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By Clarence E. Sims, Donald W. Williams, George A. Moore

INTRODUCTION DURING the past several years, the steel casting industry has made studies of heavy castings in which the test bar has been taken from heavy sections rather than from attached or separately cast coupons. It has been noted that the ductility properties of these heavy sections are often lower than those normally expected. Such lowered ductility is usually accompanied by a spotty test bar fracture, and the ductility values can often be greatly improved if a low-temperature aging treatment is given to the casting. A loss of ductility of this type is considered "abnormal," since it is not accompanied by an increase of tensile strength or hardness, and "temporary" when the ductility can be restored by aging. The cure of such an abnormal condition represents a real improvement in the quality of the steel, Several types of abnormal loss of ductility can be distinguished, of which those caused by excessive amounts of inclusions of undesirable type and those caused by unsuitable grain size and ingot structure are well known. The particular type of abnormal lowered ductility currently under consideration may be distinguished by the fact that the low-temperature aging treatment necessary for its relief is insufficient to cause any visible change in the microstructure as ordinarily observed. As this aging will in fact eventually occur at room temperature, the phenomenon of present interest may be given the symptomatic definition, "Temporary Abnormal Low Ductility." Some hundreds of previous investigations, largely qualitative in nature, have established, beyond reasonable doubt, that hydrogen is normally present in newly manufactured steel and that this gas, in small amounts, can cause a temporary abnormal loss of ductility. The commonly observed association of high gas content and low ductility has given strong evidence for the presumption that hydrogen-, possibly assisted by other gases, is the primary cause of the low ductility observed. Accordingly, The Steel Founders' Society of America has, since Nov. 1, 1944, sponsored investigations at Battelle Memorial Institute whose primary objective is to obtain quantitative information on the relation of the amount of hydrogen and nitrogen in steel, together with associated methods of steelmaking and treatment, to low-ductility effects and porosity. The interest of this investigation thus extends to permanent abnormal losses of ductility, such as are caused by the inclusions which sometimes result from special deoxidizing practices and possibly from metallic nitrides, but as these can be distinguished from the temporary effect of hydrogen, they have been excluded from the work reported here except when they

Jan 1, 1948

By Wallace Thorneycroft

FOREWORD This paper by Mr. Thorneycroft, Past President of the Institution of Mining Engineers (Great Britain), and chairman of its Subsidence Committee, is a valuable contribution to the assemblage of data on ground movement and subsidence from coal mining. It deals with the effects of advancing longwall, a method almost universal in Europe but as vet little used in the United States outside of Northern Illinois and in a few scattered places elsewhere, in thin coal beds, as in the Lexington field, Missouri, Canon City field, Colorado, and the Birmingham field, Alabama. Although by advancing- longwall, a maximum recovery of coal is obtained and it has to be employed where there are weak shale roofs, especially in deep mines, it is a more expensive method of operation unless the mining conditions are favorable, which is unusual in the United States. On the other hand, there is a growing use in this country of what is essentially retreating long wall, with an approximately straight break-line as described by Rayburn.1 With this method, in which the pillars are substantial, it was shown that the ground movement effect is practically identical with that of advancing longwall, hence the value to mining engineers of the precise data given by Mr. Thorneycroft. His study is unusual in several respects; it deals with conditions connected with ,the mining of a coal bed 20 in. thick, about 490 ft. below the surface, over a mined-out area in a 5-ft. bed about 90 ft. below, which had been mined about 12 years earlier. Both mines passed under Plean House, a building of massive cut stone construction built over a century ago, in which Mr: Thorneycroft resided throughout the under-mining period. Slight cracks opened in the walls as the longwall face approached the house in mining the upper seam, and closed after the face passed and subsidence took place. In the northwest wall, the last wall the face passed under, some stone blocks were broken, which was attributed to a strike period when the advance of face came nearly to a standstill. Other than this there was no perceptible permanent damage, as indicated by the photographs taken by the undersigned in 1923 (Figs. 1 and 2). Mr. Thorneycroft used a novel means of studying the successive positions of the corners of the building: he hung plumb bobs from the eaves and traced the paths of the respective plumb bob points on level surfaces. The angles made by the house walls with the plumb bob lines gave measures of the slope of the subsidence wave at the respective points. A slight upward wave was indicated by the surveys ahead of the subsidence, which would appear to be due to a tilting over of the massive sandstone stratum in the roof measures near the surface, the edge of the subsidence area acting as the fulcrum.

Jan 1, 1931

By Andrew B. Crichton

The oft repeated statements of the United States Geological Survey and the Bureau of Mines that the coal reserves in the United States are sufficient for 3000 yr have given us all a sense of security hard to disturb. If we discount that statement 66 pct, which to the uninformed seems drastic, we would still have 1000 yr supply, and why should mortal man worry about the difference between 1000 and 3000 yr supply of coal. That is exactly the attitude which many who should be better informed have taken toward the problem. A recent brochure "How Strong is America," by the New York Herald Tribune, states there is "no end to coal * * The truth is staggering * * U. S. has enough coal to last 4000 years." What the statement actually means is that the calculator got as high as 4000 yr and decided it was pointless to go on. The President's ERP Committee on Natural Resources and others in high places continue to assure the country of our superabundance of coal. In the past few days the "Wall Street Journal" carried an item from Director Boyd of the Bureau of Mines saying that within a hundred years we would need to triple our annual coal production of 600,000,000 tons, making it 1,800,000,000 tons annually, and at that rate we had coal reserves sufficient for 1000 yr. In my humble opinion, we cannot now or ever produce 1,800,000,000 tons annually, because we do not have the reserves in the producing districts to do it. Past reckoning in geology may be, as in the Psalms, a thousand years are as yesterday, but the future must be considered more realistically, and " a thousand years" is really a "heck" of a long time. In most developed areas, mining engineers can count the coal reserves in terms of a hundred years or less, and in some important areas now producing large annual tonnages in much under fifty years. They think when they hear of thousands of years coal reserves, reference is made to distant fields and "the fields are always green far away." The estimates of our coal reserves upon which we are relying were made in 1907 under the direction of Marius R. Campbell, Director of the United States Geological Survey. It is apparent this work was not well done. It was necessarily based on rather meager data because of the little development and prospecting as of that date. There were mistakes in the correlation of seams, and they assumed the continuity of thick seams throughout large coal bearing areas where coal often did not exist. The overstatement of coal bearing areas in the Campbell figures are common. The 1907 survey includes all coals over 14 in. in thickness to a depth of 3000 it. The total coal reserves according to Campbell were 3157.2 billion tons. The production and mining losses that year would amount to 570 million tons and

Jan 1, 1949

By William E. Ford, Edward Salisbury Dana

1. Normal Class (28) Gypsum Type 2. Hemimorphic Class (29) Tartaric Acid Type 3. Clinohedral Class (30) Clinohedrite Type Mathematical Relations of the Monoclinic System Crystallographic Axes. - The monoetinic system includes all the forms which are referred to three unequal axes, having one of their axial inclinations oblique. The axes are designated as follows : the inclined or clino-axis is a; the ortho-axis is b, the vertical axis is c. The acute angle between the axes a and c is represented by the letter 0; the angles between a and b and b and c are right angles. See Fig. 331.

Jan 1, 1922

By Paul A. Farrar, Harold Margolin

The system Ti-Cr has been re investigated From 40 to 100 pct Cr. The high-temperature modification of TiCr, was found to exist in the temperature range from 1365 where it terminates in the eutectoid reaction TiCr,(TI)* — HE chromium-rich region of the Ti-Cr system was investigated by Vogel and Wenderott,' Mc Quillan,' Van Thyne et dl.,' and Cuff Duwez and Taylor determined the crystal structure of the low-temeperature modification of TiCr, to be fcc a = 6.943A and Levinger' discovered the existence of a second (high-temperature) modification of TiCr, and determited its crystal structure to be hexagonal a = 4.932A, c/a = 1.617i. No information was obtained as to the temperature range over which each modification of TiCr? existed; therefore the present investigation was initiated. I) Experimental Techniques Alloys employed for the delination of this system were prepared from iodide titanium and high-purity chromium. The purity of these materials is as follows: Iodide titanium: purity 99.99 pct; major impurities—carbon 0.0001 pct; oxygen 0 to 0.002 pct; nitrogen 0 to 0.002 pct; silicon 0 to 0.005 pct; manganese 0.001 pct; copper 0.001 pct (Foote Mineral Co., Lot 609-29). Chromium #1: metallic purity 99.997 min.; interstitial content—oxygen 0.27 to 0.46 pct; hydrogen 0.028 to 0.038 pct; nitrogen 0.0002 pct (Ave-quipo Inc.). Chromium #2: purity 99.9 pct; major impurities—carbon 0.01 pct; oxygen 0.013 pct; nitrogen 0.02 pct; silicon 0.01 pct; sulfur 0.03 pct; iron 0.01 pct (Fulmer Research Institute Ltd.). A total of sixteen alloys of thirteen different compositions was prepared in the range from 40 to 95' *All percentages are given in weight percent. pct Cr. The compositions of the alloys prepared were as follows: Ti-40, 45, 50, 60, 62, 64, 66, 68, 70, 80, 85, 90, and 95 pct Cr. Two buttons were prepared of the 66, 90, and 95 pct Cr alloys. The 40 pct Cr and one of the 66 pct Cr alloys were prepared from the chromium # 2. All the other alloys were prepared from chromium #1. The alloys were arc-melted as 25-g buttons in a copper-hearth glass-walled furnace7 under an inert atmosphere of high-purity helium. The alloys were sintered at 250 amp and melted twice at 350 amp for 30 sec with the buttons being turned over between melts. Weight losses during melting were determined and in the range 45 to 68 pct Cr they were found, in all cases, to be less than 1.25 pct of the total alloy weight. A number of the high-chromium alloys shattered during cooling from either the first or second melt, which made the weight loss considerably larger than usual. The 70 and 80 pct alloys lost approximately 5.7 pct of their total weight, the 85 pct alloys 1.5 pct, the 90 pct alloy 2 pct, and the 95 pct alloy 3 pct. However, it is felt that the actual composition of the alloys in this region is probably within approximately 1 pct of the intended composition, as a large portion of the material lost was that due to shattering after melting. Nominal compositions were therefore used in plotting data and referring to the alloys. The alloys were cut into specimens, wrapped in molybdenum sheet, and encapsuled in argon-filled quartz or Vycor tubes for heat treatment. The heat-treatment times and temperatures are given in Table I. The specimens were quenched in iced brine (I.B.Q.) following heat treatment. The standard techniques of grinding, polishing., and etching were used in preparing the specimens for metallo-graphic examination. For alloys below 68 pct Cr

Jan 1, 1963

[NORTH AMERICA UNITED STATES Alabama BIRMINGHAM BURROWS, WILLIAM C. CORD, RICHARD H. COSTON, OTIS D. JR. FAIRHOPE RUFFLES, WILLIAM R. HUNTSVILLE WAGGONER, JERRY B. MOBILE PETROUTSON, PETER C. SELMA JONES, JAMES J. JR. UNIVERSITY CUDWORTH, JAMES R. JONES, WALTER B. RICHARDS, EDWARD F.]

Jan 1, 1961

By David L. Pentz

ABSTRACT A critical summary is given of the analytical procedures available to the engineer for the analysis of slope stability. The emphasis is on the various types of behaviour that have been measured in different rock types. A method of assessing the possibility of failure of simple three dimensional wedges is provided in an attempt to demonstrate how structural features can be included in a meaningful manner. An outline for theoretical design is provided that stresses the importance of carrying out a 'Back Analysis' of large and small instrumented failures so that realistic parameters of the rock mass forming the pit slopes can be obtained.

Jan 1, 1971

By C. C. McDermond, Others, B. N. Zavoico

Production of crude oil in Venezuela for the year 1937 was 186,653,-916 bbl., as compared with 155,228,982 bbl. produced in 1936, an increase of almost 31,500,000 bbl. The oil-field strike, which started on Dec. 14, 1936, lasted until Jan. 25, 1937, when a total of 10,000,000 bbl. of production was estimated to have been lost (5,750,000 bbl. in 1936 and the remainder in 1937). Of the total of 186,653,916 bbl. produced in 1937, the Lagunillas field contributed 45.6 per cent, a drop of approximately 10 per cent under 1936 figures; Tia Juana, 14.3 per cent; Quiriquire field, 14.0 per cent; La Rosa area, 13.3 per cent and the Mene Grande field, 7.6 per cent, these being the five leading contributors of the year's production. Detailed production figures by fields and by companies are shown on Table 1. Of the total production of Venezuela the following four major companies accounted for the greater proportion: Standard of Venezuela and Lago Petroleum Corporation together, 48.3 per cent; Shell, 37.4 per cent and Venezuela Gulf, 14.0 per cent. At the end of the year, 2491 wells were producing, of which number 1291 wells were pumpers, or about 52 per cent. Production The accompanying statistics of production record of Venezuela oil fields from its inception to Dec. 31, 1937, shown on Table 2, indicates that the cumulative production reached 1,503,283,228 bbl. In order of importance, Lagunillas leads all the fields, having accounted for about 50 per cent of Venezuelan production, followed by La Rosa area, which produced about 21 per cent; Mene Grande, which produced about 13 per cent, and Quiriquire, which produced 6.5 per cent. Table 3 shows the age of each field. Mene Grande is the oldest, having produced for 24 years; Tarra is next, 21 1/2 years old, and El Mene third, 171/2 years. The gravity of the crude from the various fields, also shown on Table 3, remained unchanged, the only addition being the new Tia Juana field, which averages 15.6' A.P.I. Table 4 shows the method of production by fields as of Jan. 1, 1938; at the end of the year 2491 wells were producing, compared with 2005 wells producing at the beginning of 1937, or an increase of 486 wells. The completions for the year reached 512. Of the 2491 wells producing crude oil, 1291 wells, or approximately 52 per cent, were pumping, 925 (approximately 37 per cent) were flowing naturally and 275 (11 per cent) were on

Jan 1, 1938

By L. Himmel, R. F. Mehl, C. E. Birchenall

The rates of self-diffusion of iron in artifically prepared wustites of various compositions have been determined using the decrease in surface activity technique. Similar measurements are reported for artificial magnetites of nearly stoichiometric composition and for natural hematite single crystals. These data, together with appropriate thermodynamic data derived from the present study or from the literature, are used to calculate the rates of oxidation of iron and its oxides, taking as a basis the theoretical rate equations developed by Wagner. The calculations are compared with experimental rate constant data for these same reactions and are shown to provide essential confirmation for the Wagner theory. For the most part, the results are also consistent with the previously proposed transport mechanisms in the oxides of iron. WHEN a metal is exposed to an oxidizing atmosphere at elevated temperatures, a superficial oxide layer is formed which then thickens according to some characteristic rate law. Provided that the oxide layer is dense and continuous and does not present any paths for gaseous diffusion, continued growth must inevitably involve the migration of the reactants—either the metal or oxygen or both—through the lattice of the solid oxide. This is true whether the reaction rate is controlled by the diffusion process itself or by a slow step in a reaction at one of the interfaces. If the overall rate is limited by diffusion, and if the concentrations or thermodynamic activities of the reactants at the boundaries of the oxide layer are independent of time, the familiar parabolic rate law is observed. Under these conditions, Wagner1 has shown that the rate constant may be expressed in terms of the mobilities of the reacting components and the appropriate concentration or activity gradients which are established across the growing oxide layer. In presenting the phenomenological basis for the theory, Wagner has emphasized the role played by lattice defects in diffusion processes in oxides. The essential validity of this theory has been confirmed by experiment for a number of simple systems including the growth of Cu2O on copper.'-' One of the objectives of the present study has been to extend the Wagner approach to the more complex process of the oxidation of iron and its oxides, and particularly to wustite, which is normally the major constituent of the oxide scales formed on iron at temperatures above approximately 570°C. For this purpose the rates of self-diffusion of iron in w?stite, magnetite, and hematite have been measured by tracer techniques and the necessary thermodynamic data have been obtained from equilibrium studies involving the oxides and their atmospheres. These data have subsequently been used to test the underlying assumptions of the Wagner theory as well as the detailed mechanism of the scaling of iron previously proposed by Davies, Simnad, and Birchenall.5 Lengthy treatments of diffusion and conduction phenomena in ionic crystals have been published." * The latest, by Jost,8 also summarizes much of the existing experimental data. In general, however, the oxides of iron have not been considered specifically and hence a brief review of the available

Jan 1, 1954

By J. R. Kyte, L. A. Rapoport, R. J. Stanclift, S. C. Stephan

Experimental studies covering a wide range of core materials and fluid properties have been conducted to determine the mechanism of oil displacement by water in a partially gas-saturated porous medium. In all instances, the presence of a gas phase was found to have a beneficial effect in reducing residual oil saturations. The practical significance of this benefit is discussed, and a simplified procedure is outlined for evaluating the effects of free gas on water flooding by means of short core tests. INTRODUCTION In addition to oil and water, reservoirs subjected to water flooding frequently contain, also, a gas phase. Common engineering procedures account for the presence of this "free gas" only from the viewpoint of volumetric balance, implying that the only role of the gas consists of providing "fill up" space. It is usually visualized that during the initial stages of the water invasion, the oil, moving ahead of the water, displaces part of the gas and that subsequently the remaining portion of the gas phase is totally compressed and dissolved in the advancing oil bank. Thus, consideration of a two-phase, water-oil flooding mechanism supplies an adequate basis for predictions of oil recovery if the pressure build-up caused by the flood is sufficiently great, so as to reduce the free gas saturation to a negligible value in any portion of the reservoir by the time that portion is reached by the advancing flood water. In many in- stances, however, waterflooding operations are carried out when the reservoir pressure is still relatively high SO that the pressure build-up associated with the water flood may not result in complete dissipation of the gas phase. Under such circumstances it is necessary to ascertain whether or not the presence of free gas has an effect on waterflood behavior and, if so, to account for any such effect in the evaluation of field operations. The difficulties encountered in attempting to arrive at a comprehensive picture of the displacement mechanism of oil by water in the presence of free gas stem from the fact that most of the published data on this subject were obtained under conditions that were either not clearly representative of those existing in a reservoir or not sufficiently controlled to permit evaluation of the effects specifically caused by the gas phase. Some of the most precise data found in the literature were obtained in tests using a "static" gas phase created prior to each water flood by circulating oil through partly gas-saturated cores until a "trapped," residual gas saturation was established throughout the system.' Other investigations were conducted under more representative conditions where the gas phase was free to move during the water flood: but in most cases the results of these tests were obscured by auxiliary phenomena which arise from the compressibility and solubility of the gas and preclude quantitative conclusions.2,3,4 Prior to water flooding, a reservoir usually contains oil and gas, distributed in a manner in which both are free to move. Thus, the principal objective of the present studies was to determine the type of displacement mechanism occurring when water invades a porous medium containing oil and a "mobile" gas phase. Further-

Jan 1, 1957

By Dennis J. McCarthy

TAX TREATMENT OF EXPLORATION AND DEVELOPMENT EXPENSES Exploration Expenditures General Principles. Exploration expenditures are expenses incurred within the United States or the Outer Continental Shelf for the purpose of ascertaining the existence, location, extent or quality of any deposit of ore or other mineral. Section 617 of the Internal Revenue Code permits a taxpayer to elect to deduct these expenditures currently. In default of election, exploration expenditures must be capitalized and included in the basis of the mineral property for purposes of determining cost depletion. Entitlement to Deduction. In order to qualify for current deduction, exploration expenditures must be incurred prior to the commencement of the development stage, i.e., when mineral deposits are shown to exist in sufficient quantity and quality to reasonably justify commercial exploitation. Generally, expenditures for geological and geophysical investigations, reconnaissance, surveying, testpitting, trenching, drilling, driving of exploration tunnels and adits and similar types of work constitute exploration expenditures if incurred prior to the commencement of development. However, expenditures to further delineate the extent and location of an existing commercially marketable deposit are not exploration expenditures. Exploration expenditures may be incurred from within a producing mine to ascertain the existence of what appears to be a different ore deposit. Expenditures for property which is subject to an allowance for depreciation are not deductible under §617. However, depreciation properly allowable on assets used in exploration is an exploration expenditure. Election to Deduct Exploration Expenditures. The election to deduct exploration expenditures is made by deducting these expenditures in the return for the first taxable year for which such treatment is desired. The election applies to all properties of the taxpayer. Once the election is made all exploration expenditures, in the year of election and thereafter, must be deducted, unless the election is revoked with the prior consent of the Commissioner. The Tax Equity and Fiscal Responsibility Act of 1982 (TEFRA) made substantial changes in the treatment of exploration expenditures. For exploration expenses incurred after 1982 and before 1984 by a corporation, the amount currently deductible is limited to 85% of the expenditure. The remaining 15% must be capitalized and recovered over a five-year period. Although exploration costs capitalized under this provision are not part of the basis of the property for cost depletion purposes, investment credit may be claimed with respect to these expenditures. Further changes have been added by the Tax Reform Act of 1984 with respect to expenditures made after 1984. The Act reduces the amount of otherwise currently deductible costs from 85% to 80%. Additionally, it limits the availability of the investment credit for capitalized mineral exploration costs to deposits located in the United States. TEFRA also allows individuals a special method of recovery under which exploration expenditures may, at the election of the taxpayer, be amortized ratably over a 10-year period beginning with the year in which the costs are paid or incurred. If taxpayer does not use this method, the excess of the exploration expenditures actually deducted over the amount that would have been deducted if 10 year amortization had been elected is an item of tax preference subject to the alternative minimum tax.

Jan 1, 1985

By M. G. Benz, J. F. Elliott

A new type of solution calorimeter has been constructed to measure heats of mixing, enthalpy increments, and heats of fusion, formation, and reaction at temperatures above 1000°C. With it, measurements hove been made of the partial molar heats of mixing joy tin in the Cu-Sn system from 0 to 13 at. pet Sn at 1127°C and fir nickel in the Cu-Ni system from 0 to 9 at, pet Ni at 1200°C. The integral molar heat of mixing for the Cu-Sn system is strongly negative with a calculated minimum value corresponding to the composition Cu3Sn. The integrnl molar heat of mixing for the Czi-Ni system is slightly positive at these temperatures. These integral molar values have been measured with a probable error less than 30 cal per g-atom at an atom fraction of nickel or tin equal to 0.1. The estimated probable error for the Cu-Sn system is approximately 450 cal for a measured heat of solution of approximately 9000 cal. For the Cu-Ni system it is approximately 700 cal for a measured heat of' solution of approximately 60 cal. A new type of heat of solution calorimeter was designed and constructed to provide a more accurate experimental method for determining heat effects at high temperatures, (T > 1000°C). With it, partial molar heats of mixing, enthalpy increments, heats of fusion, and heats of formation and reaction for metal systems can be measured directly. Previously it has been necessary to rely upon the use of the dropping calorimeter or the van't Hoff equation applied to equilibrium data for this information. For the most part equilibrium data are scarce and difficult to obtain in many cases, and it has been necessary to rely upon the "method of mixtures" for the desired enthalpy measurements. An earlier study1 provides a prototype for this work. The "method of mixtures" as outlined by K. K. kelley,2 "consists of dropping the substance under investigation from a furnace, with controlled and measured temperature, into a calorimeter operating at or near room temperature.'' In this manner the change in the total heat content (enthalpy) of the substance between the temperature of the furnace and that of the calorimeter is determined. In order to determine high-temperature heats of mixing, enthalpy increments, and heats of fusion, formation, and reaction, it is necessary to take the difference between two such measurements, one before and one after the occurrence of the enthalpy change being studied. The desired enthalpy change is then the small difference between two large numbers. Small errors in the large numbers are included as large errors in this small difference. It is this difficulty that must be avoided for accurate measurement of the desired functions. The procedure with the new solution calorimeter consists of dropping the substance under investigation from a furnace, with controlled and measured temperature, into a solution calorimeter operating in the temperature range of 1000o to 1200°C. Measurements in the range of 1200" to 1600°C are planned for the future. By selection of the composition and

Jan 1, 1964

By A. Thies, Wm. B. Phillips

1. Introductory Remarks.—The Haile Gold Mine is in Lancaster county, South Carolina, 3 1/2 miles east of Kershaw station on the Charleston, Cincinnati and Chicago Railway. It was first opened about, the year 1832, and since that time has passed through various fortunes. Many different operations have been practiced here for extracting the gold : panning, grinding in Chilian mills or arrastras, stamping, the Designolle process, dry-crushing, and finally the Thies process of barrel-chlorination, which has now been in successful use for 2 1/2 years, and by which 36,000 tons of ore have been treated profitably. The Thies process is in brief the treatment of dead-roasted auriferous concentrates (pyrite, sometimes also chalcopyrite, as at the Phœnix mine, Cabarrus Co., N. C.) with nascent chlorine, without ' artificial pressure or exhaust, in lead-lined iron cylinders; the throw-

Jan 1, 1891

By M. F. Williams, L. G. Hendrickson

In classification of pulps bearing magnetized ferro-magnetic particles, depolarizing is of great importance. If size separation is to be effective, particles must be individual rather than in flocs. Depolarizing is also practiced in heavy medium separations in which ferrosilicon or magnetite is the medium. When particles of ferromagnetic material have been removed from a magnetic field, residual magnetism causes agglomeration. The term depolarizing refers to the operation of reducing or eliminating this residual magnetism and may thus be considered magnetic deflocculation. The terms demagnetizing and randomizing are also used.

Feb 1, 1956

By Max Y. Seaton

The scope of this paper will be limited to finished materials that contain a large preponderance (around 80 per cent or more) of magnesium oxide. The large and commercially important production of refractory dolomite and modified dolomites is not discussed here, and the production of magnesium basic carbonate for use as a heat insulator is barely mentioned. The discussion is confined mainly to magnesias produced in comparatively great quantity by direct processing of naturally occurring raw materials and hence excludes secondary or highly purified products such as pharmaceutical products or U.S.P. light and heavy calcined magnesias of commerce. Nomenclature The nomenclature of the magnesia products that will be discussed is somewhat confusing, in that it is customary in the trade to designate as "calcined magnesite" the materials that result from the calcining of magnesite to temperatures that remove the contained carbon dioxide. The finished product, therefore, is not magnesite at ali but simply a more or less pure magnesium oxide or magnesia. Furthermore, partly for statistical .and partly for commercial reasons, it has been customary, during recent years, to classify as "calcined magnesite" products that result from the heat-treatmerit of magnesium hydroxide precipitated from magnesium-containing brines; prod- ucts that, obviously, have no relationship whatever to magnesite. In the listing of magnesia-containing materials, tonnages of which are regularly reported by the Bureau of Mines, reports ordinarily are made under two headings: "caustic calcined" magnesite, in which all of the varieties of products treated at relatively low temperatures are lumped; and "dead-burned" magnesite, in which are included both high-purity and low-purity, and particularly both high-iron and irow-iron, materials that have been so heat-treated that the magnesium oxide occurs predominantly as crystalline periclase— materials used almost entirely for refractory purposes. In 1940 the apparent domestic consumption of "caustic calcined" magnesite was approximatcly 17,000 tons, "bout 95 Per cent of which was produced in this country. The apparent consumption of "dead-burned" magnesite was approximately 172,000 tons, some 82 per cent of which was domestically produced. In both total quantity and percentage of material produced within the United States, these figures are record highs for manY Years past. Utilization As indicated by these figures, the major tonnage outlet for magnesia is the refractories industry, in which magnesia is employed principally in three ways: (1) as dead-burned grain magnesite for the construction and maintenance of the hearths Or bottomS of basic open-hearth furnaces; (2) in the form of refractory magnesite bricks and shapes; and (3) as a chemical

Jan 1, 1942

By Max Y. Seaton

The scope of this paper will be limited to finished materials that contain a large preponderance (around 80 per cent or more) of magnesium oxide. The large and commercially important production of refractory dolomite and modified dolomites is not discussed here, and the production of magnesium basic carbonate for use as a heat insulator is barely mentioned. The discussion is confined mainly to magnesias produced in comparatively great quantity by direct processing of naturally occurring raw materials and hence excludes secondary or highly purified products such as pharmaceutical products or U.S.P. light and heavy calcined magnesias of commerce. Nomenclature The nomenclature of the magnesia products that will be discussed is somewhat confusing, in that it is customary in the trade to designate as "calcined magnesite" the materials that result from the calcining of magnesite to temperatures that remove the contained carbon dioxide. The finished product, therefore, is not magnesite at ali but simply a more or less pure magnesium oxide or magnesia. Furthermore, partly for statistical .and partly for commercial reasons, it has been customary, during recent years, to classify as "calcined magnesite" products that result from the heat-treatmerit of magnesium hydroxide precipitated from magnesium-containing brines; prod- ucts that, obviously, have no relationship whatever to magnesite. In the listing of magnesia-containing materials, tonnages of which are regularly reported by the Bureau of Mines, reports ordinarily are made under two headings: "caustic calcined" magnesite, in which all of the varieties of products treated at relatively low temperatures are lumped; and "dead-burned" magnesite, in which are included both high-purity and low-purity, and particularly both high-iron and irow-iron, materials that have been so heat-treated that the magnesium oxide occurs predominantly as crystalline periclase— materials used almost entirely for refractory purposes. In 1940 the apparent domestic consumption of "caustic calcined" magnesite was approximatcly 17,000 tons, "bout 95 Per cent of which was produced in this country. The apparent consumption of "dead-burned" magnesite was approximately 172,000 tons, some 82 per cent of which was domestically produced. In both total quantity and percentage of material produced within the United States, these figures are record highs for manY Years past. Utilization As indicated by these figures, the major tonnage outlet for magnesia is the refractories industry, in which magnesia is employed principally in three ways: (1) as dead-burned grain magnesite for the construction and maintenance of the hearths Or bottomS of basic open-hearth furnaces; (2) in the form of refractory magnesite bricks and shapes; and (3) as a chemical

Jan 1, 1942

By J. D. Pelletier

SAN MANUEL orebody is a disseminated copper deposit in quartz monzonite, monzonite porphyry, and diabase. Quartz monzonite, which is Pre-Cambrian1 in age, is exposed in an area including No. 1 and No. 4 shafts and extending about 2400 ft southeast from No. 1 shaft. It is also exposed in the bottom of No. 2 shaft and in a zone roughly 500 to 1200 ft southeast of No. 2 shaft having its long dimension along a northeast-southwest axis. Churn drilling has shown all these exposures to be parts of a contiguous mass of quartz monzonite lying within and beneath the ore zone.

Jan 7, 1957

By K. E. Beu

THE integrated intensity X-ray method of meas-uring retained austenite concentrations in hardened plain carbon or low alloy steels as proposed by Averbach and Cohen1,2 has the advantages of being a highly sensitive and precise quantitative method. The various phases of this method have been studied and several modifications have been developed which aid not only in reducing the time required per determination, but which also increase the possible accuracy of the method. A fundamental step in the original calculation procedure is to plot V.A(?) curves for austenite and martensite and to obtain VM/VA ratios from these curves.' In taking this ratio the absorption factor A (8) drops out since it is constant for a. given diffraction angle 8. The reason for eliminating A(?) in this manner is because it is apparently assumed

Jan 1, 1953

By Waldemar Lindgren

THE purpose of this paper is to present certain facts relating to Cordilleran differentiation and metallization. Theoretical discussions concerning the exact modus operandi of differentiation, the causes that led up to it, and the original distribution of the magmas have been omitted because the author feels that his knowledge is deficient. These subjects have been adequately treated in the admirable works of Iddings, Daly, Harker, Tyrrell, Shand, and Wolff. The facts here set forth seem to indicate that differentiation and metallization form one continuous process during the eastward movement of the magmas, culminating in the alkaline province of the eastern border of the Cordilleran Ranges.

Jan 1, 1933

By A. Sainato, E. Baker, J. Cervik

In Europe, water infusion is used widely to reduce generation of respirable dust during mining. Its use in the US is limited to a few plow operations in the deeper parts of the Pocahontas No. 3 Coalbed. The technology for infusing water into retreating longwalls is described and results of a recent Bureau test in the Lower Sunnyside Coalbed demonstrated dust reductions ranging from 47% to 64%. Because water infusion increases moisture content of the coalbed, face air velocities in excess of 2.5 m/s (500 fpm) are possible, further diluting dust levels before dust entrainment occurs. An economic analysis shows a 23% reduction in operating costs when coal production is increased by changing from unidirectional to bidirectional mining with water infusion.

Jan 1, 1986