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By C. G. Dunn

With respect to theories of recrystalliza-tion in metals plastically deformed. it has been said that the present status of this subject is far from satisfactory.1 It may also be said that before any mechanism of recrystallization for metals and alloys can be set forth in a satisfactory manner, there must be made available considerable data on orientation changes that occur during the deformation and recrystallization processes. Although extensive data have been published on recrystallization in single crystals and in poly-crystalline specimens, more results of a type that can be classified according to simple orientation changes would be desirable in this complex field. It might even be said that before classifications are made according to types of orientation changes, it may be possible to classify a considerable amount of data into certain kinds of orientation states if groups of common or nearly common orientation occur. Methods for computing the probability of occurrence for various types of groups have been published2 and it has been pointed out in particular that it should be possible to analyze orientation data for high-order twin relationships between old and new grains even when agreement is not at all exact. In this connection, work on recrystallization in silicon ferrite reported in a paper concerned with complex groups of annealing twins3 indicated that some data were consistent with primary nucleation OCcurring according to a second-order or a third-order twin transformation. However, further work in this latter direction was definitely needed. It is, therefore, the purpose of the present paper to report data and analyses for primary nucleation in silicon ferrite following small deformations that have been carried Out at the Pittsfield Works' Laboratory of the General Electric Co. Analyses have been made with the aid of standard groups of twins that are reported elsewhere.4 PReparation oF Specimens and Experimental Procedure The material used in the present investigation was taken from the same heat of steel as that .used in a prior report.3 The finished strip in both cases was made by the Allegheny-Ludlum Steel Corporation according to methods that produce a high degree of preferred crystal orientation. Samples with large grains had the following composition: 3.45 per cent Si, 0.003 C, 0.008 P, 0.020 S, 0,075 Mn, 0.03I A1 and 0.072 Cu. Thickness of specimens was 0.012 inches. Plastic deformation was produced by cold-rolling the samples on a mill with 8-in. diameter rolls, the plane of the sample in each case coinciding with an XY plane (the plane of projection for the stereo-graphic plots) and the elongation occurring in the X direction. In general, elongations were held to about 3 or 4 per cent.

Jan 1, 1945

By Dorsey Lyon

INTRODUCTION THE electric furnace has always been found to be especially adapted to melting, refining, and finishing processes throughout its gradual acceptance by metallurgists, as a practical apparatus for conducting metallurgical operations. In the steel industry, the electric furnace is firmly established in the manufacture of steel of the highest grade, equal to crucible steel. For the production of the cheaper grades of steel in large tonnage, the electric furnace gives a higher-grade product than the open-hearth or converter, but due to the high cost of power prevailing in steel centers, considered from the electric furnace standpoint, it is not economical to produce tonnage steel in the electric furnace. As a refining and finishing agent for open-hearth or Bessemer steel, the electric furnace has had some degree of success in the production of tonnage steel. After a study of the use of the electric furnace in the steel industry, it appears that there may be a possibility of its use to advantage for the melting of cathode copper. In the case of copper the problem is not one of actual refining, because the copper if refined properly y the electrolytic method needs no further refining; it needs simply to be cast into a marketable shape. The name" refining". is applied to the present finishing process, because in the operation oxygen and other impurities are removed, which the electrolytic copper absorbs in being melted in the reverberatory furnace. Considering that processes may be positive, negative, and neutral; the electrolytic method would be positive; reverberatory melting of cathode copper, negative; and electric furnace melting, neutral. The electrolytic method produces about as pure a copper as is possible, if operated properly and the anodes are not too impure. The final reverberatory melting of this cathode copper lowers the grade of the final product, due to the absorption of gases and impurities.

Jan 8, 1914

By N. J. Olson, G. W. Toop

A series of equations previously derived for calculating ternary thermodynamic properties using binary data has been applied to the problem of predicting ternary phase diagrams and quaternary excess free energy. The methods are considered to be rigorous for regular ternary and quaternary systerns and empirical for nonregular systems. The equations have been used to predict ternary phase boundaries in the Pb-Sn-Zn system at 926°K and the Ag-Pd-Cu system at 1000ºK. Calculated quaternary excess free-energy values are presented for the Pb-Sn-Cd-Bi system at 773°K. A method for predicting the location of ternary phase boundaries would be a useful supplement to experimental measurements in ternary systems. This has been recognized with the considerable work that has been done to find models to predict or extend thermodynamic properties and phase diagrams in binary and ternary systems1-18 for which direct experimental measurements are limited. With the access to highspeed digital computers and mechanical plotting devices, it is currently rather easy to compare mathematical models with experimental data. The regular-solution model is consistent with systems which exhibit negative heats of mixing, positive heats of mixing, and miscibility gaps, and therefore it is applicable to simple phase diagrams. The purpose of this paper is to illustrate the use of regular-solution equations to predict, empirically, phase equilibria in some types of nonregular ternary systems. Corresponding equations for regular quaternary systems are given and used to calculate empirical quaternary excess free-energy data. METHOD FOR PREDICTING THE LOCATION OF TERNARY PHASE BOUNDARIES USING BINARY DATA Meijerin1,6 has used the regular-solution model to calculate common tangent points to ternary free energy of mixing surfaces and hence to determine phase boundaries in ternary systems involving miscibility gaps. He used the following equation to calculate ternary excess free energy of mixing values: stants characteristic of the binary solutions, and Ni is the mole fraction of component i. An alternate expression which gives for regular solutions as a function of binary values of along composition paths with constant N1/N2, N2lN3, and N1/N3 may also be derived:15 ternary r xs 1 ?c-*n.Ti*.U*. This expression for is more useful for the empirical calculation of ternary excess free-energy values for nonregular systems because actual binary AFXS data may be used in the expression rather than attempting to find suitable constants for Eq. [I]. The results of this feature of Eq. [2] are illustrated in Table I where calculated excess free-energy values for the Ni-Mn-Fe system at 1232°K are compared with experimental data of Smith, Paxton, and McCabe.19 Although regular-solution equations have been shown to give calculated thermodynamic quantities which agree quite well with experiment for single-phase nonregular ternary systems,14,15 care should be exercised in the use of the equations to predict thermo-dynamic properties of multiphase ternary systems in which strong compound formation is suspected. This precaution is consistent with the simple regular-solution model which for negative values of ai_j will indicate a tendency toward compound formation but even for very large negative values of ai-jwill not give multiphase binary or ternary systems involving a distinct stable compound. Hence, calculated ternary free-energy data using Eq. [2] might be expected to vary between being rigorous and poor, in the following order, for ternary systems which are: a) regular solutions, b) nonregular single-phase liquids in which random mixing is nearly realized, c) nonregular single-phase solids, d) nonregular multiphase systems exhibiting miscibility gaps, e) nonregular multiphase systems with binary compounds but no ternary compounds, f) nonregular multiphase systems with highly stable binary and ternary compounds. The calculated data will be expected to be least accurate for the last two cases. The general method adopted in this paper involves two-dimensional plots of ternary activity curves. The principle used is that tie lines indicating two-phase equilibria join conjugate phases a and B for example, for which a1(a) = a1(B), a2(a) = a2(B), and a3(a) = a3(B). Tie lines may be determined by plotting the ternary activities of two components along an isoactivity line for the third component and the unique points where the above equalities hold may be found graphically.

Jan 1, 1970

By R. D. Burlingame, T. L. Joseph, Gust Bitsianes

DESPITE almost fifty years of commercial practice, the sintering of iron ore has received little fundamental study. Much of the theoretical work1-'has dealt with the constitution of sinter produced under widely varying conditions. While these studies have broadened our knowledge of the changes that occur in the sintering zone and in the freshly formed sinter during the early stages of cooling, they provide little insight into the changes that precede the formation of sinter. These preliminary changes merit study as a part of the overall process. Hessle. working with beds of Swedish magnetite concentrates, was one of the first investigators to study the sintering process in its entirety. On the basis of temperatures observed at various levels of the bed during sintering, he postulated a number of distinct reaction zones to account for the chemical changes leading to the formation of sinter. A more direct method of attack is that of arresting the sintering zone after it has progressed part way through the bed. A study of a vertical cross section through such a quenched bed provides direct information on the changes taking place at various levels. This method was used by McBriar et al.' to show that several well-defined zones of chemical change existed within beds that were typical of British sintering practice. The same general method of attack was developed independently in the present investigation to study partially sintered beds typical of American practice. Experimental Sintering Equipment The sintering operation was carried out on an experimental scale with the equipment shown in Fig. 1. The refractory-walled sintering chamber A was 11 in. deep and averaged 9 in. in diameter. Air was introduced through a tapered flow section B, which contained the orifice C for accurate metering of the incoming air. This section was located directly above the square ignition housing D, which in turn rested upon the sintering chamber A. The bed was ignited with burner E. The required suction for the operation was furnished by a fan F, which had an air capacity of 500 cfm (stp). Hot exhaust gases from the sintering chamber were cleaned in the dustcatcher G before entering the exhaust fan. In the study of partially sintered beds, it was essential to find some technique for removing the entire charge from the sintering pot without disarranging the unsintered bottom portion. This problem was finally solved by sintering the charge in a removable basket, which snugly fitted the sintering chamber. This basket was constructed of two thicknesses of window screen and was lined with a 3/16-in. layer of asbestos paper. The bottom of the basket consisted of two thicknesses of wire screen, which were fastened to the basket wall. For high fuel mixtures, additional insulation was provided by a somewhat thicker layer of asbestos cement. Preparation of Partially Sintered Mixtures The moist feed was carefully placed in the sintering basket, to prevent segregation of the particles, which varied widely in size and composition. A thermocouple was placed in the center of the basket with the hot junction halfway down, and the mixture was evenly distributed around it. During ignition and throughout the sintering of the upper half of the bed, the hot junction temperature increased very little. When the sintering zone reached the halfway point, as indicated by the sudden increase in the hot junction temperature, the charge was quenched. During quenching the suction was turned off and the orifice was tightly stoppered to prevent further influx of air. At the same time, nitrogen was admitted to the sintering chamber through the orifice tap. As soon as the nitrogen had displaced the air and products of combustion, the charge was removed from the sintering pot for immediate dissection. It is impossible to preserve the exact zone structure of the bed at the instant that combustion is arrested unless the downward transmission of heat is also immediately stopped. Fortunately, heat transfer is very slow in beds containing a stationary fluid, especially if the particle size is small. It follows that the minimum quantity of nitrogen should be used to displace the air and that static conditions be established as soon as possible. A very steep temperature gradient across the combustion zone for some time after the quench was evidence of in-

Jan 1, 1957

By Lawrence A. Roe

The magnetic reflux classifier, which utilizes the combined effects of magnetic fields and a hindered settling classifier, is a new tool for determining the quantity and quality of middlings in fine-sized magnetite concentrates. Results are given for processing a typical taconite ore, and a sketch of the apparatus is included. IN examining magnetite ores and beneficiated products it often becomes necessary to make critical studies of the amount of grinding necessary to produce the desired degree of magnetite liberation. In the past this has been accomplished by laboratory heavy-liquid tests, which provide a method for selectively removing middling particles and free magnetite from various-sized fractions. Examination of the various products under the microscope results in fairly accurate determination of the degree of liberation. The method is quite efficient on sizes coarser than 325 mesh. Thus the heavy-liquid method of middling separation was satisfactory until the advent of present day magnetic taconite studies. When magnetite concentrates ranging from 70 to 100 pct —325 mesh are studied it becomes apparent that older methods of determining liberation size are not satisfactory and that there is need for a new method. For example, some of the low-grade magnetite ores of the Wisconsin and Michigan iron ranges require grinding to 100 pct —325 mesh to produce a magnetic concentrate containing less than 12 pct silica. Examination of concentrates from such ores often reveals that many of the middling particles consist of only very minor proportions of iron mineral. Thus it becomes important to be able to determine the degree of grinding necessary not only for complete liberation, but also for liberation of only 80, 85, or 90 pct of the total iron mineral content. Actually, complete liberation is never attained, but is often used to designate that degree of liberation necessary for production of high-grade concentrates. A rougher concentrate, produced after elimination of a coarse-sized tailing, can usually be subjected to a second grinding stage and concentrated into a higher grade product than could be produced from the same crude ore with one stage of grinding resulting in the same overall size reduction. This fact adds to the importance of being able to determine partial degrees of liberation on any magnetite ore. Standard laboratory methods such as heavy-liquid separation, microscopic grain counts, Davis tube magnetic separation, magnetic flocculation, classification, flotation, and others often are not applicable, or are prohibitive because of time requirements when large numbers of fine-sized magnetite samples are investigated. The Davis tube magnetic separator is an efficient tool to use in rejecting the non-magnetic mineral particles from an ore sample. The middlings discarded by the tube separator usually are so low in iron content that they can be considered relatively unimportant in liberation studies. This condition is caused by the extremely high flux density used in the Davis tube. This flux density ranges from four to eight times the flux density produced by most of the powerful commercial machines in use today. Thus the problem resolves itself into a search for a method of selectively removing middlings from Davis tube magnetic concentrates which will be both rapid and efficient. Those methods showing most promise in the development of a process for isolating middlings from extremely fine-sized magnetic concentrates were flotation and magnetic flocculation. The use of flotation to remove middlings from magnetic concentrates is reported in the literature.'.' The flotation process is effective in removing middlings from a magnetite concentrate, but physical entrapment of fine-sized free magnetite in the silica-bearing froth is an undesirable feature. The flotation method of removing middlings requires time, effort, and precise control of many variables, and does not meet the required degree of middling isolation. Magnetic Flocculation Magnetic flocculation has long been resorted to"-" in efforts to upgrade magnetite concentrates. One of the new magnetic taconite plants now under construction on the Mesabi Range includes magnetic flocculation in the flowsheet' as an accessory process to remove high-silica middlings and free silica which has been mechanically entrapped in magnetite flocs. The use of magnetic flocculation as a laboratory method of making precise separation of middlings was further investigated, since it offered a rapid, simple method of accomplishing the desired result. Magnetic flocculation involves the subjection of a magnetic concentrate to a strong magnetic field, passing the concentrate in a highly flocculated condition to a hydroseparator or other classifiers of various types, and removing free silica and middlings as overflow products. In an attempt to utilize simple

Jan 1, 1954

By Walter Mathesius

The use of high blast heats on furnaces melting Mesaba ores is still the exception, the average blast temperatures carried on Mesaba stacks seldom reaching 1,100" F. Some 15 years ago, when the use of fine Mesaba ores in larger proportions to the total burden first came into practice, it was found difficult to employ even those blast heats which it had been possible ' to carry with the Old Range ores. The furnaces refused to "take" high heats, and would persistently labor with irregular stock movement, which impaired the practice and increased the coke consumption. By lowering the blast temperature, the working of the furnace became smoother, and experience taught that with the softer and more easily reduced Mesaba ores, satisfactory practice could be obtained with comparatively low blast heats. Therefore a large number of Mesaba furnaces have ever since been operated on very low blast temperatures, ranging between 800" and 1,000" F. In the face of these difficulties, furnace men were slow to recognize that furnaces could be so designed as to permit a free movement of the charges in combination with the use of higher heats. Since higher blast temperatures did not seem to offer great advantages in the smelting of Mesaba ores, investments in hot-blast stoves were not as attractive to the furnace man as labor-saving devices and means of obtaining greater tonnages. The effect of this preference is keenly felt at the present time. It has brought about the peculiar situation, that the majority of our furnace plants (among them some of the most progressive) lack modern and efficient stove equipment. The result is that, even where the proper furnace lines have been adopted and conditions are now favorable to the successful employment of higher blast temperatures, the heats required for the greatest fuel economy are not available. In an endeavor to obtain results, even with inadequate equipment, we find that, at many plants, the stoves are worked far beyond their capacity. This leads, in many instances, to a situation in which the coke saving in the

Jan 1, 1915

By Thomas C. Wilder, Walter E. Galin

Measurements of the electromotive force of the cell at 995°C have shown that the cell may be used to detennine the zinc content of molten Cu-Zn alloys to the nearest 0.05 wt pct. The cell is used for brass melts to which no ZnO is added intentionally, because essentially all oxygen in the Cu-Zn-O system is present in the form of ZnO. The cell is also used to detev,nine the thernodynamic activity of zinc for Cu-Zn al1oys of the brass composition range, from which the equilibrium partial pressure of zinc for such alloy may also be calculated. The electrochemical measurement of the concentration of the most active metal in other engneering- alloy systems by a similar technique is also considered. IN recent years there have been many studies concerning the direct electrochemical measurement of oxygen content in molten engineering metals.' These investigations employ galvanic cells in which the electrolytes are various solid mixed-oxides which conduct current by movement of oxide ion vacancies under the influence of an oxygen potential gradient. Similar cells have also been used to measure the thermodynamic properties of mixing of solid alloys,' one component of which has a much greater affinity for oxygen than the other component(s). One alloy system of obvious engineering importance comprised of two metals of greatly differing affinity for oxygen is copper-zinc. At the casting temperature of molten brasses, the zinc concentration is very difficult to control not only because its vapor pressure is very high, but also because of its high affinity for oxygen to form ZnO. Inasmuch as brass castings may be required to have a zinc concentration within very narrow limits, it would be advantageous for the brass industry to have a means for quickly measuring the zinc content in the molten alloy just prior to pouring. A calculation based on earlier thermodynamic studies of oxygen and zinc in dilute solution in binary Cu-O and CU-Z' alloys indicates that the oxygen concentration of molten 70 wt pct Cu-30 wt pct Zn brass must be much less than 1 ppm for the separate phase ZnO not to exist in the ternary Cu-Zn-O system. Thus it can be assumed that all molten brasses, both in the laboratory and in the foundry, are sufficiently saturated with oxygen for the separate phase ZnO to be present. In view of the foregoing reasons, the cell investigated at 995°C for the purpose of measuring the zinc concentration in molten copper-zinc alloys, particularly those of brass compositions. In this cell the left hand electrode is a reference electrode comprised of a mixture of the pure powders of nickel and nickel oxide, to which a platinum contact is made. The electrode of interest is a molten Cu-Zn alloy of unknown zinc concentration with a tantalum wire contact. The electrolyte is the commercially available (Zircoa) calcia stabilized zirconia. The ZnO in the Cu-Zn electrode compartment is not intentionally added, but is naturally present as a result of the infinitesimal amount of oxygen required for its formation in this alloy system. In cell [A] nickel oxide is reduced at the cathode where O= represents the electrolyte. At the anode dissolved zinc of the Cu-Zn alloy is oxidized to form ZnO(s) in its standard state Thus the overall reaction is for which the molar free energy change is where 5 is the Faraday equivalent (23,063 cal per v equivalent), is the electromotive force of the cell in volts after correction for the Pt-Ta thermocouple, FOf (ZO) and AFF (NO) are the standard molar free energies of formation of the respective oxides, and a2n is the thermodynamic activity of zinc in the molten Cu-Zn alloy. The reference state of zinc in this case is taken to be the pure liquid. At constant temperature all the terms of Eq. [I] are constant except and azn Thus since all other participants in the electrochemical reaction are in their standard states, the change in the electromotive force of Cell [A] is represented only by a change of the thermodynamic activity of zinc at constant temperature. The zinc concentration is related to the activity by sampling the alloy for chemical analysis after cell measurements are taken. EXPERIMENTAL A typical cell construction is shown in Fig. 1. This and other experimental details were similar to that described earlier with the exception of some minor modifications which are detailed below.

Jan 1, 1970

By H. W. Straley

Some ten years ago the writer1 made a survey of college catalogues to determine what sort of training geologists were receiving in basic sciences. In the light of this compilation and subsequent experience, he made the statement at the 1939 meeting of the Institute that apparently only in schools offering a curriculum in geological engineering or in the geological option of mining engineering curricula could geologists hope to receive the training advocated by Hubbeet.2 In the former study, schools of engineering were excluded because the preparation was known beforehand. The present study aims to consider engineering schools in an effort to determine not only what basic studies are required but what use is made of them in geological courses of the third and fourth years. The present study combined the method of consulting catalogues with a questionnaire. Letters were mailed to officials responsible for supervision of mineral industries curricula requesting information On' (I) the extent to which the engineering preparation of the first two years is actually used in the work of the last two; (2) the extent to which the engineering of the last two years is used in courses in geological engineering or geology; and (3) whether geologists or geological engineers teach descriptively or analytically. Both methods of securing information are open to criticism; the former on the basis of the incomplete information supplied by university catalogues concerning prerequisites and curricula and the latter on the ground that the questions may be phrased poorly or given insufficient consideration by replying officials. Fifty-six questionnaires were mailed and 39 (70 per cent) replies were received. Of the replies, 6 (11.3 per cent) were from colleges of liberal arts unconnected with engineering schools, 11 (20 per cent) were from schools having curricula in geological engineering and 22 (39 per cent) were from departments of mining engineering. The number of replies and their distribution were satisfactory in spite of the receipt of only six from liberal arts colleges. It should be understood that the universities of which the catalogues were examined were not necessarily the same in both compilations. No departments that are admittedly or known to be acting solely as service departments were recorded in the second study. Table I shows that all professional schools require mathematics through calculus, whereas only 7 per cent of the liberal arts curricula expect the same level of preparation; only 73 per cent require trigonometry and 40 per cent college "algebra. The proportion of geological engineering curricula requiring differential equations is higher than mining. All of the engineering schools require general and analytical chemistry, whereas only 77 per cent of liberal arts curricula require general and 18 per cent analytical. Twenty-two per cent of the mining and 40 per cent of the geological engineering

Jan 1, 1946

Surface mining of coal is widely condemned as a despoiler of the countryside and wastrel of land and natural resources. Yet the fact has been as widely ignored that the ingenuity of those engaged in developing the methods and equipment utilized in surface mining have made several hundred million tons of coal available for utilities and industry which could never have been mined by any other method. While doing this, the surface mining companies have recovered nearly 100% of the coal in the mining area instead of approximately 50% as is common in underground methods. Efficiency has been increasing constantly, thereby maintaining low cost to the customer. Mining has provided economic health in many areas by virtue of the direct payrolls and by the attraction of other industries to enjoy low cost, dependable fuel supplies. Surface mining of coal generally falls into two categories: contour mining, which is the result of mining in hilly or mountainous terrain where the hillside or slope limits the width of the area which can be surface mined; and area mining, which results from the surface of the land being approximately parallel with the coal seam so that a wide area may be mined in a succession of pits or open cuts.

Jan 10, 1972

By H. H. Wade, N. F. Schulz

The large quantities of iron-bearing materials, including taconite, semi-taconite,* and other low-grade ferruginous materials occurring in Minnesota and elsewhere, constitute an important potential source of iron. Satisfactory grade and recovery of iron ore concentrate cannot ordinarily be obtained from these ferruginous materials by simple methods of beneficiation. Iron is distinctive in that the free metal and two of its oxides [magnetite (Fe2O3) and maghemite (gamma-Fe2O3) ] are strongly ferromagnetic. The successful magnetic separation of natural magnetite from taconite has already been established on a commercial scale. The iron in semi-taconite, however, occurs largely as goethite (Fe2O3-H4O) and hematite (Fe2O3) which do not respond to ordinary magnetic separation methods. Magnetic roasting converts these iron oxides to magnetite, which can, after liberation, be magnetically concentrated. MAGNETIC ROASTING Hematite undergoes a stepwise reduction when exposed at moderately elevated temperatures to a reducing atmosphere containing hydrogen or carbon monoxide: Fe2O3? Fe3O4 ? FeO ? Fe Since the desirable product in magnetic roasting is Fe3O4, the conversion is halted after the first stage by controlling the reduction potential of the gas mixture with water vapor or carbon dioxide. The reducing gas mixture must be such that the oxygen partial pressure at the solid-gas reaction interface will be maintained intermediately between the oxygen partial pressures in equilibrium with Fe2O3 and Fe3O4 at the prevailing temperature. Because of the rapid increase in decomposition pressure of Fe3O4 with increase in temperature, the practical upper limit of useful reaction temperature is about 1400°F, above which over-reduction usually occurs in atmospheres containing hydrogen or carbon monoxide. On the other hand, useful reaction rates usually occur only above 800°F. Goethite reacts similarly except that the combined water probably has to be driven off thermally before the reduction to magnetite occurs. Iron carbonate must also be decomposed thermally to an oxide before conversion to magnetite. Iron silicates are apparently not amenable to magnetic roasting. The rate of penetration of the reaction toward the interior of a given ore fragment is dependent on the chemical composition and physical structure of the solid. Most ore fragments tested here reduced satisfactorily to 1/4-in. depth in less than 14 min at 1200°F. Some very dense fragments, however, were reduced to less than 1/32-in. depth under the same conditions. Determination of the optimum temperature, gas composition, ore fragment size, or time of exposure

Jan 1, 1961

Jan 1, 1947

By J. S. Aronofsky, J. P. Heller

This paper presents a mathematical analysis of the fluid mixing which occurs during flow through porous media. The analysis is based on the well-known diffusion equation with mass transfer term. It is pointed out that the use of this equation is justified by a single general assumption which does not specify any particular mechanism for the mixing process. Formulas are given for tracer fluid concentrations for two different boundary and initial conditions. Calculated numerical values compare closely with some published results of experiments in which no viscosity or density difference existed between displaced and displacing fluids. INTRODUCTION A phenomenological theory of the mixing and diffusion process is presented for the flow in a porous medium of two miscible liquids of equal viscosity and density. This is based on the classical diffusion equation which has been used to explain such processes as Brownian motion and heat conduction. More recently, this same differential equation has been derived (in a manner analogous to the work in this paper) for the problem of heat transfer during fluid flow in porous media.' The purpose of this paper is to show that the available experimental evidence justifies the use of this simple diffusion equation. The recent data of Koch and Slobod' and of von Rosenberg' are used to test this diffusion model by comparing concentration curve shapes and calculating "effective diffusion coefficients". The same differential equation for miscible displacement, as well as some experimental confirmation, has been published in Japan by K. Yuhara,4 and recently in this country by Day.5 Yuhara arrives at his con-clusions through analogy with turbulent diffusion, de- scribing the microscopic velocities in terms of "eddy motion" — although unlike the ordinary eddies of hydraulics. Day proceeds directly from Scheidegger's6 concept of the dispersion of velocities. After a very clear description of Scheidegger's theory, he applies it to calculate the motion first of a drop and then of a thin layer of brine into a bed of sand. For the latter case, Day derives and solves the same differential equation as Eq. 1. In our presentation no detailed assumptions are made as to the mechanism of displacement. In fact, several microscopic processes may well be involved—the only general assumption made is that their cumulative microscopic effect may be described by the addition of a second-order term to the differentirl equation of continuity. DERIVATION OF EQUATIONS Let us consider the displacement in one spatial dimension of Liquid A from a sample of porous media by Liquid B. A and B are assumed completely miscible and of the same viscosity and density. Both fluids are also assumed to be incompressible and it is specified that the total flow is the same for any cross section. It is evident that the rate at which Liquid B would be carried across such a section would be given by the product of the fluid velocity, u, and the concentration, C, of B in the fluid mixture assuming the constancy of u and C over the cross section. Since the volume of Fluid B is conserved, this leads to the one-way wave equation - u ?C/?x = ? ?C/?l where x increases in the direction of u—the "Darcy velocity", Q/A (or velocity flux per unit area), and 9 is the fractional porosity. Consider the case where fluid B is displacing Fluid A and the concentration distribution is represented by a step funcLon (with a vertical discontinuity). The solution of Eq. 1 predicts no mixing

Jan 1, 1958

By Noel H. Stearn

When the Age of Machinery was suddenly thrust upon civilization about the beginning of the 19th century, an unprecedented demand for mineral resources sprang up. This demand brought about the rapid development of the known ore deposits and the discovery of such other deposits as could be encountered by energetic and canny prospectors. Thus in the countries now reasonably accessible nearly all orebodies have been located except those which are totally concealed even from the eyes and "senses " of experienced and expert prospectors. The high rate of exhaustion of known ore deposits and the necessity of looking farther and farther ahead for raw materials as a matter of insurance on the stupendous capital outlays involved in mining, development, and conversion operations, have resulted in exceptional activity in three different fields of effort. The first is purely geographic. Prospectors are now penetrating the few hitherto inaccessible regions in the hope of stumbling upon exposed ore deposits or locating visible indications of their presence. The second is chemical. Industrial chemists and metallurgists are seeking to facilitate the exploitation of lower grade ores or to find methods of recovering valuable metals from common substances. In the third field of effort lie the activities of the economic geologist and the mining engineer, who endeavor to locate concealed ore deposits which would remain hidden from the prospector no matter how expert or conscientious he might be. Obviously the task which such a man must face is both exacting and indefinite, and the tools which he has heretofore been permitted to bring to it are, for the most part, abstract—a knowledge of certain fundamental principles and processes involved in the origin, occurrence, structure, and distribution of deposits of natural resources and of the rocks which form the environments of those deposits; and a process of reasoning by analogy supplemented by the use of the diamond drill, or such artificial exposure as the test pit, trench, shaft, or tunnel.

Jan 1, 1929

On request of the Commissioner of Education, a small group of administrative professors of engineering and commerce from higher institutions near St. Louis met in conference with the Specialist in Commercial Education of the Bureau of Education on Feb. 22, for the purpose of discussing ways and means whereby the business of our country may be furthered through increased opportunity in our higher institutions for the preparation of engineers with business training. One or more representatives were present at this conference from the University of Minnesota, University of Illinois, Washington -University, University of Missouri, University of Iowa, Iowa State College, University of Kansas. It was recommended at this conference: First, That the Commissioner of Education appoint immediately a committee to consider commercial engineering in its various aspects and to prepare and approve one or more curricula in commercial and industrial engineering that can be recommended by the Bureau of Education for adoption in our colleges and universities. It was suggested that the committee consider the following curricula plans: First, That a minimum number of hours in business training be required in all engineering courses. Second, That a curriculum providing for a minimum of fifteen to thirty units in business economics be incorporated in all engineering courses and offered on an elective basis. Third, That a curriculum in commercial or industrial engineering, permitting full and proper emphasis upon engineering subjects, be offered in the School of Commerce with degree to be given in that school. Fourth, That a five-year combined engineering and commercial course he prepared.

Jan 5, 1919

By David White

Attention has been given to the sources and supply of the raw vegetal matter and the conditions of its submission to the process of sedimentation. An original and most valuable review has been made of the more important or significant chemical compounds originally contained in the organic dct,ris, and of the biochemical changes undergone by the latter during deposition. Consideration also has been given to the factors controlling the selective biochemical decomposition, in whole or in part, of this debris, and the deposition, as sediments, of the undecom-posed plant structures and compounds, together with more or less of the so-called "ulmic," or "humic," organic decomposition products in colloidal so1ution. Biochemical Changes End in Peat Formation The biochemical process terminates in the peat stage of coal formation, and with the cessation of this process organic sedimentation is completed. All subsequent changes result from geological causes and conditions. The deposits are in the form of peats of different types, organic muds, oozes, etc. They are essentially uncompressed and are wholly uncon-solidated, and their water content is great, amounting to over 85 per cent, near the surface of the deposit. Many of the chemical compounds remain as in the once living organisms; others are biochemically broken down and new ones formed. Geochemical and Geophysical Changes in Buried Deposits Subsequent Changes " Dynamochemical" The changes which subsequently take place through dehydration, lithification, and simultaneous progressive chemical alteration, by which organic sediments are advanced to brown lignite, subbituminous, bituminous, semianthracitic, and graphitic ranks, are geochemical and geophysical, and the process, which really is metamorphic,2 takes place under dynamic influences. In fact, the essential changes, including loading,

Jan 1, 1925

By P. H. Strickland, F. Lawson

It is now well established that in the majority of cementation processes used industrially, the rate of reaction can be described in terms of the mass transport from the bulk of the solution to the deposition sites on the metallic surface. Thus it should be possible to design cementation equipment from a knowledge of the flow situation in the equipment, and of absolute kinetic data. One way of obtaining such absolute data is by the use of the rotating disc geometry; this geometry is particularly suitable for a detailed study of cementation reactions. In spite of the similar mass transfer mechanism, cementation processes differ from other ionic transport processes in at least two respects. The presence of an attached deposit generally has a significant enhancing effect on the reaction rate; and side reactions involving oxygen and/or hydrogen ions can completely change the course of a reaction. Investigation of these peculiarities is necessary for a complete understanding of the process; since they cannot be isolated from the basic mass transport mechanism, close control of experimental conditions is essential. It has been found that the enhancement in deposition rate persists even when the deposit reaches a thickness several times that of the transport boundary layer thickness on the smooth surface. An explanation of the enhancement in reaction rate is proposed.

Jan 1, 1973

By J. S. Fulton

Those who live in steel-mill towns are so accustomed to the sight of flames spouting from the mouth of a Bessemer vessel that they seldom pause to think of the amazing process behind it. Actually cold air is being blown through a hot liquid and, instead of cooling it, raises the temperature of the liquid. When coffee is too hot to drink, we know that blowing on it will cool it, so it was no wonder that when Henry Bessemer (or William Kelly, as your patriotism chooses) first proposed this cycle of steel production, he was considered mad. When Bessemer and Kelly started their investigations around 1852, there was not much practical knowledge of metallurgy and, in consequence, there was wide variation in the product made by their process. It was appreciated that the silicon, carbon and iron were all potential fuels, but not until Mushet discovered the beneficial effects of having manganese in the pig iron did the process really become commercial. Bessemer's patent of 1855 covered a crucibleful of liquid iron into which a refractory tuyere was lowered and the blow started. Since that time virtually every conceivable form of vessel, bottom arrangemerit, tuyere size and location have been suggested or tried. There have been stationary vessels with fixed bottoms, that were side, top or bottom blown; tilting vessels with two sets of side tuyeres at different elevations; vessels like a three-compartmerit septic tank; vessels of a cylindrical form supported on the long axis with tuyeres along the side submerged by a partial rotation of the vessel (this type continues in copper refineries); portable vessels to make the blow in a ladle over a mold in a foundry; a combination of a cupola and converter in one shell, and various other arrangements. But in all these experiments, compressed air for the blast was presupposed and there was little discussion of the quantity or quality of the air delivered to the tuyeres. At one time or another various practices that now are forgotten have been tried or suggested: for instance, the use of inert gas at the end of the blow; the addition of fuel to the blast; the use of hot-blast stoves; the drying of the air to a minimum moisture in the blast. Except in the last-named method little attention was paid to the quality or quantity of the air blown. Phases Of the many Papers published On various phases of the Bessemer process, nearly '7' according to one bibliography, Over go per 'ent were concerned with the metallurgical phase and less than '0 per cent discussed various sections of the pneumatic phase. Since the two phases are coincidental, apparently nine times as much thought has been given to the result as has been given to One of the causes of the Bessemer process. IS it not possible that if more attention had been paid to the pneumatics so many papers would not have had to be written on the troubles in the metallurgical phase? A study of published papers and conversation

Jan 1, 1941

By John V. Beall

The forecast of continued growing demand for phosphate, chiefly for fertilizer, has caused a world-wide rush for deposits by a variety of companies many of which have never before mined phosphate rock. The newcomers are diversifying into this growth industry on the strength of certain capabilities. Among these are the availability of investment capital, mining or processing know-how and marketing experience. Product tie-ins have motivated some into the search. Companies with excess sulfuric acid or potential for making it are in this category. This acid is the most commonly used for dissolving phosphate rock to make phosphoric acid. Base metal smelting companies are prime candidates in this field with by-product acid from roasting processes. Producers of "sweet" natural gas, such as those in Louisiana and Texas, have a potential for recovering low cost hydrogen from excess gas production for the manufacture of ammonia, the main source of nitrogen for fertilizer. "Sour" gas producers, such as those in the Canadian fields, are making sulfuric acid that is combined with western U.S. phosphate to make fertilizer materials. The presence of one or two steel companies in the look-see for phosphate deposits is based on by-product ammonia from coke-oven gas.

Jan 10, 1966

By C. A. Hartinagel

During 1941, the total production of crude oil in New York state was 5,185,000 bbl. This represents a small increase over the average for the past five years. From 1921, when the annual production of the state amounted to only 988,000 bbl., there was a regular annual increase in production (excepting one or two years) until the 5,000,000-bbl. mark was reached in 1937, After more than 20 years of oil recovery by flooding methods, it was generally believed, until a few months ago, that the rate of production was nearly at its peak and within a few years the fields would experience a gradual decline as the thicker sands became exhausted and the thinner ones could be worked only at increasing costs. As a result of the present emergency, however, unusual efforts are being made, in spite of higher costs of operation, to increase the output of Pennsylvania grade oil, to which the New York product belongs. Since most of any increased production would be obtained by flooding, and since floods travel slowly, no large increase in production can be expected for some months to come. During the first year, 10 or 15 per cent increase could be obtained, but maximum production, an increase of perhaps 40 per cent, could not be expected until some time during the second or third year. In the Allegany fields, which account for two thirds of the state's oil production, 1246 wells, including water-intake wells, were drilled during the year; 390 more than in the preceding year and 590 more than in 1939. It is evident that much of the best oil territory has already been developed. As producers move toward edge properties and thinner sands, returns will be smaller, whereas costs remain the same or, under war conditions, become higher. It is estimated that at least 60 million barrels of oil is in sight and will be produced from the thicker sands by present recovery methods. In the thinner sands and edge properties, some 35 million additional barrels can be produced at a profit only if prices become higher. In view of the fact that there is little hope of finding new oil pools in New York, one of the future problems of the oil producer will be to obtain adequate returns for increased production costs. The year started with a posted price of $2.15 per barrel of crude. There were five successive price increases until the high of the year was reached at $2.98 on Aug. 14. Eight days later the Office of Price Administration directed that the price be reduced to the June level of $2.75 a barrel, which remained in effect to the end of the year. With rising costs of operation, it is feared that many of the smaller properties cannot continue production unless the Federal price cut is revoked. During the year, Allegany Refiners Inc., a local enterprise founded in 1933, with plant at Bolivar, western Allegany County, increased its refining capacity from 1000 to 1500 bbl. daily. At the same time equipment was added to make the plant a complete lubricating-oil refinery, including facilities for the refining of wax into the finished product. Previous to the enlargement, it was necessary to sell the wax

Jan 1, 1942

R. C. Canby, Wallingford, Conn. (communication to the Secretary*). —Apropos of the experimental reduction of copper from cuprous chloride by fusion with ground limestone and colre, as described by Messrs. Laist and Frick, and also proposed for use at Chuquicamata, it might be of interest to refer bricfly to the experience at Argentine, Kan., in the smelting of the suboxide of copper (as produced in the Hunt and Douglas process) containing appreciable quantities of chlorides. In the Engineering and Mining Journal of June 10, 1911,I gave some account of what had appeared to be crucial difficulties with the Hunt and Douglas process, and how the filter-press difficulty had been so rapidly overcorne after my discovery of the effect of the sodium salts in the leaching solutions. I also described the effect of the cupola-furnace gases upon the lime rock with which I had replaced the coke in the absorption tower, which apparently showed the presence of considerable chlorine, due to the imperfect conversion of the subchloride to suboxide, as well as that due to the difficulties of washing thoroughly the suboxide with the means provided, and also to the presence of chlorides in the cement copper which was smelted with the suboxide. The fumes from the cupola, when issuing direct into the atmosphere, were very dense and white, except when a hot furnace top caused a reddish tinge due to dust. These fumes had a peculiarly suffocating effect, SO that when they were blown over into the town the population suffered the greatest actual distress, not the mere annoyance which would have been due to a disagreeable odor. The absorption tower had been built at the instance of the city authorities to abate this nuisance, and not with the idea of making any additional metal savings. A serious feature in connection with the Argentine experience with the Hunt and Douglas process was, that it had been implicitly assumed that there could be no metal loss in the Hunt and Douglas process itself, and that all attempts to locate the ruinous copper losses which were accumulating in the metallurgical accounts were devoted to the roasting department. It is possibly unfortunate for metallurgical advance along these particular lines that just about the time of this discovery of this previously unsuspected volatilization loss, in the smelting of the suboxide, the Kansas City company made a contract with the Western Union Telegraph Co. for its supply of copper sulphate and the Hunt and Douglas

Jan 1, 1915