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By J. S. Marsh

Joseph Priestley prepared oxygen on Aug. I, 1774, and noted with great surprise "that a candle burned in this air with a remarkable brilliant flame." On Aug. 2, 1774, some ironmaker possibly began to wonder if this substance could be used to increase his rate of production; at any rate, there is no disputing the fact that the notion of using oxygen for steelmaking in concentrations greater than that available in great abundance—as air—has been in existence for years. Action was delayed by the lack of enough oxygen at a cost within reach of the steelmaker. Within the last several years enough has been available to permit large-scale tests of its use for both combustion, with which this paper is concerned, and for decarburization. The literature is now enormous and easily available; it is sufficient here to cite three items of historic importance in that all are about 25 years old and in that all are remarkably consistent as far as they go, with what is known today.1,2,3 Significance of High-temperature Heat The principal function of the open-hearth furnace is to supply sufficient high-temperature heat to melt the charge and then to increase its temperature to a range suitable for tapping, ordinarily in the neighborhood of 2900°F. That heat is required to make steel is understood by everybody; however, there seems to be some confusion now and then about the significance of high-temperature heat. Transfer of energy—and heat is energy— is always from a point of higher potential to a point of lower potential and, other things being equal, the greater the potential difference, the greater is the rate of transfer of energy. In the open hearth the flame, of course, is the high-potential source. Perhaps the most satisfactory approach is through the notion of theoretical flame temperature, which is the ratio of heat input to the heat content of the combustion products,* the former is composed mainly of heat of combustion of the fuel plus sensible heat of the fuel plus sensible heat of the combustion air. Thus, flame temperature can be increased by increasing the value of the numerator, by decreasing the value of the denominator, or both. The first method is as old as the open-hearth process and, of course, makes use of preheated air; its possibilities have been by no means exhausted. The second method can be put into effect only by changing the composition of the combustion air, since the combustion of a given quantity of fuel produces a definite quantity of product, and since the denominator includes the non-reactive fraction of the air, principally nitrogen. In other words, the denominator consists of the volume of exit gas multiplied by its heat capacity and that volume consists of carbon dioxide and water vapor as reaction

Jan 1, 1949

By Norman Weiss

The need for more efficient utilization of labor in the metal-mining industry has been the subject of several recent editorials in the mining press, and one attractive possibility for such improvement lies in the designing of future milling plants particularly with economy of manpower in mind. We are accustomed to think of mill design as the selection and coordinated arrangement of process equipment, but if labor is to be efficiently utilized it must be given early consideration in planning the new mill. There are three good reasons for economizing in labor: (I) to reduce costs, not only in the form of wages but also in housing, hospital, welfare, and other obligations that a company accepts when a new man is added to the payroll; (2) to prepare for recurrent periods of manpower shortage, during which a well-designed plant can manage to get along with skeleton crews; (3) because a milling plant that must depend upon an inordinately large labor force for its operation and maintenance is certain to be inefficient in other respects, for many of the shortcomings in design that make necessary the excessive use of labor are generally not corrected merely by having too many men. A simple example of this is a poorly designed ore-feeding system : if this is inadequate to the extent that one man must be constantly unclogging feed chutes, it may help the situation to put two men or three at this task instead of one, but the feed rate will still be inconstant. First of the factors that affect labor saving is the location of the mill. This is often determined by transportation costs alone, and as a result the mill may be placed close to the mine regardless of the nature of the terrain. The designer must then adapt his layout to the conditions, favorable or not. This happens often at small properties, where capital investment may seem more important than operating expense. In most instances, however, a mill site carefully selected for the advantages it gives the designer in laying out the plant is the most economical in the long run, even if it involves a slight increase in cost of ore haulage. Given some freedom of choice, the design engineer may be able to find just the piece of ground that provides the proper gradient for the needs of the flowsheet, permits installation of essential yards and trackage, and perhaps supplies an excellent site for a tailing dam. Further justification for having placed the mill not too close to the mine sometimes emerges only years later as an opportunity to treat ores from other properties. When it is known from the beginning that the new mill will serve a number of scattered mines, a free choice of mill site is naturally stimulated. The most important single factor in limiting the labor requirements of a mill is its materials-handling system for bring-

Jan 1, 1947

By Norman Weiss

The need for more efficient utilization of labor in the metal-mining industry has been the subject of several recent editorials in the mining press, and one attractive possibility for such improvement lies in the designing of future milling plants particularly with economy of manpower in mind. We are accustomed to think of mill design as the selection and coordinated arrangement of process equipment, but if labor is to be efficiently utilized it must be given early consideration in planning the new mill. There are three good reasons for economizing in labor: (I) to reduce costs, not only in the form of wages but also in housing, hospital, welfare, and other obligations that a company accepts when a new man is added to the payroll; (2) to prepare for recurrent periods of manpower shortage, during which a well-designed plant can manage to get along with skeleton crews; (3) because a milling plant that must depend upon an inordinately large labor force for its operation and maintenance is certain to be inefficient in other respects, for many of the shortcomings in design that make necessary the excessive use of labor are generally not corrected merely by having too many men. A simple example of this is a poorly designed ore-feeding system : if this is inadequate to the extent that one man must be constantly unclogging feed chutes, it may help the situation to put two men or three at this task instead of one, but the feed rate will still be inconstant. First of the factors that affect labor saving is the location of the mill. This is often determined by transportation costs alone, and as a result the mill may be placed close to the mine regardless of the nature of the terrain. The designer must then adapt his layout to the conditions, favorable or not. This happens often at small properties, where capital investment may seem more important than operating expense. In most instances, however, a mill site carefully selected for the advantages it gives the designer in laying out the plant is the most economical in the long run, even if it involves a slight increase in cost of ore haulage. Given some freedom of choice, the design engineer may be able to find just the piece of ground that provides the proper gradient for the needs of the flowsheet, permits installation of essential yards and trackage, and perhaps supplies an excellent site for a tailing dam. Further justification for having placed the mill not too close to the mine sometimes emerges only years later as an opportunity to treat ores from other properties. When it is known from the beginning that the new mill will serve a number of scattered mines, a free choice of mill site is naturally stimulated. The most important single factor in limiting the labor requirements of a mill is its materials-handling system for bring-

Jan 1, 1947

INTRODUCTION The preceding chapters have brought us to a point in the mineral appraisal process where the composited sample values can now be used to estimate the grade and tonnage of the total mineral deposit. There are many techniques whereby drill hole composites and/or other sample data are used to assign grade and estimates to the surrounding rock. Matheron and his students have properly called such techniques extension functions. Before embarking upon a detailed discussion of extension functions, it is necessary that we take time to consider the concept of geostatistics as advocated by George Matheron who developed the "Theory of Regionalized Variables," which he published in 1962 (Matheron, 1971). The concept of regionalized variables has important application in the techniques of mineral appraisal. The position or location of a mineral sample within a deposit can be almost as important as its value. Geostatistics, when defined as "the application of the theory of regionalized variables* to the study of mineralized volumes of rock," takes into consideration the position as well as the magnitude of the value of the sample. The principles of geostatistics, as outlined by Matheron, represent a major step forward in the mineral evaluation process, because they provide a sound theoretical and practical basis for quantifying the geological concepts of (1) area of influence of a sample, (2) the continuity or lack of continuity of mineralization within the ore body, and (3) the lateral changes in mineralization according to the trend direction of an ore body and its orthogonal components; or in other words, a measure of the anisotropy of the deposit. Royle (1971) has defined the objects of geostatistic as being: "1. To estimate the most likely value of blocks of ore, or the values of the whole deposit; and 2. to estimate the errors of such estimates. This latter is important as, in addition to providing a check on unwarranted optimism, it shows where more valuation work may be needed." Because of the great importance of these concepts in mineral evaluation, an introduction into the theory of regionalized variables, and the study of a practical approach to its application is outlined here. REGIONALIZED VARIABLES VS. RANDOM VARIABLES Classical statistics, as discussed in earlier chapters, grew out of the study and application of probability theory. Probability is concerned with the outcome of random events and therefore classical statistics is built upon the theory of random variables, i.e., the probability of independent events. The validity of most statistical inferences depends upon sample randomness being assured for unbiased results. Where independent events cannot be assumed the results of statistical inference becomes suspect. On the other hand, geostatistics is concerned with variables that have position in space as well as magnitude, hence the term regionalized variables. Mineral deposits are not the only field to which the theory of regionalized variables is applicable. Many natural phenomena that demonstrate a relationship between change in magnitude and position in space are amenable to application of geostatistical techniques. Mineral deposits vary greatly in their geosta-

Jan 1, 1980

By Howard R. Keil

PRIOR to World War II, approximately 500 tons per day, or one-third of the ore being shipped to the Golden Cycle Mill at Colorado Springs, Colo., from the Cripple Creek district, was being treated in the flotation plant. The remaining 1000 tons, along with the flotation concentrates, received the usual roasting and cyanide treatment. Since it was not possible to make a disposable tailing on the general run of Cripple Creek ores by flotation alone, it was necessary to treat the flotation tailings by cyanidation, along with the roasted ore. By this treatment, an overall economical tailing could be made. The gold ores from the Cripple Creek district are the highly siliceous sulphotellurides with approximately 3 pct total sulphides. In the lower grade ores most of the values are found in very finely disseminated pyrite. In some of the higher grade ores the tellurides, calaverite and sylvanite, can be recognized. After several years of floating Cripple Creek gold ores, having a very low mineral content, it was concluded that this type of ore required a Type of flotation machine that would give a rather violent aeration and agitation. This action produced a fairly deep froth column which contained not only the free mineral, principally pyrite, but also most of the middling product; this was most essential in producing a low grade tailing by flotation alone that could be discarded to waste. After investigating most of the current types of flotation machines, it was decided to convert to the Fagergren type. During World War II, the flotation plant was modified to handle lead and zinc ores. The treatment of these ores was carried on until April 1946. At this time the flotation plant was again reconverted to handle the Cripple Creek ores. SELECTING ORES FOR FLOTATION During the period of reconversion a considerable amount of experimental work was carried on in the laboratory to determine if a disposable tailing could be made by flotation alone, on certain selected ores from the Cripple Creek district. It was found that most of the dump ores and a few of the low grade mine ores could be treated by this method with very satisfactory results. After the preliminary test work in the laboratory, it was decided to carry on further work on a plant-size scale to see if similar results could be obtained. On April 15, 1946, a part of the plant was put into operation as a pilot plant. The various ores that had been found suitable for treatment by this method in the laboratory, were run through the pilot plant at the rate of 200 tons per day for a period of several months. Results were so encouraging that it was decided to put the plant in full-scale operation. Since that time plant capacity has been increased from 500 to 1000 tons per day. This has been done not by the installation of more machinery but by (I) crush-

Jan 1, 1947

By K. M. Fagin, D. W. Carter

Six new oil fields were discovered in the East and East Central Texas district during 1942. The Coke and Quitman fields, in Wood County, at this time appear to be the two most important oil discoveries for the year. The. four other oil fields discovered were Concord, in Anderson County; Kildare, in Cass County; Weiland (ClubLake), in Hunt County; and Larissa, in Cherokee County. The Rodessa lime in the Chapel Hill field, Smith County, provided the only new oil zone in older fields. The Hawkins field, Wood County, was the most active in drilling operations, 125 new wells being completed during the year. The Chapel Hill field tied the Coke field for second place with 30 completions each. The third most active field was Kildare, with 10 completions. Like the other oil-producing districts of the country, wartime restrictions reduced the number of oil and gas-well completions to 265 in 1942, compared with 964 completions in 1941. This represents a drop of 72 per cent and only a little more than one half enough to replace the 437 producing wells abandoned in the district during the year. Tn addition, the number of producing wells temporarily shut down nearly tripled, far two principal reasons: (I) the rule of the Petroleum Administration for War preventing operators from equipping more than, one well on each 10 surface acres with pumping or artificial-lift equipment, and (2) the Railroad Commission's issuance of various orders permitting the transfer of allowable for wells having high water-oil ratios and high gas-oil ratios to other wells capable of producing the same with less waste of reservoir energy. No changes were made in prices of crude oil in the district during 1942. Production and Probation The district produced 158,928,281 bbl. of oil and distillate during 1942, compared with 163,566,695 bbl. during 1941, which represents a decrease of 3 per cent. The East Texas field produced 120,680,595 bbl. of oil, compared with 130,377,793 during 1941; a reduction of 9,697,198 bbl., or 7.4 per cent. The production of this field represents 75.9 per cent of the district total, compared with the 79.7 per cent that it furnished in 1941. The district had an estimated basic daily oil allowable of 623,242 bbl. on Dec. 31, 1942. Approximately 31.8 per cent of the production in Texas during 1942 was supplied by this district, compared with 33 per cent during 1941- Changes in the annual production of newer and flush fields in this district are attributable either to a difference in the number of wells producing during the year or to changes in basic allowable and number of shutdown days due to shifting market dconditions brought on by the war. All regularly prorated fields in the district were shut down 123 days. Major exceptions were the East Texas field, closed128 days; Hawkiis, shut down 106 days; and Cayuga, Sulphur Bluff, Talco, and Rodessa, which

Jan 1, 1943

By D. W. Carter, K. M. Fagin

Six new oil fields were discovered in the East and East Central Texas district during 1942. The Coke and Quitman fields, in Wood County, at this time appear to be the two most important oil discoveries for the year. The. four other oil fields discovered were Concord, in Anderson County; Kildare, in Cass County; Weiland (ClubLake), in Hunt County; and Larissa, in Cherokee County. The Rodessa lime in the Chapel Hill field, Smith County, provided the only new oil zone in older fields. The Hawkins field, Wood County, was the most active in drilling operations, 125 new wells being completed during the year. The Chapel Hill field tied the Coke field for second place with 30 completions each. The third most active field was Kildare, with 10 completions. Like the other oil-producing districts of the country, wartime restrictions reduced the number of oil and gas-well completions to 265 in 1942, compared with 964 completions in 1941. This represents a drop of 72 per cent and only a little more than one half enough to replace the 437 producing wells abandoned in the district during the year. Tn addition, the number of producing wells temporarily shut down nearly tripled, far two principal reasons: (I) the rule of the Petroleum Administration for War preventing operators from equipping more than, one well on each 10 surface acres with pumping or artificial-lift equipment, and (2) the Railroad Commission's issuance of various orders permitting the transfer of allowable for wells having high water-oil ratios and high gas-oil ratios to other wells capable of producing the same with less waste of reservoir energy. No changes were made in prices of crude oil in the district during 1942. Production and Probation The district produced 158,928,281 bbl. of oil and distillate during 1942, compared with 163,566,695 bbl. during 1941, which represents a decrease of 3 per cent. The East Texas field produced 120,680,595 bbl. of oil, compared with 130,377,793 during 1941; a reduction of 9,697,198 bbl., or 7.4 per cent. The production of this field represents 75.9 per cent of the district total, compared with the 79.7 per cent that it furnished in 1941. The district had an estimated basic daily oil allowable of 623,242 bbl. on Dec. 31, 1942. Approximately 31.8 per cent of the production in Texas during 1942 was supplied by this district, compared with 33 per cent during 1941- Changes in the annual production of newer and flush fields in this district are attributable either to a difference in the number of wells producing during the year or to changes in basic allowable and number of shutdown days due to shifting market dconditions brought on by the war. All regularly prorated fields in the district were shut down 123 days. Major exceptions were the East Texas field, closed128 days; Hawkiis, shut down 106 days; and Cayuga, Sulphur Bluff, Talco, and Rodessa, which

Jan 1, 1943

By B. M. Larsen

IN endeavoring to put the art of the steelmaker on a more scientific basis, as a means of securing closer control of the product, we must be severely critical of the basis of any theory we use. In particular, we must be careful to distinguish between factors that are primary and those of only secondary importance. The concentration relations that determine the slag-metal equilibria, which are usually more or less closely attained, are of course of primary significance, but a clear picture of the whole process requires that the actual rates of the several reactions be taken properly into account. At the high temperature of the steelmaking furnace, all reactions might be thought to be very rapid, but some of them in fact are not; the essential causes of this condition are important to a proper understanding of the process. This paper aims to present, and to justify, the viewpoint that the most significant reaction is the oxidation of carbon in the metal, the progress of which determines the oxygen pressure levels in slag and metal and produces stirring effects, all of which influence the course of the process as a whole. REACTION RATES AT STEELMAKING TEMPERATURES General experience in reaction rates makes it almost certain that at steelmaking temperatures equilibrium is attained practically instantaneously when the reactants are well distributed in a single liquid phase -that is, in the so-called homogeneous reactions. The actual slowness of some of the reactions in the open-hearth furnace must therefore be attributed to a relatively slow rate of diffusion within the slag or metal phase, which limits the rate at which the reactants can meet each other in the liquid steel or at its surface. That the reactions can be made to go with great rapidity, by proper mixing and stirring of the reacting phases, is indicated by the following illustrations: I. In the Bessemer process there is intimate contact between air and the whole mass of metal, and the reactions are complete in a few minutes. 2. Perrin1 has demonstrated that by pouring liquid steel into slag contained in a deep ladle, and thereby producing almost a slag-metal emulsion, the phosphorus or oxygen content of the steel is adjusted immediately. 3. Barret, Holbrook and Woods observed a quite rapid rate of desulphurization when powdered calcium carbide was stirred vigorously into liquid iron. 4. When a spoonful of liquid steel is poured into a mold containing aluminum wire, the formation and precipitation of alumina occurs in the fraction of a second required to freeze the surface layer of the tiny ingot. The first three examples all show that any means of increasing the effective surface between slag and metal and promoting intimate mixture of the reacting phases, thereby obviating the limitation imposed by diffusion, will enhance the speed of the steelmaking process.

Jan 1, 1941

By J. H. Frye, J. W. Caum

ONE of the most important methods of increasing the hardness of metals is alloying. In spite of the widespread use of alloys, the fundamental mechanism of alloy hardening is little understood. This is true even of the simplest form of alloy, the primary substitutional solid solution in which solute atoms substitute for solvent atoms at random in the crystal lattice of the latter. A fundamental understanding of the mechanism of solid-solution hardening would be important, both because of the widespread use of alloys of this type and because of the light that might be thrown on the mechanism of hardening in more complicated alloys. The present investigation covers the hardness of primary substitutional solid solutions of zinc, gallium,, germanium; and arsenic in copper. All of these are B subgroup elements from the third period of the periodic table. Cu, Zn, Ga, Ge, and As are in groups I, II, III, IV, and V, respectively and lie just to the right of the transition elements. Because of their cost, it is unlikely that Ga-Cu and Ge-Cu solutions will ever be of commercial importance, but the intent of this study has been to discover some of the fundamentals of solid-solution hardening and it has been demonstrated that such a study is far more likely to be fruitful if alloys are made up on the basis of position of the constituent elements in the periodic table than if commercially important alloys are used. Many investigations have. been made of the hardness of substitutional solid solutions, but lack of attention to purity of the metals, infrequent grain-size control, and the use of varying testing techniques have virtually invalidated any comparisons. The purpose of most investigations has been to solve immediate problems and not to solve the primary problem: Why do solid solutions usually have a greater hardness than pure metals? PREVIOUS WORK Theories have been advanced to account for the hardness of solid solutions,, but relatively little experimental work has been done. Perhaps the first experimental work of merit was that of Norbury1 on copper alloys. He showed that for several alloys there was a correspondence between the hardness of one atomic per cent solutions and atomic volume of the solutions. More recently Brick, Martin, and Angier2 have investigated the effect of various solute elements on the hardness of copper. They concluded that the hardening effect of these solutes depended "primarily on the difference in atomic volume of solute and solvent or, relatedly, upon the parameter, change of the solvent or the extent of solid solubility." They also observed the effect of these elements on hardness and texture developed by rolling and by annealing of rolled material. Austin3 examined the hardness and response to heat-treatment of various iron solid solutions. Frye and Hume-Rothery4 measured the hardness of a number of silver solid solutions containing approximately

Jan 1, 1943

By A. W. Bitner, A. W. Asman

An analysis is made of three different types of section production units that represent the manner in which most of the nation's bituminous coal is produced. The general delays and production characteristics of these sections are presented along with a method for evaluating section performance based on actual and theoretical production characteristics. THE forerunner of the modern mechanical loading machine first entered the mines in 1890—a Stanley header with a conveyor. Since then progress has been substantial, both in the design and application of mechanized production units. Mechanization is almost a necessity for survival in the economy of today. In this paper an analysis is made of three types of sections, and a method for evaluating section performance based on present production characteristics and theoretical characteristics is presented. In mechanical loading mining sections the loading machine is the unit directly responsible for production. If the face preparation units provide a plentiful supply of properly prepared coal and the transportation system is coordinated and adequate, the loader will be idle a minimum of time. If either of the above do not perform adequately or other delays occur, the effect on production will be reflected in the performance of the loading machine. Therefore, attention is focused on the loading machine and factors that affect the overall performance of the production unit. Three complete mechanized production units are presented for analysis: A track section, a trackless section using battery-powered shuttle cars, and a trackless section using cable-reel shuttle cars. These particular sections were chosen for the following reasons: 1—The daily tonnage and mining conditions are approximately the same. 2— Production in each is 10 to 20 pct above the daily average. 3—The production characteristics and delays are average and typical. 4—They represent the manner in which the most of the nation's bituminous coal is produced. A. W. ASMAN, and A. W. BITNER, Members AIME, are Chief, and Research Assistant, respectively, Div. of Mining, The Pennsylvania State College, State College, Pa. Discussion on this paper, TP 3140F, may be sent to AIME by Oct. 31, 1951. Manuscript, Feb. 22, 1951. St. Louis Meeting, February 1951. Section A Fig. 1 is a layout for the track mining section showing the development to date, the projected plan and the cuts loaded on the shift studied. The seam mined averages 96 in. in thickness with a fireclay bottom and a roof of 10 in. of drawslate topped by sandstone. The mineability is considered good, and roof support is not a difficult problem. Two locomotives are used in the section to minimize the losses occurred in trip changing. The places are driven 20 ft wide, and the crosscuts are angled to permit fast tramming of the equipment. Table I lists the equipment and labor that make up the section. ANALYSIS Production Characteristics: The average loading rate for eight loading machines studied of this type is 1.81 tons per min. This one at 2.78 is considerably above average.

Jan 1, 1952

By J. S. McNeil, J. U. Messenger

In the drilling of oil wells the control and prevention of lost circulation of the drilling- fluid is a oroblem which is frequently encountered; in many cases existing materials and methods for alleviating this condition have not been adequate. For severe cases of lost circulation in which the simpler methods, such as application of various bridging materials to the mud system, have proven unsatisfactory. a new material and method for applying to the loss zones have been developed which appear to he superior to existing techniques in many respects. The material, called a clay cement, is capable of being handled as a drilling fluid after initial mixing of the solitl ingredients with water and may be pumped down the drill pipe and squeezed into loss zones. After a short period, the material develops a very high gel strength which seals off the zone against further losses of the drilling fluid. In field tests, the process has been demonstrated to be a very effective method for combatting lost circulation. INTRODUCTION Methods of treating lost circulation in rotary-drilled wells by the addition of special materials to drilling fluids have long been in the process of development and are continuing to improve.' However, the annual drilling costs which can be traced directly to lost circulation difficulties still run into the millions of dollars. The loss of mud materials into highly permeable zones may range up to $50,000 per well in some areas. In addition to mud costs, excessive requirements of casing, cement; rig time, and the attendant blowout hazards further emphasize the importance of the need for improved methods of combatting lost circulation. The shortcomings of presently-used materials and methods have led to the development of a new lost returns material in the form of a time-setting clay cement. In field tests this material has proven very successful in plugging off loss zones. which other more conventional materials had failed to do. REVIEW OF PRESENT CORRECTIVE MEASURES The proper control of such operating factors as pump pressure, clearance between pipe and hole, and speed of running pipe in a holez is of primary importance in preventing and minimizing lost circulation problems. These factors, however, concern matters of drilling technique and do not directly involve lost circulation materials. Aside from setting casing past loss zones, three principal methods are generally employed for the purpose of avoiding or combatting lost circulation: (1) adjustment in properties (principally density) of the drilling fluid, (2) addition of fibrous, flaky, granular or other types of bridging materials to the mud system, and (3) the application of cements to the loss zones. The latter method is usually employed only after the first two have proven unsuccessful. In Table I are listed some advantages and disadvantages of the common corrective measures. Frequently, a combination of bridging material and cementing material is used." This combination is based on the premise that a bridge will

Jan 1, 1952

By R. G. Ward, John Henderson. R. G. Hudson, G. Derge

Densities of melts of the iron oxide-silica system in contact with solid iron have been measured by the maximum hubble pressure method in the composition range O to 37 wt pct SiOz and the temperature range 1255 to 1410C. The constitution of the melts is discussed and it is postulated that the structure changes from a dislribution of iron ions in an oxygen ion network at pure "FeO" to a distribution. of iron ions in a network of silicate tetrahedra at the orthosilicate composition. JOHN HENDERSON, Junior Member AIME, was formerly with the Metals Research Loborotory, Carnegie Institute of Technology, Pittsburgh, Pa., on leave from Broken Hill Proprietary Co., Ltd., Research Division, Shortland, Australia. R. G. HUDSON, formerly with Metals Research Laboratory, is now with the John Jay Hopkins Loborotory for Pure and Applied Science, General Atomic Division, General Dynamics Corp., LaJolla, Calif. R. G. WARD, was formerly with the Department of Metal lurgical Engineering, Carnegie lnstitute of Technology, while on leave from the Department of Metallurgy, University of Sheffield, England. G. DERGE, Member AIME, is Jones and Laughlin Professor of Metallurgical Engineering, Carnegie lnstitute of Technology. Manuscript submitted January 19, 1961. ISD The system iron oxide-silica is an important one metallurgically because it forms the basis of several complex slag systems in use for industrial smelting and refining processes. In recent years considerable work has been done on liquids of this system but there are still many points of difference among workers using different experimental techniques and theoretical approaches. Phase equilibria/"3 activity,4-6 electrical conductivity,' current efficiency,' transference number,8 viscosity,9 surface tension,'' and density" measurements have all contributed to an understanding of the problem. Measurement of density is one procedure which is directly indicative of liquid structure since any deviation from ideality must be a result of structural interactions. Liquids of the iron oxide-silica system are of special interest because this is one of the few metal oxide-silica systems on which measurements can be carried out conveniently over the entire composition range from pure oxide to silica saturation. This includes the range of high basicity which has received relatively little attention in other systems. Although one investigation of density in this system has previously been undertaken," the results seem of sufficient importance to warrant the independent redeter-mination reported here.

Jan 1, 1962

W. D. BRENNAN,* Cheyenne, Wyo. (written discussion?).-My experience has been that, where possible, it is preferable for each foreman to employ his own men, rather than to have them handled through an employment bureau. The fact that each foreman comes into direct contact with the man before he is put to work gives him an opportunity to choose, at certain times, the kind and class of men that he wishes. Where possible, after a man is employed he is sent to a central office where a complete history of each individual is kept on a card. If a man has previously been in the employ of the Company, his history can be obtained from this card, and if for any reason he is not wanted he can be refused work at the time he reports to, the central office. In connection with Workman's Compensation costs, we in Wyoming feel that although the rates of compensation paid may in some cases be rather low our law works satisfactorily. As the State and the number of employees are small, compensation cases are handled through Judges of the various District Courts. In the State Treasurer's Department, a few clerks were added to look after the handling and issuing of warrants and compiling of statistics. Most of the large employers have an arrangement by which a joint claim and assent, specifying the amount of compensation due, is made tip by the employer and signed by the workman. This is forwarded, to the Judges so that personal investigation of individual cases is not necessary. In this manner, compensation is promptly received and' overhead expenses of operation of the law is kept at the minimum. The law requires each employer to pay into the State Treasury, for the benefit of the industrial fund, a sum equal to 1.5 per cent. of the money earned by each employee, engaged during each calendar month of such employment. Each employer contributes monthly, unless the sum heretofore contributed, after deducting all payments made on account of injuries to his employees, shall equal a full 1.5 per cent. of his annual pay roll, computed by multiplying his current monthly pay roll by twelve, and shall likewise be not less than ($5000). It has been found during the years that this law has been in effect, that a number of the larger employers have been exempt from payment for from five to eight months per year, so that in some cases, even in coal nines, industrial insurance has cost less than 0.75 per cent.

Jan 3, 1919

By Howard R. Keil

Prior to World War 11, approximately 500 tons per day, or one-third of the ore being shipped to the Golden Cycle Mill at Colorado Springs, Colo., from the Cripple Creek district, was being treated in the flotation plant. The remaining 1000 tons, along with the flotation concentrates, received the usual roasting and cyanide treatment. Since it was not possible to make a disposable tailing on the general run of Cripple Creek ores by flotation alone, it was necessary to treat the flotation tailings by cyanidation, along with the roasted ore. By this treatment, an overall economical tailing could be made. The gold ores from the cripple creek district are the highly siliceous sulphotel-lurides with approximately 3 pet total sulphides. In the lower grade ores most of the values are found in very finely disseminated pyrite. In some of the higher grade ores the tellurides, calaverite and sylvanite, can be recognized. After several years of floating cripple Creek gold ores, having a very low mineral content, it was concluded that this type of ore required a type of flotation machine that would give a rather violent aeration and agitation. This action produced a fairly deep froth column which contained not only the free mineral, principally pyrite, but also most of the middling product; this was most essential in producing a low grade tailing by flotation alone that could be discarded to waste. After investigating most of the current types of flotation machines, it was decided to convert to the Fagergren type. During World War 11, the flotation plant was modified to handle lead and zinc ores. The treatment of these ores was carried on until April 1946. At this time the flotation plant was again reconverted to handle the Cripple Creek ores. Selecting Ores for Flotation During the period of reconversion a considerable amount of experimental work was carried on in the laboratory to determine if a disposable tailing could be made by flotation alone, on certain selected Ores from the Cripple Creek district. It was found that most of the dump Ores and a few of the low grade mine ores could be treated by this method with very satisfactory results. After the preliminary test work in the laboratory, it was decided to carry on further work On a plant-size scale to see if similar results could be obtained. On April 15, 1946, a part of the plant was put into operation as a pilot plant. The various ores that had been found suitable for treatment by this method in the laboratory, were run through the pilot plant at the rate of 200 tons per day for a period of several months. Results were so encouraging that it was decided to put the plant in full-scale operation. Since that time plant capacity has been the from 500 to 1000 tons per day. This has been done not by the installation of more machinery but by (I) crush-

Jan 1, 1949

By John W. Vanderwilt

The unpredictable behavior of ground movement and subsidence has complicated the problems that attend the extraction of large quantities of ore. Special studies, particularly relating to coal mining, have yielded such a voluminous literature and so many involved controversial theories that a partial review would be difficult. Limited space makes any kind of a review impractical. The features to be considered cover only a relatively small part of the broad problems of ground movement and subsidence, but it is believed that this small part is critical. The practical aspects are important, since they bear directly on safety of mine workings, on recovery of ore and on dilution of ore in block caving and related systems for extracting large quantities of rock. The ground movement to be described occurs outside the vertical boundaries of a caved block in the area that is commonly referred to as being in the "zone of draw." "Draw" is a term that originated in the subsidence problems related to coal mining, and it is defined by a line drawn from the margin of the area caved underground to the most distant fracture at surface on the same side of the caved area as shown in Fig. I.' A line thus drawn is called the cave line, and its angle with respect to the horizontal is the cave angle or angle of draw. It is understood that the line is taken normal to the limit of mining, and in a vertical plane. The prevailing theories as to draw and angle of draw assume that appreciable movement occurred along the cave line, which has been described as a fracture resulting from the shearing action brought about by the weight of the overlying load. Fig. 3 shows diagrammatically the mechanics of ground movement adjacent to an area of subsidence according to the prevailing theory of draw (A, from Royce2) and, for comparison, ground movement observed in the Climax mine (B). The text in Peele's Handbook2 referring to Fig. 2 does not state the meaning of the "original position of top of workable ore" in the rectangular space above "ore in place," and the arrows are not explained. However, this presentation is most concerned with the zones outside the rectangle. According to the prevailing theory, as shown at the extreme left under A, Fig. 2, the vertical tension cracks at surface change at a shallow depth to shear fractures forming the cave line, and it is assumed that appreciable movement takes place along the cave line toward and into the subsiding caved block. The mechanics of ground movement observed in the Climax mine, as shown under B, Fig. 2, does not accord with the prevailing theory, particularly as regards the cave angle and draw. The vertical tension cracks seen at surface die out at depths of 150 to 225 ft. and shear fractures do not develop. Movement is confined at surface to a mantle of rock 50 to roo ft.

Jan 1, 1949

By J. R. Thoenen, M. C. Malamphy, G. K. Dale

The beginning of the war and the events leading up to it precipitated a near crisis in the aluminum industry. Demands for the metal reached proportions far beyond the prewar production capacities and, in addition, the submarine menace seriously curtailed the importation of bauxite from South America, hitherto a chief source of high-grade ore. The situation required an intensive search for domestic ore to augment the reserves and in October 1941 Congress directed the Department of the Interior to investigate the extent, mode of occurrence, and quality of bauxite in the United States. In December of that year the Bureau of Mines and the Geological Survey began the search for bauxite in Arkansas, where more than go per cent of the domestic ore had been produced and where the greatest amount of bauxite was known to occur. The program involves the geophysical and geological investigation of the Arkansas bauxite region and the core drilling of areas considered favorable for the occurrence of bauxite deposits. Cores taken from the bauxite-kaolin zone are sampled and analyzed in the Bureau of Mines laboratory in Little Rock. The information from each of the deposits discovered is then assembled, the bauxite is graded with respect to its possible utility, tonnage estimates are made, and the whole is presented in the form of a war minerals report. Thirty-eight new bauxite deposits had been discovered and investigated at the end of the calendar year 1944, and the presence of several others had been indicated by the drilling. More than 5000 holes had been drilled throughout the bauxite region, and more than 60,000 chemical analyses had been made of samples taken from the bauxite-kaolin zone. A study of the chemical analyses led to certain general conclusions not only with regard to the chemical composition of Arkansas bauxite, but also with regard to its component minerals. Charts and diagrams based on these conclusions have been developed for practical use by the Bureau of Mines: (I) to serve as a check against laboratory analyses, (2) to present tonnage estimates of ore bodies based on mineral composition, (3) to illustrate the relationship of tonnages of bauxite to the alumina, silica, and iron content, and (4) to serve as a control for mining operations by providing a means for quick estimates of the value of the ore from a partial analysis of its chemical constituents. The use of charts and diagrams similar to those discussed in this paper-- is not new. The use of the trilinear diagram for studying the ultimate analyses of coals as of proposed by Ralston in Bureau of Mines Technical Paper 93 (1915) showed that the various ranks of coal fell in different areas on the diagram and that volatile matter, calorific value and other properties could also be plotted by the use of contours. A considerable subsequent literature, largely on classification of coals, has accurnulated since then, showing the utility

Jan 1, 1948

By J. R. Thoenen, M. C. Malamphy, G. K. Dale

The beginning of the war and the events leading up to it precipitated a near crisis in the aluminum industry. Demands for the metal reached proportions far beyond the prewar production capacities and, in addition, the submarine menace seriously curtailed the importation of bauxite from South America, hitherto a chief source of high-grade ore. The situation required an intensive search for domestic ore to augment the reserves and in October 1941 Congress directed the Department of the Interior to investigate the extent, mode of occurrence, and quality of bauxite in the United States. In December of that year the Bureau of Mines and the Geological Survey began the search for bauxite in Arkansas, where more than go per cent of the domestic ore had been produced and where the greatest amount of bauxite was known to occur. The program involves the geophysical and geological investigation of the Arkansas bauxite region and the core drilling of areas considered favorable for the occurrence of bauxite deposits. Cores taken from the bauxite-kaolin zone are sampled and analyzed in the Bureau of Mines laboratory in Little Rock. The information from each of the deposits discovered is then assembled, the bauxite is graded with respect to its possible utility, tonnage estimates are made, and the whole is presented in the form of a war minerals report. Thirty-eight new bauxite deposits had been discovered and investigated at the end of the calendar year 1944, and the presence of several others had been indicated by the drilling. More than 5000 holes had been drilled throughout the bauxite region, and more than 60,000 chemical analyses had been made of samples taken from the bauxite-kaolin zone. A study of the chemical analyses led to certain general conclusions not only with regard to the chemical composition of Arkansas bauxite, but also with regard to its component minerals. Charts and diagrams based on these conclusions have been developed for practical use by the Bureau of Mines: (I) to serve as a check against laboratory analyses, (2) to present tonnage estimates of ore bodies based on mineral composition, (3) to illustrate the relationship of tonnages of bauxite to the alumina, silica, and iron content, and (4) to serve as a control for mining operations by providing a means for quick estimates of the value of the ore from a partial analysis of its chemical constituents. The use of charts and diagrams similar to those discussed in this paper-- is not new. The use of the trilinear diagram for studying the ultimate analyses of coals as of proposed by Ralston in Bureau of Mines Technical Paper 93 (1915) showed that the various ranks of coal fell in different areas on the diagram and that volatile matter, calorific value and other properties could also be plotted by the use of contours. A considerable subsequent literature, largely on classification of coals, has accurnulated since then, showing the utility

Jan 1, 1948

By J. L. Bray

ACCELERATED programs, as discussed in this paper, refer to the year-around operation of a college or university with three sixteen-week or four twelve-week terms per year, with pauses between sufficient only to allow the administrative group to perform their functions. In most engineering schools, under such conditions, the conventional four-year course can be condensed to two years and eight months. These accelerated programs of study, which now exist in most of our technical institutions, were forced upon us under the influence of the outburst of wartime patriotism, perhaps one might go so far as to call it hysteria. Many of us felt and hoped that these programs were temporary expedients, but the cold hard threat of permanency now rears its head; consequently we should examine the merits and shortcomings of the new order, and evaluate its effect on our educational system, since it may persist in some form in the postwar years, because of the changing political and financial situation. Many engineering students are being educated in state supported institutions

Jan 1, 1944

By Walter S. Lutz, J. T. Griffith

The rainfall during the last six months of 1942 in Scranton and vicinity was 24.06 in.—only 4.35 in more than the average for this district in any equivalent period—yet that rain forced The Hudson Coal Co. to handle 38.8 tons of water for every ton of coal mined. It filled to overflowing, or to a higher level, 14 flooded mine areas holding, in total volume, 8.3 billion gallons of water in storage; brought about a pumpage of 11.4 billion gallons in the months of December 1942 and January, February and March 1943 Half of the total energy generated or purchased (44,322,980 kw-hr.) was required to keep the mines sufficiently free of water to permit the mining of coal during a period of much needed output. Fig. I shows the extent to which this flooding of exhausted and idle properties has proceeded, and is known to be proceeding further, at the upper end of the Northern field. This rainfall (24.06 in.) means 80,559,444 tons of water on approximately 46.2 sq. miles of area tributary to the pumping plants. During the high rainfall period, 72,687,661 tons went underground, being pumped at the stations in this territory. This means an inflow of 88per cent, a runoff of 12 per cent compared with 64 per cent during normal conditions in a normal region. During this period no floods, either surface or underground, had to be dealt with, although the streams and rivers were high on several occasions. In general, the rainfall for the first three months of 1943 can be described as heavy but not abnormal.9 These figures not only indicate the large volumes of water to be handled but, by their very size, they also emphasize that the mine-water problem is not to be conquered, at least from an economical standpoint, by merely buying and installing more and more pumps. Into the solving of this water problem must go much planning, adhering to the principle of keeping the highest percentage of water at the highest possible level for the longest period of time; the storage of huge volumes in sumps capable of being reduced after the flood inflow and at rates less than the inflow; plans for prevention of surface inflow; provision of the minimum of pumping capacity arranged to as nearly 100 per cent pumping load factor as is possible; intercompany joint pumping plants; the conducting of water from one plant to another and from one property to another over distances measured in miles; priorities in power to the threatening situations; and. balance of the necessities and dangers existent in one colliery over another, day by day, when quantities of water are running high. Despite these astronomical figures of water volumes, their disposal to the surface is accomplished reasonably cheaply because, although the annual cost of $575,020 is a large sum, the cost per ton is about 0.1168 cents. Credit for this goes

Jan 1, 1947

By J. T. Griffith, Walter S. Lutz

The rainfall during the last six months of 1942 in Scranton and vicinity was 24.06 in.—only 4.35 in more than the average for this district in any equivalent period—yet that rain forced The Hudson Coal Co. to handle 38.8 tons of water for every ton of coal mined. It filled to overflowing, or to a higher level, 14 flooded mine areas holding, in total volume, 8.3 billion gallons of water in storage; brought about a pumpage of 11.4 billion gallons in the months of December 1942 and January, February and March 1943 Half of the total energy generated or purchased (44,322,980 kw-hr.) was required to keep the mines sufficiently free of water to permit the mining of coal during a period of much needed output. Fig. I shows the extent to which this flooding of exhausted and idle properties has proceeded, and is known to be proceeding further, at the upper end of the Northern field. This rainfall (24.06 in.) means 80,559,444 tons of water on approximately 46.2 sq. miles of area tributary to the pumping plants. During the high rainfall period, 72,687,661 tons went underground, being pumped at the stations in this territory. This means an inflow of 88per cent, a runoff of 12 per cent compared with 64 per cent during normal conditions in a normal region. During this period no floods, either surface or underground, had to be dealt with, although the streams and rivers were high on several occasions. In general, the rainfall for the first three months of 1943 can be described as heavy but not abnormal.9 These figures not only indicate the large volumes of water to be handled but, by their very size, they also emphasize that the mine-water problem is not to be conquered, at least from an economical standpoint, by merely buying and installing more and more pumps. Into the solving of this water problem must go much planning, adhering to the principle of keeping the highest percentage of water at the highest possible level for the longest period of time; the storage of huge volumes in sumps capable of being reduced after the flood inflow and at rates less than the inflow; plans for prevention of surface inflow; provision of the minimum of pumping capacity arranged to as nearly 100 per cent pumping load factor as is possible; intercompany joint pumping plants; the conducting of water from one plant to another and from one property to another over distances measured in miles; priorities in power to the threatening situations; and. balance of the necessities and dangers existent in one colliery over another, day by day, when quantities of water are running high. Despite these astronomical figures of water volumes, their disposal to the surface is accomplished reasonably cheaply because, although the annual cost of $575,020 is a large sum, the cost per ton is about 0.1168 cents. Credit for this goes

Jan 1, 1947