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By J. J. Egan, A. B. Kinzel

Much work has been done recently in an attempt to analyze the physicochemical mechanism involved in the production of steel by the open-hearth process. This has resulted in reducing the process to a series of interrelated phenomena obeying the usual laws of mass action and diffusion. Of these, the reaction of the iron oxide and carbon in the molten steel is of most interest from a technical point of view as it constitutes the main action in the usual steelmaking processes. A. L. Feild' has formulated a basic differential equation expressing the open-hearth reactions and Herty has done considerable experimental work on the determination of a number of constants involved in the basic open-hearth reaction. In considering the application of the law of mass action to the reaction FeO + C + CO + Fe, the iron will be taken as constant, as is the case in the open hearth and the carbon monoxide pressure will be assumed constant at one atmosphere. From this xy = m at equilibrium, where x is the percentage weight of carbon, y percentage weight of iron oxide and m the weight-concentration equilibrium constant. While it is customary for physical chemists to express equilibrium constants in terms of molar concentrations, the constant is here expressed as the product of the percentage-weight concentrations for ease of comparison with the constants quoted by Herty and by Beild, and for more ready applicability to the open-hearth reactions. Herty and his associates have attempted to calculate the value of this constant from data on open-hearth heats. So many variables affect these results that an adequate calculation presents very great difficulties. A value of 4 X lop2 was first arrived at, but this was later changed to 1.6 X 10-2. Feild, in order-to illustrate the operation of the differential equation of the open hearth, has assumed a value considerably lower than Herty's, namely, 1.0 X 10-2, the largest value consistent with certain theoretical

Jan 1, 1929

By W. C. Lacy

Urban development in semi-arid portions of the Southwest has upset a natural balance of geological conditions resulting in broad-scale and local subsidence or heaving ground conditions, Subsidence can be traced to two general causes: irrigation of reclaimed desert lands that have dry, low-density soils; and depression of the water table by ground water withdrawal. Accumulation of weathered volcanic tuff produces areas with swelling characteristics. Soil and subsidence studies made in the Tucson area in Arizona illustrate foundation problems typical of the Southwest that must be considered in the design of building codes. Anticipation of problems and the adoption of corrective measures in the design of engineering structures, establishment of pertinent building codes, and urban planning and zoning to obtain optimum land usage and conservation of natural resources demands a thorough understanding of geological conditions of a developing urban area. In the arid to semi-arid southwestern United States erosional and depositional processes result in special situations that require special precautions in building practices. A series of studies currently underway in the Tucson area, prompted by foundation failures and breaking of buried service lines, serves to illustrate some of these relationships between the geological environment and history and engineering problems. ENVIRONMENT The desert region of the Southwest is characterized by isolated mountain ranges rising abruptly from low valleys or plains — the ranges generally occupy less area than do the intervening valleys. In southern Arizona the valley floors step up from near sea level to 2000 ft or more in elevation, and the ranges may rise to over 7000 ft. Desert and steppe-type climates predominate — climate is controlled more by elevation than it is by latitude. Both climate types are characterized by a lack of precipitation, the former more so than the latter. Practically all the rain that falls in the region evaporates; runoff or recharge generally occurs only during the wettest period. Water table levels are generally being depressed. Vegetation is restricted and consists mainly of creosote bush, cacti and sage brush on the deserts, and mesquite, pinon juniper and various types of grass on the steppes. Precipitation varies from about 3 in. on the warm deserts to about 12 in. on the steppes. Most of this falls in the summer or winter, with only rare storms in other seasons. Summer thunderstorms, often accompanied by hail, bring cloudbursts which send torrents of water streaming down the mountains onto

Jan 1, 1964

By E. H. Erwin Gartner

The Rhenish lignite deposit in the Nordrhein-Westphalia province of the German Federal Republic covers an area on the left bank of the Rhine River of about 970 sq miles (Fig. 1). Here, in the Miocene era, some 20 million years ago a lignite seam was formed and later broken, through tectonic movements into several blocks, some thrown down into depths of over 1,500 ft. This deposit consists of a single seam, in places up to 300 ft thick, but averaging about 150 ft. In a few areas, it is split into as many as five seams, separated by barren strata. It contains about 60 billion tons (2000 lb/short ton) of lignite which, however, being relatively young geologically, has, because of approximately 60% moisture, 2 to 8% ash, and low sulfur, a net calorific value of 3,340 Btu. That calorific value increases, however, with rising thickness of the cap rock. About one-third of the yearly production of 90 to 100 million tons of raw lignites is converted into briquets. Raw lignite is pulverized and dried to about 18% water content and then pressed without binder into briquets under a pressure of about 14,000 psi. The briquets are being used primarily for residential heating; their sales, however, have been declining sharply since 1963. On the other hand, the volume of raw lignite used in steam power plants has been rising steadily and amounts at present (1968) to about two-thirds of the total production. Huge steam power plants, such as Frimmersdorf, shown in Fig. 2 (which, with an installed capacity of 2,600 MW [megawatt], represents the world's largest steam power plant) with a generating capacity of up to 300 MW per unit and a total installed capacity of over 6,000 MW, contribute about 26% of the total electric power production of the German Federal Republic.

Jan 1, 1969

By Albert E. Ketler

Introduction – The introduction of computerized monitoring and control (M/c) equipment into the U.S. coal mining industry may prove to be of truly revolutionary proportions in the 801s.Many of you are aware that the British have developed and have been using such sophisticated M/C equipment for performing production and safety related tasks in their coal mines for nearly a decade. The benefits of M/C systems in the mining industry are usually separated into those which improve productivity, and hence make money for the company, and those which improve safety, and hence cost money. The economic benefits of M/C are startling for the production related functions such as for monitoring and controlling conveyor belts, de-watering pumps, electrical power distribution, and the like. It doesn't take much analysis to show that hundreds and even thousands of tons of coal don't get mined every time a belt shuts down or when power is out due to circuit breakers tripping for any number of reasons. A flood, caused by a malfunctioning pump which goes undetected for lack of feedback monitoring of pumping parameters, can destroy literally millions of dollars worth of mining equipment. The M/C system would be justified or not based on whether or not the productivity benefits balanced the cost within a timespan commensurate with the return on capital philosophy of the company. The safety related benefits are easily underestimated or ignored completely and the purpose of this paper is to under-score some of these benefits, as well as to review the application of M/C to the coal mining industry. The companies involved are Transmitton Ltd of England and Minetics Corp of Pittsburgh, Pennsylvania. Transmitton is probably the most experienced manufacturer of M/C equipment in the world having some 200 installations to its credit. Minetics is the marketing and manufacturing arm for Transmitton in the U.S.A. and is responsible for all aspects of distribution and service. Plans are underway for manufacturing of the Transmitton hardware for U.S. sales to be transplanted into U.S. subcontractors by 1981. Thus our coal mining industry will benefit from British technology, but without the delays and additional costs usually involved in international shipments.

Jan 1, 1981

By C. R. Hayward

THE CHAIRMAN (ALBERT SAUVEUR, Boston, Mass.).-I am sure we are indebted to Prof: Hayward for his addition to our knowledge of the influence of sulphur on steel. As he has said in this paper, sulphur has had many defenders in recent years. It seems to me, however, that, while it may be old school to believe in the detrimental action of sulphur, it is not yet old school to believe in segregation; that while it may be that 0.1 per cent. of sulphur has no very great effect on the physical properties of steel, a ladle analysis of 0.1 per cent. of sulphur may readily result in 0.2 or 0.3 per cent. sulphur being present in the segregated portion of the ingot, and that, it seems to me, might be a rather serious matter. J. S. UNGER, Pittsburgh, Pa.-Prof. Hayward has presented the results of an investigation along a line to which I have devoted considerable time and attention, and I am particularly pleased to note that his results are in accord with my own and further tend to prove the fact that the old, established prejudice against sulphur is based more on belief than actual facts. I have felt for years that tooo much stress was placed on the harmful influence of certain elements in steel such as sulphur, phosphorus, copper, etc., but it has only been within recent years that efforts have been made to, establish the truth. Practically all the investigations made to date have proven that these elements within reasonable limits are harmless and, in fact, that for certain purposes the addition of these elements is beneficial. In referring to copper, J. E. Stead, Vice-President of the British Iron and Steel Institute, said at their last meeting: "Even today one comes across steel specifications in which copper is barred, which can only be regarded as ail indication of ignorance, if not stupidity, of those who prescribe the composition of steel, for it has been long ago proved that copper in steel, instead of being an evil, is quite harmless, and is sometimes distinctly beneficial." Sulphur owes its evil name to the early days of the manufacture of steel. Chemical analyses were crude, and failure due to either poor raw materials or metallurgical treatment were many. Sulphur being a comparatively easy element to determine with reasonable accuracy, particular attention was called to the amount of sulphur, and the failure was attributed to it, without giving any consideration to other causes. A pre-

Jan 4, 1917

By A. L. Blomfield, M. J. Trott

ThE Golden Cycle Mining and Reduction Co. operates its custom mill at Colorado Springs on Cripple Creek ores exclusively. These ores are straight sulfo-tellurides, with practically no base metals such as Pb, CU, Zn, As, or Sb. Upon entering the mill, the ore all passes through the sampler to storage bins, where beds of 5000 tons each are made to insure uniformity in roasting. Classification of ORes For efficiency, it has been found advisable to separate the ores into two classes according to their lime content. Other constituents have their effect, such as alumina and magnesia, but, speaking generally, these are roughly proportional to the lime, which, as CaO, is used as the indicator. Class A contains not more than 2 per cent. CaO and comprises about 66 per cent. of the ore treated. Class B contains over 2 per cent. CaO, and comprises 34 per cent. of the ore treated. Typical analyses of both classes are as follows: Class A a B Insol.......................... 86.70 75.90 Al2O3........................:.. 2.30 3.40 Fe.............................. 3.26 3.48 CaO............................. 1.57 5.12 S............................... 1.79 1.80 MgO........................... 0.21 1.08 Ignition loss..................... 3.20 6.50 99.03 97.28 The beds of each class of ore are made as large as possible with the available ore as it comes in, to avoid changing from one bed to the other any oftener than necessary. Each roaster will handle 50 per cent. more of class A ore than of class B, with practically the same results. This necessitates changing the rate of feed for each new bed and tends toward a poor roast and loss of tonnage at each change.

Jan 1, 1919

By A. S. Adams

A GLANCE at the list of papers1 that have been published since 1920 on the general subject of flotation suggests the variety of ideas that exist regarding the underlying cause of the phenomenon.' Among these ideas, we find several coherent theories, but none that adequately and completely explain the phenomenon. Ralston2 and Bains3 suggested an electrical theory which has to do with the attachment of mineral particles to a bubble by the attraction of unlike electrical charges. This theory has its root in the fact that a bubble of air in pure water is electrified in such a way that the surface is negatively charged while the body of the water is positively charged. This result, which was first discussed by Helmholtz, also obtains when the water contains anything except a high concentration of hydrogen ions, or ions which are trivalent or tetravalent. The theory also holds that the mineral particles have positive charges on their surfaces, and so there is attachment between bubble surface and mineral particles by the old law of electrostatics, which states that unlike charges attract. CONTACT ANGLE AND OIL ATTRACTION The contact angle-the angle formed by a fluid-fluid boundary when both are in contact with a solid-has been indicted several times for complicity in the phenomenon of flotation. This angle is supposed to indirectly measure the surface energy of a solid. Thus if we have two fluids in contact with a solid, we may express the difference between the two fluid-solid tensions as equal to the fluid-fluid tension times the cosine of the angle between the two fluids.4 If the two fluids are in contact with the solid, this is, no doubt, an excellent way of establishing relative surface energies. However, in flotation, we deal with substances which are not wetted by water. What assurance have we, then, that the angle

Jan 1, 1928

Map

Jan 1, 1960

By Irnack C. Do Amaral, Mark C. Malamphy, Desio S. Oddone

Most igneous rocks, and particularly those of the basic type, contain relatively high percentages of magnetite and other iron oxides, which give them moderately high magnetic susceptibilities and make them responsible for an important percentage of the magnetic anomalies observed during the course of geophysical surveys by the magnetic method. The irregular form and high susceptibility of the igneous rocks make them readily polarizable and the position and strength of the magnetic poles formed are not always explicable by theoretical calculations of anomalies due to certain assumed forms in the normal magnetic field of the area under study. During the last four years our field work has permitted us to make detailed observations of anomalies due to igneous rocks in all the states of south Brazil. The form and position of the igneous rock at some places were fairly accurately known, which made it possible to calculate theoretical anomalies and compare them with the observed data. Some of the data we obtained have been published and additional cases are now awaiting publication. In this paper, we will present a few specific cases where the geology is moderately well known and which we believe to be of considerable value as representing typical magnetic anomalies in the south magnetic hemisphere, where the inclination of the magnetic field is very low. Although the vertical intensity is negative in the Southern Hemisphere, we have adopted the convention of plotting increase in intensity (negative) as a positive anomaly; i.e., above the x axis. This convention facilitates comparison with anomalies in the north.

Jan 1, 1940

By W. A. Thomas

Steam is, and doubtless always will be, the basic power in the anthracite industry, either directly applied through engines and pumps or electrically. The rapidity with which electric power is being applied to the mining and preparation of anthracite leaves little doubt as to its utility and economy. There is practically no operation, except possibly the drilling of hard rock, that has not been successfully electrified and the matter of drilling is handled economically with electrically driven compressors and the standard compressed-air drills. Conservation and the seemingly ever-increasing cost of production, justify careful consideration of the possible results of the more extensive use of electric power in the industry. It is not planned to discuss, herein, the relative economies of individual applications but to consider the relative economy and flexibility of steam and electric power. The reports available for the year 1920 indicate a production of slightly over 80,000,000 tons of anthracite, of which 8,843,500 tons were used for power and heating purposes; in other words, over 11 per cent. of the production was used at the mines. Some of this was used to generate electric power at the mines, about 160,000,000 kw-hr., while 150,000,000 kw.-hr. was purchased from the public utility companies. One large producer, who is buying some electric power and generating some, used over 13 per cent. of the production for power and heating at the mines. Another producer, where considerable electric power is generated on the properties, is using less than 9 per cent. of the output for power and heating. One of the largest producers has a fuel consumption of over 15 per cent. of the output, besides which considerable power is purchased. A careful study of the field indicates that steam-operated plants use upwards of 13 per cent. of the production for power and heating, while electrically operated plants use about 1 per cent. for heating; so that, for steam-power purposes at least 12 per cent., or 268.8 Ib., are used for power out of each ton produced. In the complete electrification of anthracite mining operations, no set rule can be given for the power requirement, in kilowatt-hours per ton, as conditions vary widely in the matter of pumping, ventilation, and transportation, but the following cases are given as a basis of determining a range and a possible average power requirements:

Jan 1, 1922

By Philip Wilson

Tun mines of the Calumet & Arizona Mining Co. are situated in the Warren Mining District, Cochise County, Arizona, between Bisbee and Warren and adjoin those of the Copper Queen Consolidated Mining Co. and the Shattuck Arizona Copper Co. Paleozoic limestones of considerable thickness have been intruded by granite porphyry. A great stock of the intrusive outcrops boldly near the city of Bisbee and is known as Sacramento Hill. From this central core the porphyry has tongued out into the limestone for many thousands of feet as dikes and sills of irregular shape and variable dimensions. Churn drilling has recently developed a large tonnage of secondarily enriched copper ore in the main porphyry mass of Sacramento Hill. While some ore has been found in porphyry in other parts of the district it is relatively unimportant compared with that which occurs in the Paleozoic limestone as irregular lenses replacing favorable beds near porphyry contacts or associated with well-marked fracture zones often many hundreds of feet away from the intrusive. In a zone extending from Sacramento Hill for a distance of from 1,500 to 3,000 ft. the limestone has been extensively metamorphosed and in this contact metamorphic zone the ore occurs through a known vertical thickness of upward of 900 ft. and individual orebodies often show extension in a vertical direction of over 200 ft. At a greater distance from the intrusive stock the ore occurs as lenses of greater horizontal than vertical dimensions with an average thickness of approximately 30 ft. An exception to this rule is found in the occasional steeply dipping mineralized fractures, almost true tabular veins, which are found long distances away from the zone of contact metamorphism.

Jan 7, 1916

By F. W. McQuiston, L. J. Bechaud

3.2-1. Introduction. Much has appeared in the technical literature on theory of sampling (18, 37), weight of sample required in relation to particle size (28), probability of error in sampling (3), and statistical analysis of sample data (20). Each industry, whether it be copper, iron ore, or coal, has its own standards and methods. All of the rather extensive theoretical treatments appearing in published literature on sampling apply to material already on hand such as coal, iron ore, or copper concentrates in rail cars, or in moving streams such as on conveyor belts. The attempt usually is to apply statistical techniques in order to improve reliability and precision in sampling, and to reduce differences between the analyses of seller and buyer. In contrast to this type of sampling, very little has appeared in the literature on sampling a virgin deposit from the metallurgical point of view. Perhaps it would he more descriptive to designate this point of view as "Gm-metallurgical," since geology is inextricably interwoven with metallurgy in gaining an understanding of the complexities of a deposit, eventually leading to a definition of mineable reserves, with the development of a flowsheet and engineering criteria for the planning of a successful and profitable operation. The degree of cooperation between these two departments often determines whether the processing plant is a success at the inception of operations, or whether expensive changes and modifications must he made, with the plant finally reaching rated capacity at some later date. The first concern of the metallurgical department should be to establish proper accreditation of the samples which will be used in any ore-testing campaign. It should he made mandatory, as part of operating management policy, for the responsible metallurgist to he aware of the significance of the samples and to become intimately knowledgeable in all aspects of metallurgical behavior and response to treatment of all varieties of ore in the deposit under consideration.

Jan 1, 1968

By John V. Beall, John Cameron Fox

Organization In 1948, the Committee on Divisionalization and Publication Program of AIME, known as the Johnson Committee, recommended the reorganization of the Institute into three branches, Mining, Metals and Petroleum. This recommendation was accepted and the new organizational structure was implemented in Jan., 1949. The Mining Branch, at the time of the formation, had three divisions: the Coal Division formed in 1929, the Industrial Minerals Division (IndMD) dating from 1935, and the Minerals Beneficiation Division (MBD) formed in 1948 from the Milling Methods Committee, which had existed for many years. There did not exist, however, a division for the geologists and mining engineers. From the time of the founding of the Institute, this group was the main stem of AIME and never felt the need to segregate. The disciplines of mining and geology were served by a number of technical standing committees of AIME. With the birth of the new Branch, a new Division, the Mining, Geology and Geophysics Division (MGGD) was formed, completing the divisional structure of the Mining Branch and providing a home for all members. The governing body was the Mining Branch Council, with two members from each Division of the Mining Branch and one each from the Mineral Industry Education Division and the Mineral Economics Division. These last two divisions served all three Branches of AIME. The Division is such an important unit in the organization structure that it is of value to explain that it appoints committees to handle pro- grams, publications, and awards - representing the main functions of the Institute - as well as many others. There is enough flexibility in the organization so that each Division may have its own special committee structure as long as primary functions are provided. The past is indeed prologue to the future, for in 1957 the Johnson "Branches" gave way to the Fletcher "Societies." The Fletcher Committee, in 1958, recommended a new reorganization into Societies, each with the authority to administer its own finances and to designate certain officers and directors to the AIME Board. The date on which the Society of Mining Engineers was formed in Feb., 1957, has become known as "R" Day. A smooth transition from the loose Branch structure to Society organiza-

Jan 1, 1971

By Alan Morris

The investigation of the hot-working properties of metals and alloys furnishes a problem which has been attacked in many ways. Tensile, impact and hardness tests on heated specimens have furnished interesting data, but in most cases either the tests are difficult to make or the results hard to translate into terms of practical value. Some investigators have used the drop hammer to advantage. It furnishes a rapid and simple method of comparing the plasticity of metals at elevated temperatures. The indications obtained by its use are of value only in so far as their significance is understood and they can be intelligently used to predict the behavior of a given metal under given hot-working conditions. The work reported here was undertaken not only to add something to the existing volume of such data but also to contribute to our understanding of the results. Doerinckel and Trockels1 used cylindrical specimens and determined the work required to reduce the specimen to one-half the original height. Ellis2 studied the effect of constitution on the malleability of steel at high temperature. His method and that of Kent3 were similar to the one used in the present work. The tests described by Kent were made on samples of tin, zinc, aluminum, copper, lead, 70:30 and 60:40 brasses, with and without a small quantity of lead. He concluded that the test would "indicate whether a material can be forged at a given temperature without cracking." This interpretation must be used with caution. While it is probably true within limits, one must consider the severity of the forging operation. Again, it will not apply strictly to forms of hot working other than forging. For instance, an alloy running 61.0 per cent. copper, 3.25 per cent. lead, remainder zinc, will crack badly in the test, yet, it is extruded commercially. When the possibility of hot-working a new alloy is being considered a study of its drop-hammer test should help

Jan 1, 1931

By W. A. West

ONE who attempts to collect and classify equilibrium data from various iron-alloy systems is soon struck with the absence of any quantitative theory that can serve as a general background against which to compare and contrast results from different systems, at different temperatures, and with different concentrations. It is not necessary to wait for a perfect theory; investigation of divergences of theory from observation may prove of great value in acquiring understanding of the subject. For example, one has only to think of Raoult's law as applied to aqueous solutions. The equations developed by Zener1 represent an effort to provide such a quantitative theoretical background, and it is therefore desirable to subject this theory to such tests as can be applied. The present article is intended to be an application of available tests, and may thus be considered as a supplement to Zener's paper. It is assumed that this paper is available to the reader. The equations make it possible to calculate the effect on the equilibrium concentration of one alloying element due to the presence of one or more other elements. In particular they are intended to give, for alloy steels, the carbon concentrations in alpha and gamma phases in equilibrium with each other, and in gamma in equilibrium with cementite. They may, however, be modified for use for carbon-free alloys. A summary is given later of the equations used in analyzing the data in this paper, and the symbols are there defined. About 125 papers have been examined for experimental data suitable for this investigation. An effort was made to look up all available reports of ternary systems including iron and carbon, as well as similar systems of higher order. Supplementary material was also obtained from a number of binary systems. A few noncarbon ternary systems were also found to which these methods could be applied. A comparatively small proportion of the papers read provided usable material. In many systems the number of quantitative observations made in the iron-rich region is extremely small, and the smoothed curves to be found in most published phase diagrams are entirely useless for quantitative treatment. This opinion is confirmed by the authors of the series on Alloys of Iron Research, whose remarks show clearly that they have no illusions as to the accuracy of many diagrams that they present. A further difficulty arises from the fact that these equations apply only to rather low percentages of alloying elements. The result is that at the lowest concentrations, where the best agreement might be hoped for, the errors of observation become relatively very large. The experimental difficulties in measurements of this kind of equilibrium are, of course, an old story.

Jan 1, 1946

By N. V. Hansell

The last few years have shown an increasing interest in the subject of beneficiating iron-ores in all iron-producing countries. In the United States, this movement has been slower than in certain parts of Europe, for the obvious reason that the abundance and relative cheapness of the Lake Superior irou-ores has hindered the development of enterprises for the preparation of low-grade ores. Gradually, however, conditions have changed. The world's consumption of iron is increasing enormously. Being in 1900 about 40,000,000 tons, in 1910 it was already 60,000,000; and there is no reason to doubt that for the near future the increase in iron-cousumption mill continue at the same rapid rate, especially with the development of China, certain parts of Africa, and other regions which have hardly been touched as yet by modern industrialism. It is, therefore, not surprising that apprehension is felt that the known available iron-ore resources of the world are gradually being depleted. Signs of this feeling are the recent iuvestigation, under the direction of the U. S. Geological Survey, of the iron-ore resources of the United States, and the estimate presented to the last International Geological Congress, at Stockholm, Sweden, of the iron-ore resources of the world. These investigations have emphasized the fact that the known high-grade ore-deposits are limited in extent, and will, at a not distant future, be exhausted, compelling the iron industry to depend for raw material on the enormous deposits of low-gratle ores which are distributed over almost all the world. The discovery of new deposits of high-grade ore, in countries not yet thoroughly explored, will not materially change this prospect. Of course, the part which such new deposits will play in the future cannot be forecast. The difficulty and cost of transportation will probably exclude many of them from use at the present centers of the iron industry.

Jan 1, 1913

By A. F. Taggart, F. E. Beach

The flotation process for the concentration of ores is a method by means of which one or more of the minerals in the ore (usually the valuable ones) are picked up by means of a liquid film and floated at the surface of a mass of fluid pulp. Here they are separated from the other minerals, which remain immersed in the body of the pulp. In general, the minerals which are floated are sulphides of metallic luster, but some other minerals of metallic luster such as graphite and some sulphides with adamantine luster, such as sphalerite and cinnabar, are amenable to treatment by the process. The importance of flotation lies in the fact that it is primarily a "slimes process" by means of which the particles of valuable mineral, too fine for efficient gravity concentration, are saved with a high percentage of recovery. Recoveries in the mills treating low-grade copper sulphide ores have been advanced 10 to 20 per cent. by the installation of the process and similar increased savings have been accomplished by the same means in mills treating sulphide ores of zinc and lead. When finely ground ore containing sulphides mixed with a siliceous or earthy gangue is brought gently onto the surface of a body of water, in a direction forming an acute angle with the surface of the water, a considerable portion of the sulphide constituent of the ore floats on the surface of the liquid, while the gangue sinks. This is the so-called film flotation, exemplified by the Wood and Macquisten processes. When gas bubbles are introduced into a fluid pulp composed of finely ground ore and water, to which has been added (1) a small amount of certain oils, or (2) a small amount of certain acida or acid salts, or (3) a small amount of certain alkalis or alkaline salts, or (4) a small amount of a mixture of oil with acid or alkali, the sulphide particles in the ore are brought to the surface on the gas bubbles. These collect in a froth

Jan 1, 1917

By Paul D. Torrey

The water-flooding of oil sands has been widely practiced for many years in the Bradford and Allegany fields. Its effect upon the production of these fields has been almost phenomenal. In 1907 their estimated production was 3500 bbl. per day; in December, 1929, the combined production is estimated at 33,000 bbl. per day, an increase of almost 1000 per cent. in 22 years. This increase in production is directly attributable to the successful application of water-flooding, which has transformed the fields that were rapidly approaching abandonment into one of the most actively operated regions associated with the petroleum industry, and has made them important factors in the production of Pennsylvania Grade crude oil. The writer is indebted to many companies for information included in this paper. He is particularly grateful to the Sloan and Zook Co., the Petroleum Reclamation Co., George Bovaird, Jr., and the Associated Producers Co., of Bradford, Pa., who have generously made available much valuable data. Owing to the frequently competitive and confidential nature of property purchases, it has not always been possible to make specific reference to individual wells or properties; but wherever feasible, specific references have been made. Economic Factors The successful application of water-flooding for increasing the recovery of oil has been almost confined to the Bradford and Allegany fields. This has been due not only to legal restrictions in other fields and to very favorable sand conditions in the Bradford-Allegany region, but also to certain economic factors which are worthy of consideration. There has been some alarm regarding the effects of the rapidly increasing production upon the oil market but the writer is inclined to believe that future development can be made sufficiently flexible to meet the demand for this grade of oil. There has been a decided tendency toward consolidation of properties by mergers and purchases and, in addition, many of the individual producers are content to take advantage of floods advancing on their holdings from adjoining properties without developing their own on an intensive scale. Cooperative drilling along

Jan 1, 1930

By J. B. Austin, R. H. H. Pierce

IN developing a consistent picture of the thermal expansion of the commercial chromium steels, which cover a range of, carbon contents, it is desirable to know the expansion in the limiting case of the binary, carbon-free, iron-chromium alloys. We have, therefore, determined the thermal expansion of a series of five special alloys, ranging in chromium content from 3 to 10.5 per cent, with not more than 0.03 per cent carbon, over a temperature range extending beyond the transformation region; this low carbon content enables us to draw reasonably reliable conclusions as to the behavior of the carbon-free system. Moreover, the measurements serve to determine the beginning and the end of the alpha-gamma transformation; and they emphasize once more the fact that a transformation temperature determined by any method in which the specimen is .cooled at an appreciable rate is apt to be seriously in error, particularly if the metal contains a transformation-retarding element such as chromium or managanese. The lag, or undercooling, observed at the ?-a transformation is explained in terms of the influence of temperature on transformation velocity; the rather unusual shape of the ? loop is attributed to a change with temperature and with composition of the distribution of chromium between the alpha-iron and gamma-iron solid solutions. The exact composition of the alloys which were obtained through the courtesy of Dr. W. Rohn, of the Heraeus Vakuumschmelze A-G., is given in Table 1. Determinations of the linear thermal expansion and of transformation temperature were carried out in the vacuum dilatometer previously described,1 using a rate of heating and of cooling of 3.0° to 3.5° per minute unless otherwise stated. Magnetic susceptibility, which was measured in studying the rate of transformation, was determined with a magnetic balance, which also has. been described.2

Jan 1, 1935

By A. R. Jr. Amos

LOG washers have been used for many years in the washing of clay iron ores, phosphate rock and manganese ores, but not until the past 15 years have they been employed to any extent in the preparation of aggregate materials and fluxing stone. For a machine of such importance where tenacious clay or soft rock must be eliminated, there are few data generally available. The purpose of this paper is to set forth the results obtained from several operations, together with a few suggestions for planning a specific installation. Where the material to be washed out consists of loose surface soil, silt, or small amounts of quickly soluble clay, there is little competition with other forms of washers, because greater power and maintenance are required for the operation of log washers, but where the foreign matter is a stiff clay, such as occurs with high-calcium limestones and in marginal gravel deposits, the ability of other kinds of washers to eliminate com-pletely the hard clay balls is at least uncertain. Then the log washer comes into its own field, for with the breaking and churning action of the logs it will clean out the toughest clay. Even with material from the hydraulic dredge, if it contains tough clay, the log washer is desirable unless the gravel is subjected to a costly soaking and rehandling process. Recently there has been a considerable development in other types of machines to accomplish these results but it is not within the scope of this paper to make comparisons between competitive types, but to present the best obtainable data on log washers only. From the primitive design that gave it its name, a long log hewn from a tree, with paddles forged to shape from strap iron and attached by lag screws, the log washer has gradually been developed to the present all-steel type. As now manufactured, the log washer consists essentially of two built-up logs on which are mounted a series of paddles, carried by shafts fitted at the ends of the logs on bearings fastened outside the enclosing steel box, or trough, which is set at an angle of about 5° to 10° and into which the material is fed. Stuffing boxes at the places where the shafts pass through the box at the lower end are equipped with water-

Jan 1, 1936