producing companies has adopted the tables, though three commercial operators have installed tables within the last six months. I tried to learn the results, but they were not willing to release the data just now. At the mines producing domestic coal, fines present a difficult problem; until within the past six months all the fine coal was wasted. The operators are trying to recover some of it on the table. L. E. BRYANT, Rockwood, Tenn.-Is there any connection between the sulfur content of the sludge and the effect of the sludge on vegetation?

Jan 7, 1925