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By R. H. Marshall, J. Welchner, E. S. Rowland

THIS paper presents results on an exten¬sion into the realm of high-carbon steels of some work recently published' on the effects -of time at temperature, quenching temperature and prior structure on the hardenability of one 0.20 and four 0.40 per cent carbon alloy steels. It was shown at that time that unless the conditions of time, temperature and prior structure are substantially the same in performing the hardenability test as in conducting harden¬ing of parts in production, the correlation of hardenability information with the [ ] hardness and properties of production parts is often not of satisfactory accuracy. The general effects of these variables on the austenitic grain size, distribution of excess carbides and critical cooling rate have been known for many years and one or more have been investigated by Shepherd ,2 3 Davenport and Bain,4 Digges,5,6 Digges and Jordan,7 Post and associates' and Roberts and Mehl,9 to mention only a few. There has been no systematic investigation, however,' into the quantitative variations produced on the hardenability of commercial high¬carbon steels by changes in these factors of time, temperature and prior structure. PROCEDURE A plain carbon hypereutectoid steel, S.A.E. 52100 and Graph-Mo, a molyb¬denum-bearing high-carbon steel contain¬ing some graphite, were chosen for this investigation. The chemical analyses of these electric-furnace steels are given in Table I. [ ] The procedure used was exactly that reported previously,' hence the details will not be repeated here. Normalized (1650°F.) and spheroidized prior structures were utilized on all steels with hot-rolled and quenched (1600°F. oil) prior conditions added for the plain carbon steel. The end-quench test developed by Jominy10 was selected for use in this investigation and, with the noted exceptions, the American Society for Testing Materials standard. procedure was followed. The effect of time at temperature was examined at intervals of 0, 10 and 40 min. and 4 hr., and a few i6-hr. tests were run. Salt-bath heating of the specimens was employed to control and minimize the

Jan 1, 1944

THIS paper presents briefly some of the principal results of 3 ½ months field work during the summer of 1938 in the Chichagof mining district, southeastern Alaska. The report is preliminary and presumably will be followed later by a more complete report to be published by the Geological Survey. The paper is concerned principally with the structural geology of a block of steeply dipping graywacke as revealed underground in the Hirst Chichagof and the Chichagoff mines, the two principal mines of the district. The two mines have produced about $16,000,000 worth of gold and silver. The attitude of the graywacke, which is locally cut by dikes and sills of aplite, is remarkably uniform and trends about N. 62º W. The average dip is about 67º SW. The graywacke is cut by large faults, the best known of which are the Hirst and the Chichagof, whose average trends are about N. 30ºW. and average dips about 75º SW. The faults at some places split into the bedding of the graywacke and at others are deflected from their normal trends for considerable distances along the bedding. The relative movements along the faults was northwest and up at about 30º for the south- west or hanging-wall sides. The ore bodies are elongate quartz lenses in the faults. Most of the quartz is mineralized but locally large quartz masses are too low grade to be mined. The emplacement of the ore bodies appears to have been structurally controlled in large part by the intersections of the faults with the bedding surfaces. Places where the faults split or are deflected appear to have been particularly favorable places for ore deposition. There has been some post-quartz movements along the faults but it is thought that such movements have not been extensive enough to greatly modify the original positions and shapes of the ore bodies.

Jan 1, 1939

By C. A. Rowland, R. C. Nealey

Until recently there were very few dry grinding rod mills used. The early installations performed as anticipated. In the last seven years a number of dry grinding rod mills have been made, most of which have been used for grinding iron ore. The recent installations have not operated as anticipated in accordance with practices learned from wet rod milling. The paper does not establish any definite rules for the application of dry grinding rod mills but does attempt to establish some guidelines that can be followed. The paper reviews a number of flowsheets describing the problems encountered and some of the solutions found. Completely dried compared to partially dried feed is reviewed. Problems encountered in scaling up from pilot plant to production-size mills are described. Rod sizing, effect of rod length, rod bending, rod breakage, and rod tangling are discussed. While wet grinding rod mills have been used for 50 years to grind ores and make specifications sands, dry grinding rod mills have only recently come into significant use in the mineral industries. Among the materials now being processed in dry grinding rod mills are (1) lead sinter, lead slag, and limestone; (2) iron ore; (3) silica; (4) cement clinker; and (5) coke. Because the application of wet grinding rod mills was well understood at the time that dry grinding rod mills were introduced, the criteria and guidelines for selecting the former were carried over to the selection of the latter - in some cases with the anticipated results, but in many cases not. It is the purpose of this paper to describe, through a series of flowsheets, some of the recent problems encountered with dry grinding rod mills, to point out the solutions to these problems, and to set forth some guidelines for the selection and application of these mills. When dry grinding rod mills came into use, the following facts about their wet grinding counterparts were already well established: (1) The performance of large-sized mills can be accurately predicted from the performance of rod mills 5 or 6 ft in diameter. Wet grinding mills as large as 14 ft in diameter (inside shell) by 20 ft long with rods 19.5 ft long can operate satisfactorily.

Jan 1, 1970

By Arthur E. Hall

Tax operation of "softening" in lead refining is designed, as the word implies, to separate from the bulk of the lead the elements that tend to make lead hard. These elements, which invariably are present in argentiferous lead, interfere with the desilverization, and must be almost entirely absent in refined desilverized lead. They are mainly copper, antimony, arsenic and tin. The properties utilized in accomplishing this separation are the low solubility of copper or copper sulphide in lead at its freezing-point temperature, and the greater and selective affinity for oxygen of the other elements at temperatures of the order of 700° to 900' C., or, in the prcsence of sufficient, alkali, at a temperature of about 500' C. The major problems of softening lead bullion lie in the necessary subsequent treatment of the by-products of the primary operation, which contain, either chemically or mechanically, lead or reagents that must be isolated for market or re-use. Therefore an important objective of the primary operation must be the highest practicable concentration of these elements in the by-products. Within the past three decades, during which the writer has been engaged in lead refining, the technique of softening lead bullion has had as many variations as there were lead refineries. This was the result of the variation in composition and character of lead bullion recived. The writer has received for refining shipments of lead bullion varying as widely as indicated by the following table: Sb, Per CEnt As. Per Cent Sn, Per Cent Cu. Per Cent Ag. Oz. per Ton 1.00 0.05 nil 0.05 70 0.50 2.50 2.00 0.50 200 3.50 0.50 nil 0.30 350 At times these have been received uniformly and at other times irregularly with a variation from week to week as wide as those shown. Under such conditions, establishment of a universal softening technique presented many problems. Such variations existed because refinery tolls too often were based on a ton of bullion, whatever its composition, and

Jan 1, 1937

By W. W. Gerberich, P. L. Hemmings, V. F. Zackay

ThE strain-induced martensitic transformation may be used to attain desirable combinations of strength, ductility, and fracture toughness. One of the parameters is the relative stability of the austenite. For example, it has been shown by Zackay et al.1 that the volume percent of strain-induced martensite is related to the combination of strength and elongation obtained. It has also been shown that the degree of transformation is an important factor in the crack propagation resistance of metastable austenitic steels.2 Considering both tensile and crack-propagation tests, it was of interest to see if there was any functional relationship between the amount of strain and the volume of strain-induced martensite. Previously,9 it had been shown that at room temperature, there was a relationship between uniaxial tensile strain and the volume percent of resulting martensite given by The data were obtained by plastically elongating tensile samples to a certain strain and then measuring the field strength to determine the strain-induced ferromagnetic volume. This was accomplished for two conditions having yield strengths of 229 and 233 ksi. The nominal composition of this material was 9Cr-8 Ni-3 Mo-2 Mn-2 Si-0.25 C-0.09 N. In evaluation of the strain-induced martensite at a crack tip: the question arose as to whether Eq. [1] would also be valid under triaxial stress conditions. Tests were conducted on 1/2-in. thick plate material having a composition of 9 Cr-8 Ni-4 Mo-2 Mn-2 Si-0.27 C. It was found that sectioning, polishing, and etching of fractured specimens could reveal the strain-induced martensite occurring at a crack tip. Care had to be taken to minimize the final polishing steps so as to avoid a smeared layer of strain-induced martensite. The method for taking metallo-graphic samples from fractured crack-line loaded type samples is shown in Fig. 1. Observations of the strain-induced martensite occurring at room tem-

Jan 1, 1970

By C. Y. Wang

China now leads the world in antimony production, having contributed during recent years something over 60 per cent. of the world's production. The history of the antimony industry of China dates back to 1897 when the Tai Shing Co. was formed, under contract with the Hunan Bureau of Mines, for the smelting of the ore to crude; and in 1908 the Wah Chang Mining & Smelting Co. was formed for the smelting and refining of the ore and crude to regulus. The writer was then asked to take charge of the erection and control of this first plant for regulus production in China and has, since then, been more or less connected with the antimony industry in this country. This paper contains the results of many years' experience in connection with the Wah Chang Mining & Smelting Co., Changsha; the Pao Tai Mining & Smelting Co., Wuchow; the Loong Kee Smelting Works and the To-Cheng Smelting Works, Hankow; as well as information gathered from various other small smelters, scattered in different parts of the Provinces of Hunan, Hupeh, Kwangsi, and Kwangtung. An idea of the growing importance of regulus production in this country can be gleaned from the fact that, within a period of about 8 years, the export of regulus from Hunan alone jumped from 3 tons in 1908 to about 6000 tons in 1915; that a production of about 23,000 tons of regulus per year could easily be effected from all the smelters, as tabulated below, most of which were erected a year or two ago under the stimulus of the war booms, if the price at Hankow were to stay somewhere about $900 (Mexican) per ton, half of what it was at its height, thus enabling the utilization of ores from the hinterlands of the provinces; and even under the present ruling of prices and the closing of the less favored smelters, the production of regulus should not be less than 12,000 tons per year.

Jan 1, 1919

By Harold A. Linke

The following article presents notes and data compiled and computed by the writer for use in the determination of: size and slope of mill launders, details of junction boxes and downspouts, and distribution of pulp. It also includes pulp formulas, volume of discharge through bushings, paths of discharging streams, banking of turns and curves. In the design of a concentrating mill, the draftsman usually considers launders to the extent of providing ample "head" for transmission of pulp from one department of the mill to another. The superintendent of construction aims to build his launders wide and deep, and on a slope steep enough to ensure positive flow. So launders are laid generally on too steep a slope, with the result that the repair gang works to maintain launder bottoms and sides against the erosive action of the conveyed pulp. To this end many kinds of liners have been devised: concrete, mastic, white iron, glass, rubber. True, the reduction of slope to the point where a pulp will flow with minimum wear, will minimize labor and expense; but when the desired slope is not predetermined, the millman hesitates to readjust his launder slopes by cut-and-try methods. To the end that the desired size and slope may be found readily, the writer has: (1) conducted experiments with pulps of different specific gravity, screen analysis and dilution; (2) gathered a few graphic data from standard reference works (such as Peele's Mining Engineer's Handbook and Taggart's Handbook of Ore Dressing); (3) computed several tables; and compiled results that have proved dependable for Utah Copper ore. It is quite possible that the following tables and graphs may not be applicable to all ores, but it is hoped that they may prove helpful, even in slight degree, in alleviating a portion of the trouble and migraine of some other millman. Launder Slopes The main object in the study of launder slopes is to provide grade steep enough to prevent "sanding" by a safe margin, and to avoid

Jan 1, 1943

By Harold A. Linke

The following article presents notes and data compiled and computed by the writer for use in the determination of: size and slope of mill launders, details of junction boxes and downspouts, and distribution of pulp. It also includes pulp formulas, volume of discharge through bushings, paths of discharging streams, banking of turns and curves. In the design of a concentrating mill, the draftsman usually considers launders to the extent of providing ample "head" for transmission of pulp from one department of the mill to another. The superintendent of construction aims to build his launders wide and deep, and on a slope steep enough to ensure positive flow. So launders are laid generally on too steep a slope, with the result that the repair gang works to maintain launder bottoms and sides against the erosive action of the conveyed pulp. To this end many kinds of liners have been devised: concrete, mastic, white iron, glass, rubber. True, the reduction of slope to the point where a pulp will flow with minimum wear, will minimize labor and expense; but when the desired slope is not predetermined, the millman hesitates to readjust his launder slopes by cut-and-try methods. To the end that the desired size and slope may be found readily, the writer has: (1) conducted experiments with pulps of different specific gravity, screen analysis and dilution; (2) gathered a few graphic data from standard reference works (such as Peele's Mining Engineer's Handbook and Taggart's Handbook of Ore Dressing); (3) computed several tables; and compiled results that have proved dependable for Utah Copper ore. It is quite possible that the following tables and graphs may not be applicable to all ores, but it is hoped that they may prove helpful, even in slight degree, in alleviating a portion of the trouble and migraine of some other millman. Launder Slopes The main object in the study of launder slopes is to provide grade steep enough to prevent "sanding" by a safe margin, and to avoid

Jan 1, 1943

By J. B. Newsom

In the Indiana limestone district, some 50 or 60 per cent of the merchantable stone in a quarry opening is waste, and only about 40 or 50 per cent of the stone from the opening is finally sold. So long as the present system of 'quarrying is used, the wastes measured and reported in this paper will continue. Comprehensive development of an entirely different method of quarrying, using wire saws for cutting, promises great improvement. Some of the savings to be expected are pointed out in the following pages. No attempt has been made to measure losses due to variations and natural flaws in the stone, since these vary greatly in different quarries, and accurate measurement would be difficult. The wastes that have been measured account for about 30 per cent of the total ledge, which leaves 20 or 30 per cent chargeable to unmeasured sources of loss. General Causes of Waste There are four general reasons for quarry waste: (1) the structure of the deposit, such as its shape, bedding planes, solution cavities and strain fractures; (2) efforts to quarry blocks which do not contain distinct color or textural variations; (3) the trade custom which permits purchasers to specify the size of the quarry blocks which they will buy, which is a matter of competition for business on the part of stone producers; (4) quarry methods, which cause the greatest amount of waste. Wide channeler cuts, hook holes, crooked splitting and uneven breaking on quarry floors are included in this category. Waste Due to Structure of Deposits The peculiarities of structure cannot be eliminated, but a chance for saving lies in quarrying to take advantage of them. The commercial deposits of Indiana limestone are lenticular masses from 20 to 70 ft. thick, and nearly horizontal. All of these deposits of good stone are in the Salem limestone, a bed in the sub-Carboniferous. The Salem is traversed by two systems of vertical fractures, a major system running from northeast to southwest and a minor system running from northwest to southeast. Where the stone is covered by an over-

Jan 1, 1932

By Carrol M. Beeson

Reasons are given for using a Boyle's-law porosimeter in conducting core analysis for either routine or research purposes. Among other things, it is pointed out that such a porosimeter permits the measurement of all basic properties on the same sample, thereby eliminating the sources of error inherent in the use of adjacent samples. References are made to investigations of gas adsorption on various porous materials, to show that the use of helium in Boyle's-law porosimeters reduces to negligible proportions the error due to the adsorption or desorption of the operating gas. Two Boyle's-law instruments are described. which permit accurate and rapid measurements of porosity. Schematic sketches and explanation:; are included, along with derivations of equations required in performing precise determinations. Summaries of data obtained during calibration are tabulated and analyses of the data are resented as indications of the precision and accuracy of each device. Comparisons are also shown for measurements made with each of the instruments on the same test pieces and cores. INTRODUCTION An accurate porosimeter, operating on the principle of Boyle's law. is of considerable value in the analysis of cores for either routine or research purposes. This is due primarily to the fact that the measurement of porosity with such an instrument leaves the sample free of contamination by any liquid. When used in conjunction with an extraction apparatus' for determining oil and water saturations, a Boyle's-law porosimeter permits the measurement of all basic properties on the same sample. This eliminates the sources of error inherent in the use of adjacent samples, or the necessity of determining porosity after all other properties have been obtained. Large errors may result from combining measurements made on adjacent samples in order to obtain a single property. This type of error is definitely involved when oil and water are measured with one sample, and the pore vo1ume is measured with an adjacent one. Furthermore, the source of error would be present to some extent, even if the analyst could choose the samples so they were truly adjacent from a geological standpoint. The use of adjacent samples in routine core analysis also necessarily decreases the probability of correlating core properties. For example, the chance of correlating the "irreducible" interstitial-water saturation with permeability, is bound to be greatly reduced by measuring these properties on "adjacent" samples. For research purposes, amplification is scarcely required concerning the greater flexibility of a method for measuring porosity which leaves the core free of contamination by any liquid. Even under those circumstances which require that the core be saturated with a liquid, a previous measurement of porosity with a gas is useful in determining the degree of saturation that has been attained in the process. Furthermore, for comparable accuracy, porosity usually may be determined more rapidly with a gas than with a liquid. This advantage of the Boyle's-law instrument is most outstanding when the determination time is compared with that required in obtaining porosity by evacuation of the core followed by saturation with a liquid of known density. Several porosimeters which operate on the principle of Boyle's law have been described2,3,4,5,6,7 in the literature. No comparison will be attempted between those instruments and the ones described herein. Before helium gas became readily available, Boyle's-law porosimeters were subject to an appreciable error due to the adsorption of the operating gas on the surface of the core solids. There is considerable direct and indirect evidence in the literature to support the contention that the adsorption of helium on porous solids is negligible at room temperature. In discussing the use of Boyle's-law porosimeters, Washburn and Bunting2 stated that "for most ceramic bodies dry air is a satisfactory gas, but hydrogen will be required in some instances. Helium could, of course, be employed for all types of porous materials at room temperatures or above." Howard and Hulett8 obtained evidence that the adsorption of helium was negligible at room temperatures, even on activated carbon ; for the density measured with this gas was unaffected by changes in pressure or by changes in temperature from 25 °C to 75 °C. For oil-well cores, Taliaferro, Johnson, and Dewees" obtained lower porosities with helium than with air, but apparently did not study helium adsorption. From the work of these investigators, it follows that the use of helium in Boyle's-law porosimeters reduces the error due to gas adsorption to negligible proportions. This makes it possible to construct instruments which permit the determination of porosity with (1) a high degree of accuracy, (2) with great rapidity, and (3) without contamination. THE KOBE POROSIMETER The fundamental design of the Kobe Porosimeter was developed by Kobe, Inc., which firm built about 12 of the instruments during 1936 and 1937. Since that time, seven or eight more have been constructed with their permission, making a total of about 20 that have been put into operation.

Jan 1, 1950

By Jay R. Burns

TWO magnesium sand-casting alloys are commonly favored in the United States. These are referred to as H and C alloys (Dow Chemical Co.) or 4Mz65 and AM260 alloys (American Magnesium Corporation). Both are of an aluminum-zinc-manganese type. H alloy contains 6 per cent aluminum and 3 per cent zinc and is characterized by relatively good toughness. C alloy contains 9 per cent aluminum and 2 per cent zinc and is employed where high yield strength and pressure tightness are required. Examination of magnesium castings poured in Europe and England,'J however, demonstrates that H and C alloys are replaced by .%8 and AZ~I, respectively. That is, A8 reprcsents a magnesiurn alloy having superior toughness while A291 is suitable for high yield strength and pressure-tight applications. The basic difference between the .Ameri-can and European alloys is that the foreign alloys employ a somewhat higher aluminum content and less zinc than is found in H and C alloys. The mechanical properties of the alloys, when divided into high and low-aluminum groups, are quite similar, as determined from separately cast foundry-control type test bars ,In this paper the decrease of mechanical properties caused by any given amount of microporosity is measured for H, C, A8, and AZ~I alloys. The relative susceptibility of each of the four alloys to microporosity is also determined. Typical mechanical properties and nominal chemical analyses are reported in Table I. The apparent similarities between the two alloys in each group have led to considerable discussion as to the relative merits of each of the compositions.2 Popular points for comparison between the alloys have been the relative susceptibility of each of the four alloys to microporosity6 and the effect of this microporosity on their mechanical properties. It is primarily intended, in this paper, to show the

Jan 1, 1946

By Jay R. Burns

TWO magnesium sand-casting alloys are commonly favored in the United States. These are referred to as H and C alloys (Dow Chemical Co.) or 4Mz65 and AM260 alloys (American Magnesium Corporation). Both are of an aluminum-zinc-manganese type. H alloy contains 6 per cent aluminum and 3 per cent zinc and is characterized by relatively good toughness. C alloy contains 9 per cent aluminum and 2 per cent zinc and is employed where high yield strength and pressure tightness are required. Examination of magnesium castings poured in Europe and England,'J however, demonstrates that H and C alloys are replaced by .%8 and AZ~I, respectively. That is, A8 reprcsents a magnesiurn alloy having superior toughness while A291 is suitable for high yield strength and pressure-tight applications. The basic difference between the .Ameri-can and European alloys is that the foreign alloys employ a somewhat higher aluminum content and less zinc than is found in H and C alloys. The mechanical properties of the alloys, when divided into high and low-aluminum groups, are quite similar, as determined from separately cast foundry-control type test bars ,In this paper the decrease of mechanical properties caused by any given amount of microporosity is measured for H, C, A8, and AZ~I alloys. The relative susceptibility of each of the four alloys to microporosity is also determined. Typical mechanical properties and nominal chemical analyses are reported in Table I. The apparent similarities between the two alloys in each group have led to considerable discussion as to the relative merits of each of the compositions.2 Popular points for comparison between the alloys have been the relative susceptibility of each of the four alloys to microporosity6 and the effect of this microporosity on their mechanical properties. It is primarily intended, in this paper, to show the

Jan 1, 1946

By A. Lee Barrett

The Maintenance Committee of the Coal Division of the American Institute of Mining and Metallurgical Engineers is presenting as a part of this report the second of a series of maintenance cost comparisons. The committee's purpose is to assemble maintenance costs on all equipment connected with mechanical operations at the face of coal mining and to arrange these costs by districts so that comparisons can be made between districts and within districts. The committee, this year, sent 35 questionnaires to representative coal companies who either reported last year or had advised specifically of the inability to report to last year's questionnaire primarily because of limited time. The response to the questionnaire this year as not as good as last year, only 20 of the 35 selected companies returning a completed questionnaire. This year's data have been compiled and combined with last year's data to present a comparison of the 1945 and 1946 costs of loading machines, shortwall cutting machines, universal cutting machines, service locomotives, shuttle cars, and mine cars. The same tabulation by districts is used as was used for 1945. As was indicated by last year's report there is considerable variation in the in cost of mining machinery in the various coal mining districts and due to this high variability it was not felt practical to attempt to arrive at weighted averages. Consequently, all average figures used in this report are straight averages. An analysis was made of companies reporting both this year and last year in an attempt to determine the trend in maintenance costs for different classes of equipment. Ten representative companies are used in this computation. Table I shows the average cost for 1945 and 1946. It is felt that the negative trend in the maintenance cost of universal cutting machines probably represents the effect of the purchase of a relatively large number of new machines in 1946 with little maintenance cost appearing during the first Year of operation. The grand total figure indicates an upward trend amounting to plus 18.7 pet. However, this figure is viewed with some suspicion because of the effect of the universal cutters decreasing maintenance cost and it is concluded that direct application of percentage increase should be made to types of equipment. In Table 2 covering maintenance costs of various types of mining equipment for 1945 and 1946 the results obtained in Table I indicating trends were applied to those

Jan 1, 1949

By E. R. Gilliand

KNOWLEDGE of a large number of the physical properties of the hydro-carbons is needed in the calculations and studies of the production engi-neer. Since experimental data on these properties of the individual hydrocarbons and their mixtures are available in only a relatively few cases, the use of generalized correlations has developed rapidly in the last decade. The generalized correlations of pressure, volume and tem-perature,1 enthalpy,2 and vapor-liquid equilibria,3 on the basis of reduced temperatures and pressures, are outstanding examples of this develop-ment. These correlations are of particular value to the production engineer interested in the flow of oil and gas, since they can be used to estimate the conditions under which segregation of phase occurs as well as the composition, density, and relative amounts of the phases. The technique of using the correlations for such estimations has been pub-lished by several authors¢ and will not be considered in this paper. A considerable number of data have been obtained to check the generalized pressure-volume-temperature correlations, and these data indicate that such relations hold for the hydrocarbons from methane to heptane. The accuracy is in general sufficient for most engineering pressure-volume-temperature calculations. However, the generalized correlations of enthalpy and vapor-liquid equilibria have in general been developed from the pressure-volume-temperature correlations by thermodynamic calculations and only a relatively few experimental data are available to check these calculated values. The calculations from pressure, volume and temperature are likely to lead to large errors in the calculated enthalpy and vapor-liquid equilibria. Thus, in the calculations of enthalpies, slopes of the pressure-volume-temperature data are employed, and determining these slopes can greatly amplify small errors in the original data. In the vapor-liquid equilibria calculations it is necessary to have the pressure-volume-temperature relations of the mixture, and the latter properties are much more questionable than those of pure components, particularly in the critical region. A considerable number of experimental data are

Jan 1, 1939

By David R. Mitchell, R. B. Hewes

MANY processes for cleaning coal that are in use depend primarily on physical properties of coal and refuse other than specific gravity and surface conditions relating to froth flotation. These properties are shape, coefficient of sliding friction, resilience, friability, magnetic susceptibility, and electrical conductivity. In many of these processes specific gravity does have some effect and many separators are designed to utilize more than one of the physical properties cited. Although the processes described herein do not have a widespread application, yet for specific coals and specific conditions, they are economically important. A problem confronting many coal-mining districts is the marketing of the slacks or screenings and dust passing the final sizing screens. Processes in commercial use installed primarily to increase the form value, and hence the market value, of these slacks and dusts include briquetting, packaging, and low-temperature carbonization. MECHANICAL PICKERS Machines utilizing shape, frictional resistance, and differences in resilience of coal and impurities are usually called mechanical pickers. They require a closely sized feed, therefore their use is confined to the pea, nut, and egg sizes. Various types of these devices are described by Berrisford, 1, 2 Taggart,3 and Peele.4 Shape In general, coal differs in shape from its accompanying dirt throughout the range of commercial sizes. Coal, breaking into roughly cubical particles, contains a greater number of axes that are approximately the same length than does the dirt. The latter, consisting of pieces of slate and shale and lenses of pyrite, is flatter in nature. Further, flat coal often has a dirty, slaty appearance, even though of high quality. Mechanical pickers known as flat pickers, or "flatters," are widely used in the Pennsylvania anthracite region to remove flat coal .from the final clean coal. This practice greatly improves the appearance of the final market product. Flat pickers for removing impurities or flat coal ("flats") are usually installed on shaker screens, shaking conveyors, and chutes. In Fig. 1 three

Jan 1, 1950

By R. Maddin, S. K. Tung

SUCCESS of the dislocation theory in formulating the transitional lattice theory proposed by Har-greaves and Hill in 1929' is well established for low angle grain boundaries. The theoretical work of Burgersa and Read and Shockley,3 together with the experimental observations of Aust and Chalmers4 and Parker and colleagues,6 leaves little doubt as to the structure of grain boundaries with differences of orientations up to between 15" and 20". Beyond these angles, the structure of the boundary is not so clear, and is still a matter for conjecture. There have been notable experiments devised from which the data could be used to calculate energetics for possible arrangements of atoms in forming a large angle boundary.6 Most of these experiments deal with diffusion through and along the grain boundary. The recent work of Rhines and Cochart7 and Rhines, Bond, and Kissel18 was concerned with the relative movement of grains in aluminum bicrystals under constant tensile loads with their boundaries aligned at 45 " to the tension axis. The gliding along the grain boundary was cyclic and began after an incubation period. The velocity of gliding increased with the sum of the angular difference, 8, between the operative slip direction in the conjugate crystals and the angular difference between the active slip planes as measured between their traces upon the grain boundary. The initial gliding rate varied with temperature, and the logarithm of the average gliding taken over a considerable period was a linear function of the reciprocal of the absolute temperature: the slope gave an activation energy of 11,000 ±1,000 cal per mole. Since the rate of grain boundary shear is sensitive to the misorientation of the grains themselves, as shown by several workers,7,8 it is suggested that further work of this type might be fruitful in adding information regarding the behavior of boundaries under stress. The techniques devised by Chalmers" added impetus to the facility for observing grain boundary behavior, in that they provided a simple means for producing bicrystals of predetermined orientation so that the angle of the boundary could be controlled,

Jan 1, 1958

By Albert H. Fay, William B. Plank

In practically all rock-excavation problem there is need for a careful study of the rock structure, its fault, cleavage or bedding planes, and even the texture of the rock itself. These studies should form the bases upon which an excavation method is selected and they should be carefully considered in predicting the amount and extent of the excavation. The need for such studies was forcibly illustrated in the problems involved in a cut made in 1929, along and underneath a 200-ft. high rock projection for a State highway near the City of Easton, Pennsylvania. The rock mass was badly faulted and also contained a number of cleavage planes at approximately right angles to the fault planes. Much of this structure was visible and could have been studied and analyzed before the work was begun. The State had rigid specifications as to finished grade and slope of cut, which apparently were made without reference to the geologic structure. The contractor complied with the specifications, under the close inspection of the State engineers. A tunnel blast was placed in the base of the cliff, with the result that 65 per cent more rock was broken than was intended by the specifications. About four years after the blast, the writers of this paper studied the circumstances surrounding the operation, to determine the cause of this excess excavation. Scope of Work The section of the roadway involved was about 200 ft. long and on a 6' curve. It was necessary to relocate points on the curve, from which all faults and cleavage planes were located and measured by the use of transit and clinometer. A plan (Fig. 1) showing the blasting tunnel, the roadway, and traces of the faults and cleavage planes on the level of the roadway, was prepared; also 13 cross-sections at varying intervals, showing the original face of the hill and the face after the blast. The original and final profiles of the rock face, taken from the plans of the State engineers, are shown in Figs. 2, 3 and 4.

Jan 1, 1937

By Ellen H. Richards

The water-supply of a country may be considered from three points of view: (1) its abundance and availability for agricultural purposes; (2) its chemical properties in their relation to manufacturing purposes; and (3) its quality and quantity as affecting domestic consumption. This paper concerns only those characteristics which may affect manufacturing and domestic uses. The so-called sanitary analyses deal not only with the common mineral elements found in water, but with organic matter and with those substances which, by their presence, indicate changes taking place through the agency of living organisms. Since these living organisms are frequently accompanied by others, capable, as are believe, of causing disease, the products of their action are looked upon with suspicion even when, as in the case of nitrates, that action may have taken place at a time long past. Therefore, upon the quality of the water-supply depends much of the history of a country, when rightly read, as well as much of its promise for the future. Thus, the hardness," or content of calcium and magnesium salts, gives a means of distinguishing at once between the waters traversing only igneous or other siliceous rocks and those coming from calcareous deposits. The presence of decomposing organic matter and intermediate products betrays a use of the water as the public carrier of refuse, which renders doubtful its fitness for domestic supply. In certain regions, one of the most valuable historical records is made by the relative amount of chlorine in the different waters. In the absence of rock-deposits carrying salt,, the chlorine present in rain and snow, and hence in mountainstreams and springs, appears to be derived from the air-borne, finely divided salt spray resulting from the beating of the ocean waves on the coast. If this be true, then the amount of chlorine found in a given water not contaminated with chlorides

Jan 1, 1902

By A. S. Nowick, A. E. Roswell

Anelastic measurements of atomic mobility in an Ag-Zn substitutional solid solution, make possible a study of the rate of decay of lattice defects frozen into the alloy by quenching. A WIDE variety of experimental evidence has accumulated recently in support of the belief that atomic mobility or diffusion in face-centered cubic lattices occurs principally through the movement of lattice defects, as contrasted to a mechanism by which two or more atoms directly exchange lattice positions. The most direct evidence, summarized in a recent review,' includes the Kirkendall-effect measurements and anelastic measurements on quenched alloys. Theoretical calculations' have focused attention on the lattice vacancy as the defect probably responsible for diffusion in the common metals. Later calculations3 have also shown the possible importance of combined pairs of vacancies in producing diffusion. The only defect that has been considered seriously, in addition to the vacancy and combination of vacancies, is the "interstitialcy" (an atom which has left its normal lattice position and entered an interstitial position) ; the calculated energy of formation of an interstitialcy in a close-packed lattice is too large to permit a reasonable probability for the occurrence of this defect In view of these calculations it may be tentatively concluded that the defects producing atomic movements are single or multiple vacancies. Anelastic measurements of atomic mobility in substitutional solid solutions provide a valuable method for the study of lattice defects. By means of this method it was first demonstrated' that defects may be frozen into a lattice by rapid quenching from high temperatures. (It was subsequently shown6 that resistivity measurements may also be capable of detecting the presence of frozen-in defects.) A summary of the principles involved in these anelastic measurements will now be presented. The anelastic method is based on a relaxation phenomenon in substitutional solid solutions, first discovered by Zenera in a brass and subseauentlv investigated extensively in a series of Ag-zn solid solutions.' This relaxation effect may be observed in the usual way either dynamically, as a peak in

Jan 1, 1954

By Robert W. Hunt

The American Institute of Mining and Metallurgical Engineers was the first American technical organization to consider steel-rail specifications and sections. If I am not mistaken, the first contribution on those subjects to the Proceedings of the Institute was presented by Prof. Thomas Egleston, in 1874, and was entitled "Investigations on Iron and Steel Rails made in Europe in the Year 1873.1" The next contribution was Dr. C. B. Dudley's report of his investigation for the Pennsylvania Railroad of the wear of steel rails in their tracks, in 1878, which contribution led to a very memorable discussion that extended through several meetings.2 In 1880, Mr. C. P. Sandberg3 presented an article on rail specifications and inspection and rail sections. This was followed, in 1881, by A. L. Holley,4 in his exhaustive report on the then used American rail sections. The next contribution, I believe, was made by myself5 at the Buffalo meeting, in 1888, on steel-rail specifications, which I followed,6 in 1889, by a paper on steel-rail sections. Since that time there have been numerous contributions to the Transactions of the Institute in relation to the manufacture of steel rails. The American Society of Civil Engineers officially took up the investigation of the relation of rail sections to the wear of car wheels in 1888. In the prosecution of this work, the Society appointed a special committee, whose labors extended through several years and resulted in an exhaustive report to the Society in 1893.7 Later, another committee was appointed to consider specifications for the manufacture of steel rails; the labors of this committee extended over a period of several years, a final reporta being made in 1910. It was my fortune to be the secretary of both of those committees. The American Society for Testing Materials, organized in 1899, took up the consideration of rail specifications and is still giving attention to that subject through its established procedure of investigations by committees. In 1900, the American Maintenance of. Way Association was organ-

Jan 1, 1920