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By N. Arbiter, C. C. Harris

In 1961, a research program started at Columbia into the mechanical aspects of flotation,* and certain ends are now in view. The purpose of this note is to explain these tentative conclusions in the hope of stimulating discussion and eliciting new data, especially industrial data, with which to test the views expressed. The variables presently under consideration are impeller rotational speed, N, volumetric air rate, Q, and impeller diameter, D, the latter being the parameter chosen to designate cell size. The most favorable *The latest work 1 references all previous publications. chemical environment is not under discussion since the procedures for establishing it are better understood than those for optimizing N and Q by virtue of a longer history of more intensive investigation. THE GRADE AND RECOVERY SURFACES With a given ore, chemical treatment, and flotation machine, both grade, G, and recovery, R, are functions of N and Q. The GNQ and RNQ relationships are best viewed in terms of three-dimensional surfaces (Fig. 1) which are experimentally determinate.2 TO maintain grade at an acceptably high level, it is necessary for N and Q to lie within certain limits, and similarly with recovery. However, the ranges of N and Q for grade on the one hand and recovery on the other are rarely the same. Selecting the single N

Jan 1, 1970

By E. W. Newman

During 1943 and 1944, there was an urgent need for certain grades of optical calcite (Iceland spar) for instruments for ' military uses. To find a supply of this material, prospecting was carried out in Montana, California and Colorado. Although some production was obtained by the work in California, the best results were from prospecting the large calcite veins of south central Montana. The bulk of the optical calcite mind during World War II has come from that area. The Bureau of Mines took an active part in the search for optical calcite in Montana. It examined most of the known calcite veins in the 70-mile distance between Wilsall, on the Shields River: and Absarokee, on the Still water River, and conducted exploration on several of the deposits. The Geological Survey also took an active part by mapping many of the veins. Actual mining of the calcite was performed at first by Calcite Operators, Inc., and later by the Metals Reserve Co., through an agent. A sorting plant was established at Clyde Park, where custom material could be sold. These activities stimulated mining by private operators. To be suitable for military uses, the calcite mined had to meet rigid specificstions as to both size and quality. Individual crystals had to be clear and transparent and if in the form of rhombs had to measure at least 7/8 in. on each edge. Some color and a few inclusions in the calcite were allowable, but material with incipient or developed cleavages, or showing twinning other than parallel to the base, was unacceptable. History of Deposits The existence of large veins of calcite in south central Montana has long been known, and for many years the farmers of this region have used the common vein calcite for producing grit for chicken feed. According to reports, the fist optical calcite produced from Montana came from the Cartwright deposit near Grey-cliff,' but until recently the mining of optical calcite in Montana has been limited to spasmodic searching for small crystals suitable for making nicol prisms for saccharimeters and microscopes, or for mineral specimens. The possible need of substantial amounts of optical calcite for military uses began to appear late in 1942 and early in 1943, therefore the Polaroid company began searching for a source of supply in Montana and California. Work on the Wade property near Clyde Park was started on a small scale in the fall of 1942, by .4. H. Hansen, of Clyde Park. During the winter and spring of 1943, a modest quantity of optical calcite was mined and shipped to the Polaroid Corporation, Cambridge, Mass. Most of this was produced from the "Hansen vug," which was found close to the surface. Early in the summer of 1943, mining on the Wade property was undertaken by Calcite Operators, Inc., a company organized for mining optical calcite from the

Jan 1, 1948

By E. W. Newman

During 1943 and 1944, there was an urgent need for certain grades of optical calcite (Iceland spar) for instruments for ' military uses. To find a supply of this material, prospecting was carried out in Montana, California and Colorado. Although some production was obtained by the work in California, the best results were from prospecting the large calcite veins of south central Montana. The bulk of the optical calcite mind during World War II has come from that area. The Bureau of Mines took an active part in the search for optical calcite in Montana. It examined most of the known calcite veins in the 70-mile distance between Wilsall, on the Shields River: and Absarokee, on the Still water River, and conducted exploration on several of the deposits. The Geological Survey also took an active part by mapping many of the veins. Actual mining of the calcite was performed at first by Calcite Operators, Inc., and later by the Metals Reserve Co., through an agent. A sorting plant was established at Clyde Park, where custom material could be sold. These activities stimulated mining by private operators. To be suitable for military uses, the calcite mined had to meet rigid specificstions as to both size and quality. Individual crystals had to be clear and transparent and if in the form of rhombs had to measure at least 7/8 in. on each edge. Some color and a few inclusions in the calcite were allowable, but material with incipient or developed cleavages, or showing twinning other than parallel to the base, was unacceptable. History of Deposits The existence of large veins of calcite in south central Montana has long been known, and for many years the farmers of this region have used the common vein calcite for producing grit for chicken feed. According to reports, the fist optical calcite produced from Montana came from the Cartwright deposit near Grey-cliff,' but until recently the mining of optical calcite in Montana has been limited to spasmodic searching for small crystals suitable for making nicol prisms for saccharimeters and microscopes, or for mineral specimens. The possible need of substantial amounts of optical calcite for military uses began to appear late in 1942 and early in 1943, therefore the Polaroid company began searching for a source of supply in Montana and California. Work on the Wade property near Clyde Park was started on a small scale in the fall of 1942, by .4. H. Hansen, of Clyde Park. During the winter and spring of 1943, a modest quantity of optical calcite was mined and shipped to the Polaroid Corporation, Cambridge, Mass. Most of this was produced from the "Hansen vug," which was found close to the surface. Early in the summer of 1943, mining on the Wade property was undertaken by Calcite Operators, Inc., a company organized for mining optical calcite from the

Jan 1, 1948

By Joseph J. Yancik, Leonard L. Felts, George B. Clark

Little information has been published concerning the actual or useful amount of energy obtained from explosives when they are used for blasting. To provide more data on this subject, 8-in. neet cement cubes were blasted in a steel plate box and the breakage energy evaluated by comparison with drop crusher results using Rittinger's," ' Kick's,%nd Bond's' theories. Theories by Bond and Wang," Lineau,' Hatch,' Roller," and others were not considered applicable. Those used in this investigation may be expressed mathematically as follows: [ ] The above equations were employed to determine values of KK, K for particle size distributions similar to those obtained from the blasting curves. These values were in turn used as a means of approximating the specific energy of the blasted material. The efficiency of crushing by blasting was then determined by dividing this specific energy by the maximum available work of the explosive per gram of cement.

Mar 1, 1956

By David Scott

WHEN mining operations were first instituted in the mines of the Miami Copper Co., at Miami, Ariz., the relatively hard character of the ground in the western section of the property made it seem advisable to use a wide shrinkage stope and pillar system. The system as finally evolved was applied to the mining of 2,300,000 tons of ore by the use of stopes and pillars each 50 ft. in width. Development, mining and extraction of this reserve has been continuously in progress since 1910, and the final stages of extraction are now reached. A complete survey of all phases of this system can therefore be made. Modification in working methods was obviously necessary, and the system to be described is believed to be typical of the best features. DEVELOPMENT The preliminary work had three main objectives: The opening of a haulage level, the construction of a drawing-off level, and the driving of sublevels for use in stoping. In addition to these, some extra sublevel drifting was necessary to determine exactly the boundaries of the orebody, the general outline having been determined by churn drilling. This development was based on the requirements of stopes 50 ft. wide, with pillars 50 ft. wide between each stope. The length of these units varied from 200 to 500 ft.

Jan 6, 1916

By R. P. Carreker

THE experiments described in this report were conducted as a part of a general program designed to document the deformation behavior of pure metals over a wide range of temperature. Material The silver used in this investigation was obtained from the Handy and Harmon Co. as 99.97+ pct pure. It is from the same length of wire as that designated H-H silver by Hoffman and Turnbull in their investigation of self-diffusion in silver.' The silver was drawn at room temperature from 0.060-in. diam to 0.020-in. diam wire without intermediate annealing. Seven-inch lengths of cold-drawn wire were annealed in groups of ten by placing them in individual quartz tubes spaced circumferentially about and near the vertical furnace axis. Dry nitrogen was passed through the furnace to lower the partial pressure of oxygen. The three annealing temperatures used were 700°, 800°, and 900°C, producing grain sizes of 0.017, 0.040, and 0.250 mm diam after 30 min at temperature. Testing Procedure The details of the testing procedure have been described in the reporting of results of a similar investigation of Copper. Annealed specimens of 5-in. gage length were gripped between grooved plates. Tests were performed using an Instron tensile-test-

Jan 1, 1958

By Cyril Stanley Smith

BeTa brass (consisting of approximately equal atomic proportions of copper and zinc) exists as a random solid solution at high temperatures, hut at low temperature< an ordered structure is stable, with the copper and zinc atoms occupying alternate sites on the body-centered-cubic lattice. On cooling, ordering commences at a temperature of 450° to 470°C., depending on the composition. The degree of ordering progressively increases at lower temperatures until it becomes virtually complete at about 100°C. The electrical resistivity of the alloy illustrates the changes clearly (Fig. I). This type of reaction has been a favored subject for study by physicists. An excellent summary of the theory is to be found in a paper by F. C. Nix and W. Shock1ey.l All published data on electrical conductivity, specific heat and other properties agree in indicating that the ordering reaction in beta brass takes place so rapidly that it cannot be prevented or even retarded by quenching&apos; With most ordered alloys, cold-working induces disorder and

Jan 1, 1943

By Cyril Stanley Smith

BeTa brass (consisting of approximately equal atomic proportions of copper and zinc) exists as a random solid solution at high temperatures, hut at low temperature< an ordered structure is stable, with the copper and zinc atoms occupying alternate sites on the body-centered-cubic lattice. On cooling, ordering commences at a temperature of 450° to 470°C., depending on the composition. The degree of ordering progressively increases at lower temperatures until it becomes virtually complete at about 100°C. The electrical resistivity of the alloy illustrates the changes clearly (Fig. I). This type of reaction has been a favored subject for study by physicists. An excellent summary of the theory is to be found in a paper by F. C. Nix and W. Shock1ey.l All published data on electrical conductivity, specific heat and other properties agree in indicating that the ordering reaction in beta brass takes place so rapidly that it cannot be prevented or even retarded by quenching&apos; With most ordered alloys, cold-working induces disorder and

Jan 1, 1943

By W. N. Best

Crude oil attracted attention because of its excellence as a fuel for openhearth furnaoes; for making crucible steel and brass; for melting copper, lead, tin, zinc, nickel, silver, malleable iron, gray iron; and for the production of steam in all sizes and types of boilers. For heating furnaces, mold-drying ovens, core ovens, ore roasters, calciners, hotair furnaces, sand drying, asphalt road work, etc., its superiority over other fuels is due to the fact that the heat is at all times under perfect control, so that a constant temperature may be attained and maintained at the will of the operator. This mcans a maximum amount and uniform quality of work. Crude oil is of two kinds, paraffine base and asphaltum base, and varies from 11 to 46 gravity BaumB. The light-gravity oil does not require heating before use; but oil of less than 20 gravity Baumé should be heated to just below its vaporizing point, in order to reduce its viscosity and to obtain the highest efficiency of combustion. Heavy California oil vaporizes at 230". F., Mexican crude oil at from 175" to 210" F., and Beaumont, Texas, oil at 142" F. Fuel oil vaporizes at 130" F. Scientific Installation Essential The burning of oil is an art based on science, and the "rule of thumb" should never be employed, especially in heating heavy crude oil. Thermometers should be used on both suction and supply pipes so that the fireman or smith will at all times know the temperature of the fuel. The indicators on such thermometers should be large enough to be readily seen by the operator, night or day. It is necessary to have an unvarying pressure of steam or air through the burner, to atomize the fuel. Also, the air used to support combustion should be delivered through a nozzle under the burner at a constant pressure. The oil pressure must not fluctuate; under no eircumstances should it vary more than 1 1b. The oil pump, which should be brass-lined, with the aid of the pulsometer and superheater, will insure a constant

Jan 1, 1916

By E. T. Turkdogan

In this theoretical paper, a transport-reaction mechanism is suggested for the enhancement of the rate of vaporization of metals, or other materials, brought about by the process of convection and condensation. Based on theoretical reasoning it is predicted that, when there is a temperature gradient surrounding the heated object, a slight increase in the rate of vaporization brought about by natural convection is enhanced further as a result of condensation of the vapor close to the surface of the object. In order to derive the effective vapor-concentration profile, consideration is given to the super saturation of the vapor necessary for the homogeneous nucleation of the condensed phase from the vapor. For the formulation of the rate equation based on this mechanism, adequate information should be available on the transport properties of gases and vapors at elevated temperatures and the method of calculating nucleation pressures of the vapor. The methods of deriving such data are discussed in the paper and a rate equation is calculated for the vaporization of iron in helium for various temperature gradients in the boundary layer. Considerations are also given to the effect of oxygen on rates of vaporization of metals under isother ma1 and nonisotherma1 conditions. THE study of the methods of enhancement or retardation of basically transport-controlled vaporization reactions is of theoretical interest with possible practical implications. There are several ways of bringing about such effects. For example, Turk-dogan, Grieveson, and Darken1 demonstrated that the rates of vaporization of metals under isothermal conditions were increased by several orders of magnitude, up to the maximum rate attainable in vacuo, by introducing some reacting gas into the inert atmosphere surrounding the metal. Such an effect is brought about by the interaction of the counter-diffusing reacting gas and metal vapor in close proximity of the metal-gas interface. Another case which is often experienced in practice is that of vaporization affected by natural convection. Although several theoretical and experimental studies of this problem have already been made, no detailed consideration has been given to the possible effects of condensation of the vapor in the boundary layer on vaporization rates, which constitutes the subject matter of this paper. BASIC CONCEPT OF ENHANCED DIFFUSION-LIMITED VAPORIZATION When a heated object, for example a metal sphere, is submerged in a fluid medium, heat is transferred from the surface of the object to its surroundings by four simultaneously occurring transfer processes: i) free-molecular conduction at the gas-solid interface over the distance equal to the mean free path of the gas, ii) conduction and convection through the fluid-dynamic boundary layer, iii) latent heat of mass transferred, and it!) radiation. The free-molecular conduction becomes pronounced only when the total pressure in the system is very low, e.g., below 1 mm Hg. Therefore, this term may be neglected for ordinary pressures. At low mass-transfer rates, due to vaporization of the object, the contribution of process iii) to the heat transfer can also be neglected. Finally, since the temperature profile is not affected by radiation, the latter need not be considered. The natural convection is brought about by gravitational body forces arising from a decrease in the

Jan 1, 1964

By H. M. Howe

It has seemed to the writer that one important, and indeed sufficient reason, for our slow progress in learning the relation between the chemical composition and the physical properties of cast-iron, has been that the problem has not been attacked properly. It would be well to select the most probable working hypothesis which we can find, and proceed to test that hypothesis by comparison with observed facts, and by making new observations specially designed for such a test. Our first step, then, is to select the most probable working hypothesis ; and to attempt this selection, to state the hypothesis and its immediate corollaries, and to take some first steps toward testing it, is the object of the present paper. Its chief purpose is to bring the hypothesis to the attention of those who are more familiar with the evidence than the writer can pretend to be, and in a better position both to present new evidence and to discuss it. The hypothesis here selected is, that composition governs properties in the case of cast-iron, in the same general way and for the same reasons as in the case of steel, mutatis mutandis. This hypothesis, which of course makes no claim to originality, certainly seems reasonable and probable; its exposition and discussion are made easy by our existing knowledge of the constitution of normal or " carbon " steel; it therefore seems worthy of consideration.

Jan 1, 1902

By John D. Gill

The purpose of this paper is to invite attention away from the obvious. direct monetary costs of oil-field overdevelopment (as distinguished from "social costs") to a consideration of the role played by the exercise of freedom to create even allegedly excessive1 plant facilities in contributing to the maintenance of equilibrium in the wholc economy and in promoting material progress. The obvious and most commonly discussed effect of overdevelopment of oil fields is illustrated by the allegation that already the excessive development of the East Texas field has cost upward of $162,000,000;2 in other words, the drilling of 12,500 wells more than the number estimated as the requirement for economical recovery of the reserve has unnecessarily raised the total cost of development that amount. Many other illustrations of so-called excessive development of oil pools could be presented. Some of them, like Cushing, Powell and Long Beach, might be drawn from the era antedating widespread discussion in the trade of such matters as optimum well spacing, reservoir energy, the conservation rate of depletion of reserves, etc. Numerous other cases can he found in the records of the current era, which began with the introduction of rationalized restriction of production. Besides East Texas, there may be mentioned Oklahoma City, Centralia and. more recently, the town-lot development of Bloomingdale, Michigan.

Jan 1, 1940

By John D. Gill

The purpose of this paper is to invite attention away from the obvious. direct monetary costs of oil-field overdevelopment (as distinguished from "social costs") to a consideration of the role played by the exercise of freedom to create even allegedly excessive1 plant facilities in contributing to the maintenance of equilibrium in the wholc economy and in promoting material progress. The obvious and most commonly discussed effect of overdevelopment of oil fields is illustrated by the allegation that already the excessive development of the East Texas field has cost upward of $162,000,000;2 in other words, the drilling of 12,500 wells more than the number estimated as the requirement for economical recovery of the reserve has unnecessarily raised the total cost of development that amount. Many other illustrations of so-called excessive development of oil pools could be presented. Some of them, like Cushing, Powell and Long Beach, might be drawn from the era antedating widespread discussion in the trade of such matters as optimum well spacing, reservoir energy, the conservation rate of depletion of reserves, etc. Numerous other cases can he found in the records of the current era, which began with the introduction of rationalized restriction of production. Besides East Texas, there may be mentioned Oklahoma City, Centralia and. more recently, the town-lot development of Bloomingdale, Michigan.

Jan 1, 1940

By A. W. Hahn

THE importance, to geologists and metallurgists, of knowing the mineralogical forms in which the silver occurs in ores has increased during the past few years, and will continue to increase as long as working hypotheses are converted into proved theories and rule of thumb methods are supplanted by scientific data. The methods used for the determination of these silver minerals have been: (1) careful study of polished ore sections with the microscope, and more recently, (2) metallurgical separation of the ground ore by flotation, tabling and panning, supplemented by microscopic examination of these separated minerals, and chemical analyses. During the course of some experimental work carried on by the testing department of the International Smelting Co. and myself, it becomes important to determine, in a general way, the distribution of the silver values in the minerals, as they exist in Tintic Standard and North Lilly siliceous oxidized lead-silver ores. These mines are in the East Tintic Mining District, State of Utah. In this work the second method was used. Differential flotation tests were run, separating the sulfide from the oxidized minerals, and the products were assayed. Various concentrates were carefully panned and the separated products assayed; special samples of ore were selected and assayed. The microscope was used only for the purpose of determining whether the individual minerals were in the so-called "free" state.

Jan 1, 1929

By Frederic Lahee

THE purpose of this paper is to demonstrate the similarity of the oil-producing structures in the Mexia1 fault zone, and to show how the apparently very irregular well logs in these fields may be used for the practical interpretation of subsurface conditions. The Mexia oil field, in Limestone County, Tex. (Fig. 1) is closely associated with a fault that trends about 30° east of north and has a displacement of between 200 and 400 ft., with downthrow on the west. Minor slips accompany this major fault, some being roughly parallel to the main break while others are transverse to it. These faults belong to the so-called Mexia fault zone, a belt of fracturing that has been traced in its characteristic features southward to near Kosse, 15 miles south of Groesbeck, in southern Limestone County, and northward at least as far as the Trinity river at the eastern border of Navarro County, and possibly as far north as Hunt and Hopkins counties.2 The Balcones fault zone, from 30 to 40 miles west of the Mexia fault zone, differs from the latter in that its principal displacement is a down-throw on the east. In this respect, it is exactly the opposite of the Mexia displacement. Between these two zones of major faulting lies a great down-dropped block, or graben, which is broken by numerous minor faults.

Jan 2, 1925

C. H. MATHEWSON, New Haven, Conn. (written discussion *).-In a recent discussion of Dr. Jeffries&apos; paper on tungsten,1 J. C. W. Humfrey,2 after taking exception to certain of the author&apos;s ideas relative to the cohesion of A and C metal, expresses the opinion that future research is likely to develop a method of preparing tungsten possessing "mechanical properties in line with those of other metals." The present paper by Dr. Jeffries begins with a determination of comparative properties of tungsten, copper, and iron, in which much dissimilarity is apparent, and ends with a coherent explanation as to why much of this dissimilarity is natural and inevitable, thereby supplying theoretical means for visualizing the changing properties of metals in general, once certain fundamental facts are known. The author&apos;s reasoning is primarily from the standpoint of the amorphous theory and his principal achievement is the development of an idea f differential cohesion according to conditions of temperature, etc., between A and C metal (which was first plainly suggested by Rosehain and Ewen, in their papers on Intercrystalline Cohesion of Metals) along with associated ideas, so as to give us a really useful working theory. I have come rather reluctantly to believe in the amorphous theory, or some theory admitting a modification of the ordinary crystalline phase so as to permit differential properties within the conglomerate, mainly because in no other way does it seem possible to account for observed changes of properties with temperature, etc. The very best illustration f the competency f the amorphous theory in this respect is seen in this and other recent papers by the author. All fractures through normal or healthy metal that have been preceded by deformation are supposed, by Dr. Jeffries, to take place either through the amorphous phase or at certain boundaries between amorphous and crystalline material; his reference to fractures, both members of which are similar in appearance and do not reveal a preexisting coarse-grained structure because of a coating of amorphous metal, indicates his preference for the former interpretation.

Jan 5, 1919

By R. Clare Coffin

The production of petroleum in the Rocky Mountain district increased from 27,104,436 bbl. in 1929 to 33,048,630 bbl. in 1930. This increase was due to the development in southeastern New Mexico; which is in reality a portion .of the West Texas province. Disregarding production in southeastern New Mexico, the Rocky Mountain district produced 25,799,027 bbl. in 1929 and 23,164,988 bbl. in 1930, a decrease of 2,634,039 bbl. for the period. The daily production in January, 1930, averaged 70,839 bbl. for the entire district and in December, 1930, the daily production was 98,995 bbl. Total production by states is given in Table 1. Three important discoveries of oil and one of gas occurred in the district during 1930 in structures not, previously known to contain oil or gas. Oil was discovered in Dry Creek structure, Carbon County, Mont.; in the Midway structure, Natrona County, near Casper, Wyo.; and in the Greasewood structure, Weld County, Colo., northwest of Fort Morgan. Gas was discovered in the Bell Rock structure in Moffat County, western Colorado. Seven deep tests in as many different fields encountered oil in lower horizons than those already exploited. All of these discoveries were in the state of Wyoming. They occurred in the Salt Creek field, Natrona

Jan 1, 1931

By H. L. Stone, A. O. Garder

A numerical method of solving the partial differential equations which describe the one-dimensional displacement of oil by gas has been presented. Possible extension of the method to treat multidimensional flow is discussed, and the limitations of this extension are indicated. Using this method, it is possible to allow for the existence of a gas cap, the presence of any number of gas-injection or oil-production wells and the evolution of dissolved gas from the oil. It is also possible to allow for variation in the cross-sectional area, elevation, porosity and permeability of the reservoir. The influence of relative permeability and the force of gravity in the direction of flow upon the displacement is considered. The influence of capillary pressure upon the flow and the effect of gravity in the direction perpendicular to flow are neglected. The physical properties 01 the fluids are considered to be Junctions of pressure only, and equilibrium between contiguous phases is assumed. The numerical calculations can be readily carried out by the use of a digital computer. Several example analyses have been performed using the IBM 704 computer, and about one-third of an hour of computing time was required per case. Reservoir behavior predicted by use of this numerical method was compared to data obtained by other methods for three cases — complete pressure maintenance, dissolved-gas drive and gas-cap drive. The independent solutions to these problems were obtained by analytical solution, laboratory experiment and field data, respectively. Agreement of the numerical solution with data from these sources was good; this agreement establishes the convergence and accuracy of the numerical method. INTRODUCTION Most petroleum reservoirs can be produced by any one of several alternative programs. When a reservoir is produced by primary methods, production economics can be influenced by controlling the number and location of wells and the flow rate of each well. An even greater influence may be achieved by augmenting the recovery of oil obtainable by primary methods. This can be accomplished by injection of fluids such as water, natural or enriched gas or a bank of light liquid hydrocarbons. Selection of the most desirable operation requires a means of predicting the reservoir behavior which will result from each of the several alternative programs. The purpose of this paper is to present a mathematical method for predicting the behavior of reservoirs produced by gas-cap drive, dissolved-gas drive or pressure maintenance by gas injection. The method described herein takes cognizance of phase changes caused by a decline or an increase (due to gas injection) in reservoir pressure, of the presence of a gas cap and of the effect of gravity on the flow of gas and oil. Relative permeability relationships are used to define the flow properties of the rock. Allowance is made for variation in cross-sectional area, elevation, permeability and porosity of the reservoir. Both the influence of capillary pressure upon the flow and pressure gradients in the gas cap are neglected. Whenever a liquid phase and a gas phase are in contact, they are assumed to be in equilibrium. The physical properties of the fluids are considered to be functions of pressure only. Therefore, if the method is to be used to predict the effects of a gas-injection program, mixtures of the injected gas and formation crude should-have the same physical properties as mixtures of formation gas and crude. The equations to be presented in this paper apply only to a one-dimensional case; therefore, they neglect the influence of gravity in the direction transverse to the flow. As is well known, this gravitational influence may lead to overriding of oil by gas. Consequently, this procedure as presented is most applicable to long, thin reservoirs for which gravity overriding is not important. On the other hand, the equations presented can be generalized to treat multidimensional flow and, hence, to consider gravity overriding, if desired. A word of caution on two points is advisable here, however. First, the authors have not demonstrated the accuracy of the numerical technique for multidimensional flow. Second, and more important, capillary pressure will often be of importance in multidimensional problems. Obviously, in such cases a generalization of the

By W. Blaschke, E. Malysa

INTRODUCTION In recent years in Poland, a problem connected with the occurrence of a considerable amount of liberated galena grains in size fractions under 1mm has arisen in the zinc-lead processing area. Operating practices have included crushing of ore particles under 0.2 mm followed by flotation. Jigs were applied to separate the concentrates from size fractions under 10 mm and to prevent the galena overgrinding. However, the fractions being too wide, the jigs have not worked effectively, in spite of the great differences in specific gravities of galena, blende and gangue minerals. Fine galena grains move into light fractions in considerable amounts and hence are overground. Therefore, the flotation becomes difficult and galena is lost in its tailings. These losses could be avoided by introducing separation in the grinding and classification circuits. The amount of 0-1 mm fraction is great; therefore, the application of concentrating tables or other kinds of jigs is impossible from an economic point of view. Taking these factors into account, the possibility of application of pinched-sluices was investigated. These are simple devices without moving parts, they have a high output for the unit areas, and their water and energy consumptions are low. In this paper, the results of zinc-lead ores beneficiation in pinched-sluices are presented.

Jan 1, 1980

By Leo Dana

INTRODUCTION THE object of this paper is to discuss the factors and conditions that affect the observed values of the melting points of refractory materials and to describe practical methods for the determination of these points. While it appeared to be necessary to discuss some of the general properties of silicates and refractories, these subjects have been entered into only in so far as they relate to the melting point and its determination. Refractory materials such as fireclays, firebricks, and minerals generally, may be considered to be composed of compounds of metallic oxides, solid solutions of the oxides, the pure oxides, or mixtures of the three classes together with small amounts of a variety of chemical compounds. The oxides of silica and alumina occur most commonly in refractory materials; in combination with. these, oxides of the alkali earth, the alkali, the iron group, and the rare earth metals are frequently found.

Jan 9, 1919