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By MILNQR ROBERTS

THE Nicola Valley coal-field is small, but it seems likely to become important because of its commanding position in a rich region that is developing rapidly. Bituminous coking coal in workable quantity has not been found at any other point between the Crow's Nest Pass region, about 400 miles to the east, and Vancouver island, 250 miles westward. The Canadian Pacific railway reached the Nicola valley two years ago; two other lines, the Canadian Northern and the Great Northern, are building towards the valley. The vast region between the Rocky mountains and the Pacific coast, extending northward for several hundred miles from the international boundary, which has been the scene of extensive mining- and smelting-operations for many years, is filling up with settlers, who are attracted by the wealth of minerals and timber, the rich soil of the valleys, and the fine climate. The Nicola river, flowing westward through the valley of that name in the Yale district, discharges into the Thompson river, which is the eastern branch of the Fraser. The transcontinental line of the Canadian Pacific railway crosses the mouth of the Nicola river at Spence's bridge, 178 miles from Vancouver. From Spence's bridge the Nicola branch line ascends the valley for 40 miles to Merritt, the coal-center, and continues 7 miles farther to the town of Nicola. Thus the haul from the mines at an elevation of 2,000 ft, to saltwater is 218 miles down river grades. The Nicola branch will be continued about 150 miles farther eastward to Penticton, where it will connect with an extension of the line through the rich Kootenay and Boundary districts. The Canadian government has granted a subsidy of $6,000 per mile, to which the pro-

Jan 1, 1910

By William S. Hannan, H. Rush Spedden

FLOTATION may be defined as a process whereby mineral particles are concentrated by selective adhesion to air-liquid interfaces. The process involves attachment of desired mineral particles to air bubbles, and removal of the mineralized air bubbles from the surface of the pulp as a mineral concentrate. PROBLEM Although great strides have been made in understanding the principles of flotation, one part of the process which has not been adequately explained is the mechanism by which selected mineral particles become attached to air bubbles. A glance at the froth of an operating flotation cell demonstrates adequately that use of proper reagents and conditions will result in such attachments; but how such attachment takes place is not definitely known. A better knowledge of this factor might lead to improved flotation practice either through altered machine design or the application of scientific innovations. Direct observation of the behavior of mineral particles and bubbles in an operating cell does not appear promising because of the complexity of the system. For this reason, conclusions concerning the problem must be deduced from theoretical considerations or from observation of simplified systems designed to reproduce conditions thought to exist in an operating cell. PRESENT THEORIES Two mechanisms have been recognized as fundamental in particle-bubble attachment: gas precipitation and direct encounter. It is a simple matter to demonstrate in the laboratory that attachment can be brought about by either mechanism. As to the relative importance of the two in a particular flotation system, however, there is a divergence of views. Taggart1 states, Under exceptional circumstances sufficient force and time to effect attachment may conjoin in an ore pulp undergoing agitation, and a preformed bubble adhere to a collector-coated mineral particle, but the occurrence is rare. . . . Pulp-body froth flotation effects selection in the body of a conditioned pulp by causing gas bubbles to precipitate from solution in the liquid phase preferentially at the surfaces of collector-coated particles, and to cling to these particles. Gaudin2 states that, within the pulp body of an agitation machine, attachment of mineral particles to air bubbles occurs as a consequence of contact between the two. This theory has been supported by theoretical reasoning and much circumstantial evidence. Perhaps the most interesting bit of evidence in favor of this theory is the difficulty in the flotation of fines. If attach-

Jan 1, 1947

By John Fulton

The Connellsville coal-field is a separate strip of the upper coal measures, flanking the Chestnut Ridge along its western side. It extends from a point a few miles south of Uniontown, in Fayette County, following a northeasterly course parallel to the trend of Chestnut Ridge, through Fayette and Westmoreland counties, with its terminal prongs resting 011 the southern portion of Indiana County, north of the town of Blairsville. This belt of coking coal will average about three miles in width and over sixty miles in length, affording nearly, if not quite, two hundred square miles of this large coal-bed.

Jan 1, 1885

By L. K. Welch, C.W. Macgregor

The past 20 years has seen a revolutionary change in the testing of materials at elevated temperatures. This has largely been brought about by the practical importance of the creep problem in the design of equipment for operation at high temperatures. The short-time tension test carried out at elevated temperatures has consequently assumed in many cases only a secondary role compared with the longtime creep test. In many problems, however, a knowledge of the short-time high-temperature properties of a metal is essential. To mention a few cases in which this is so, we might include all hot-forming operations such as rolling, forging, etc., the welding problem if residual stresses are to be computed, the development of new alloys for high-temperature service where, in the initial stages, time does not permit of long duration creep tests, and others. Usually a knowledge of the short-time properties is desired, if only to serve as a background against which to compare creep behavior. In conducting short-time high-temperature tests, it has been almost the universal practice to determine stresses based on the original area and strains referred to the original gauge length which is usually chosen as 2 in. It has been pointed out1,2 that one of the reasons that the true significance of certain tensile properties is not understood, which perhaps curtails their usefulness, especially when the material is applied under conditions differing considerably from the test conditions, is that true physical stresses and strains are not determined. It is essential to have a knowledge of true stresses and strains in order to correlate the values present in the tension test with those existing, for example, in hot metal-forming operations and in the general problem of the yielding and failure of metals under combined stress conditions. Stress and strain values based on the original dimensions of the test piece do not exist physically except in the early stages of the test. Since at the present time there is very little information in the literature on true stress-strain relations in the short-time high-temperature tension test it is proposed in the following pages to describe a

Jan 1, 1943

By L. K. Welch, C. W. MacGregor

The past 20 years has seen a revolutionary change in the testing of materials at elevated temperatures. This has largely been brought about by the practical importance of the creep problem in the design of equipment for operation at high temperatures. The short-time tension test carried out at elevated temperatures has consequently assumed in many cases only a secondary role compared with the longtime creep test. In many problems, however, a knowledge of the short-time high-temperature properties of a metal is essential. To mention a few cases in which this is so, we might include all hot-forming operations such as rolling, forging, etc., the welding problem if residual stresses are to be computed, the development of new alloys for high-temperature service where, in the initial stages, time does not permit of long duration creep tests, and others. Usually a knowledge of the short-time properties is desired, if only to serve as a background against which to compare creep behavior. In conducting short-time high-temperature tests, it has been almost the universal practice to determine stresses based on the original area and strains referred to the original gauge length which is usually chosen as 2 in. It has been pointed out1,2 that one of the reasons that the true significance of certain tensile properties is not understood, which perhaps curtails their usefulness, especially when the material is applied under conditions differing considerably from the test conditions, is that true physical stresses and strains are not determined. It is essential to have a knowledge of true stresses and strains in order to correlate the values present in the tension test with those existing, for example, in hot metal-forming operations and in the general problem of the yielding and failure of metals under combined stress conditions. Stress and strain values based on the original dimensions of the test piece do not exist physically except in the early stages of the test. Since at the present time there is very little information in the literature on true stress-strain relations in the short-time high-temperature tension test it is proposed in the following pages to describe a

Jan 1, 1943

By Raymond E. Funderburk

Today, there are four alternatives available for disposal of highly toxic, non-radioactive hazardous waste: deep well injection, chemical processing, landfill and incineration. However, based upon research conducted by the author, a fifth alternative now exists. Disposal in salt. Salt, because of its chemical characteristics, is an ideal medium for retention of inorganic hazardous waste. Except for a few elemental compounds such as lithium and potassium, there is no reaction with sodium chloride. In the family of inorganic wastes, there are basically seven suites of waste that may be mixed together without any chemical reaction. The process developed by the author would be to take a suite of waste, either dewater or add moisture, add a solidification agent to the mix and slurry pipeline the mass into a cavern. Residence time before hardening can be adjusted, but the nominal time until full solidification is 48 hours. Once solidified, the mass will reach compressive strengths exceeding 3000 psi. The slurry can be introduced into an evacuated cavern pumped free of brine, or it can be placed beneath the brine and the waste will force the brine to the surface. The latter technique requires a high degree of engineering control to prevent contamination of the brine leaving the cavern-thus creating more hazardous waste and additional problems. The Environmental Protection Agency endorses the concept both at the research level and within EPA Headquarters. The technology will soon be utilized in a salt formation in Texas.

Jan 1, 1985

By F. Milton Lewis, Roshan B. Bhappu, James L. Coburn

Part one of this article, published in the September 1976 issue of MINING ENGINEERING, described procedures for analytically evaluating the physical and chemical properties of an ore; it also described various types of equipment that are available to the minerals engineer for designing required comminution operations. Part Two of this article illustrates the practical application of these principles to the design of a sound comminution system for a known set of ore characteristics. This exercise is aimed at giving the young engineer a review of the methods and procedures that are available for designing comminution systems. To illustrate these methods, a large-tonnage porphyry copper ore body with the following characteristics is selected:

Jan 11, 1976

By Stanley D. Michaelson, Ben. H. Slothower

The depletion of most high-grade ore reserves coupled with growing demands for metals and fuels has made it necessary to bring into production increasingly lower grade deposits. Improvements in technology have made lower grade ores economically recoverable in spite of major increases in labor and material costs and the initial investments required to open new mines and build their metallurgical and service plants. To remain competitive, managements of mining companies must keep abreast of and exploit these often complex technical developments. The proper application of these improvements in technology requires extensive and detailed study. In addition, managements of mining and other industries are becoming more deeply involved in public affairs and the myriad of other nontechnical problems common to all industries. These involvements, plus the demands of evaluating technological developments as well as the necessary work related to the routine administration of operations, have required mining managements to delegate additional study and review functions to staff services. To help overcome the problems involved in adopting the best technologies, managements have generally expanded their engineering and research staff services. Integrated, base-metal-producing companies, having open pits, concentrators, smelters, and refineries, are generally more research and engineering oriented than are most smaller mining companies and quarries. However, mining methods for even the simplest open pits and quarries are improving rapidly, and installations of these improvements are essential to combat increasing costs. Because of this, the managements of smaller operations may also require enhanced engineering staff services to realize the potential benefits.

Jan 1, 1968

By Richard Moldenke

One of the gravest problems of the iron foundry today is the accumulation of sulfur in commercial scrap and its effect on the castings made therewith. The ordinary jobbing castings today show a sulfur content of 0.18 per cent;, and occasionally as high as 0.22 per cent. The product of the foundry during the war is undoubtedly to blame for this rapid increase and conditions will become worse as the millions of tons of gray-iron castings of the war period return to the foundry in the form of commercial scrap. In the ordinary cupola remelting of pig and scrap, at least 0.02 per cent. sulfur is taken up; often double that amount. The high cost and difficulty of obtaining pig iron during the war period compelled the use of considerable scrap in the mixtures; frequently charges containing 90 per cent. of bought scrap were melted. Naturally the sulfur content of the castings increased. Until the advent of the basic-hearth electric furnace, the only method of holding the sulfur within reasonable limits was to use high percentages of pig in the foundry mixtures. Pig iron seldom contains over 0.05 per cent. sulfur, if well made. With pig iron forming 60 per cent. of the charge and the gates, runners, rejections, and bought scrap the other 40 per cent., the sulfur content of the castings can easily be held down to 0.10 per cent. Pig iron, however, costs more than scrap even when melting loss differences are considered, hence as small a percentage as possible will be used. The recent advance in knowledge of rational melting and the consequent reduction in losses directly due to oxidation of the metal and cold iron, has permitted the acceptance of castings with a much higher sulfur content than formerly. The steel industry also is seeking to determine how high sulfur may go with safety. In the iron foundry, however, there is the danger of a low cupola bed or an unduly retarded air-furnace heat, with the consequent raising of the freezing point of the metal and segregation effects resulting from high sulfur with insufficient manganese. The iron foundryman must, therefore, have a means of correcting his

Jan 1, 1922

By Richard Moldenke

One of the gravest problems of the iron foundry today is the accumulation of sulfur in commercial scrap and its effect on the castings made therewith. The ordinary jobbing castings today show a sulfur content of 0.18 per cent;, and occasionally as high as 0.22 per cent. The product of the foundry during the war is undoubtedly to blame for this rapid increase and conditions will become worse as the millions of tons of gray-iron castings of the war period return to the foundry in the form of commercial scrap. In the ordinary cupola remelting of pig and scrap, at least 0.02 per cent. sulfur is taken up; often double that amount. The high cost and difficulty of obtaining pig iron during the war period compelled the use of considerable scrap in the mixtures; frequently charges containing 90 per cent. of bought scrap were melted. Naturally the sulfur content of the castings increased. Until the advent of the basic-hearth electric furnace, the only method of holding the sulfur within reasonable limits was to use high percentages of pig in the foundry mixtures. Pig iron seldom contains over 0.05 per cent. sulfur, if well made. With pig iron forming 60 per cent. of the charge and the gates, runners, rejections, and bought scrap the other 40 per cent., the sulfur content of the castings can easily be held down to 0.10 per cent. Pig iron, however, costs more than scrap even when melting loss differences are considered, hence as small a percentage as possible will be used. The recent advance in knowledge of rational melting and the consequent reduction in losses directly due to oxidation of the metal and cold iron, has permitted the acceptance of castings with a much higher sulfur content than formerly. The steel industry also is seeking to determine how high sulfur may go with safety. In the iron foundry, however, there is the danger of a low cupola bed or an unduly retarded air-furnace heat, with the consequent raising of the freezing point of the metal and segregation effects resulting from high sulfur with insufficient manganese. The iron foundryman must, therefore, have a means of correcting his

Jan 1, 1922

By W. A. Longacre

IN the geophysical exploration program of the Cleveland-Cliffs Iron Co. on the Marquette Range of Northern Michigan, the vertical intensity magnetometer has been used to obtain magnetic anomaly maps of large areas. A network of magnetic base stations has been established and the relative vertical intensity at each station measured carefully with respect to a prime base. In the search for the relatively nonmagnetic soft red hematite ore, the magnetic exploration is indirect, involving the study of dikes, faults, contacts, and other structural features. It was found that the magnetometer, adjusted to a scale value of approximately 40 ? per scale division, was satisfactory for this type of exploration, although many magnetic anomalies were encountered that required the use of auxiliary magnets.

Jan 1, 1952

By Walter O. Snelling

In the course of some experiments more than five years ago, made for a totally different purpose than the investigation of the oil used, I placed a small quantity of a transparent yellow lubricating oil in a bomb-like vessel and heated it to a relatively high temperature. At the end of the experiment I removed the oil from the vessel and was amazed to find that instead of bearing any resemblance to the oil which I had put in, it now had the appearance of ordinary crude oil. The green color by reflected light and the rich red-brown by transmitted light were so unmistakable as to at once lead to further investigation. I subjected the material to fractional distillation, and the surprise which I experienced at the appearance of the oil, changed to amazement when I found that it yielded, on distillation, 15 per cent. of gasoline and 30 per cent. of burning oil, and that its constitution resembled crude oil quite as much as did its appearance. Furthermore, the gasoline and kerosene distillates which it yielded were of a clear water-white color, entirely without treatment with acid or alkali, and were entirely free from the odor familiar in "cracked" petroleum distillates. The result of this experiment was quite too remarkable to be credited without further confirmation, and I at once filled the vessel with some of the same oil that I had used before, and again heated to about the same temperature that I had previously used, and for the same period of time. Upon opening the vessel and removing the contents I found, not the material resembling crude oil that I had obtained before, but apparently only the same oil that I had put in, somewhat darkened in color, but nevertheless far different in appearance from the material obtained in the previous experiment. Evidently some condition existed in the first experiment that had not existed in the second test, and here began a series of tests in which I sought by the change of one variable after another to arrive at the identical conditions which must have existed in the first experiment. Only the fact that the bottle of heavy oil used in the first test was still in its place,

Jan 1, 1915

By Dave H. Barnett, Brij M. Moudgil

The flotation technique as employed by Florida phosphate producing companies for the beneficiation of fine phosphate particles has been standardized over the years. Lower recoveries of coarse phosphate rock by froth flotation technique, however, led to the development of new methods based on skin flotation of phosphate agglomerates. Recent developments of floating coarse rock in large flotation machines have not yet convinced the rock producers of their higher separation efficiency. It is interesting to note that the selection of a particular machine is still based on equipment preference by an individual company as well as proven performance of a particular machine for upgrading a specific material. Various techniques which have been developed to beneficiate the coarse phosphate rock have been discussed. Performance of the individual techniques is presented.

Jan 1, 1980

By R. S. MACPHERRAN

TRENDS in the manufacture and use of cast iron are decidedly toward specialization, alloy iron, and increased strength. Old handbooks list only one kind of cast iron, with a tensile strength of 15,000 lb. Recent A.S.T.M. specifications show that from 50,000 to 60,000 lb. per sq. in. can now regularly he guaranteed. The use of alloy iron, heat-treated iron, and even nitrided cast iron, is rapidly growing and all kinds are improving in quality. Iron for operation at high temperature and corrosion-resisting irons have also been developed. Only a few years ago cast iron was "cast iron," but now there are almost as many kinds of cast iron as there are foundries making it

Jan 1, 1936

By C. Laird, C. E. Feltner

IN previous workif2 we have shown that the steady state cyclic stress response of pure copper tested in the low cycle fatigue range was determined only by the plastic strain amplitude and the test temperature. hus, copper, at any given temperature, has a unique cyclic stress-strain curve independent of prior history. Cu-7.5 wt pct Al, however, showed a stress response for a given plastic strain amplitude and temperature which depended sensitively on prior history. From this work we predicted that all wavy slip mode materials, typified by copper, would have a unique cyclic stress-strain curve; whereas all planar slip mode materials, typified by Cu-7.5 pct Al, would not. This prediction has now been tested for a number of materials of widely varying crystal structure and slip character. Wavy slip mode materials studied include: Fe. Al, Cd, disordered FeCo-V, and Cu-3 pct Co (quenched and aged). Planar slip mode materials investigated include: Fe-3 pct Si, ordered FeCo-V, disordered Ni3Mn, ordered Ni3Mn, and Zn. The treatment and properties of these materials are listed in Table I. Cyclic stress-strain curves were determined by controlled plastic strain tests (see Ref. 1 for details) at room temperature for all materials in both the initially annealed and cold worked conditions. The results obtained for iron and Fe-3 pct Si are typical of wavy and planar slip mode materials, respectively. The cyclic stress-strain curves for these materials are shown in Fig. 1 and it can be seen that iron has a unique cyclic stress strain curve while Fe-3 pct Si does not. Aluminum, Cu-3 pct Co, and disordered FeCo-V showed a behavior like that for iron, while Ni3Mn in both the disordered and ordered condition behaved in the same manner as Fe-3 pct Si. These results therefore support the general conclusion drawn in Refs. 1 and 2 that. for wavy slip mode materials, a cyclic mechanical equation of slate it =t.(hcp, i. T) is approximated in which the satura-

Jan 1, 1970

By J. L. W. Birkinbine

This paper is a discussion of a part of the mineral wealth of the States of Oaxaca and Paebla, Mexico. It does not refer to the precious metals, sonie mines of which, in these States, are said to have been worked before the advent of the Spanish conquistadores in the sixteenth century, as my purpose is to invite attention to the exploration of deposits of coal and iron-ores in the Mixteca region. The prominence given to coal is warranted by the great effect of the scarcity of fuel upon the industrial development of Mexico. Under the progressive administration of President Porfirio Diaz, the Republic has made wonderful advances in the past three decades; and this progress would have been greater but for the limitations imposed by expensive fuel. In the spring of 1906 I was detailed by the Birkinbine Engineering Offices, of Philadelphia, to accompany A. B. Adams, of New York, in a reconnoissance of reported deposits of iron-ores in the State of Oaxaca. The result of this expedition was the formation, in 1907, of the Oaxaca Iron & Coal Co., of which Mr. Adams became, and has remained, President and General Manager, and I have spent the past three years as Chief Engineer of this company in Mexico, principally in western Oaxaca, where field-headquarters were established. GEOGRAPHY AND POPULATION. Although the geographical and topographical features of the Republic of Mexico are well known, few realize that the majority of its population is domiciled in the States which immediately surround the capital city of Mexico, including the Federal District, Mexico, Tlaxcala, Morelos, Puebla,

Jan 1, 1911

By P. K. Currie, J. V. Walters

Solution mining of magnesium salts (Carnallite and Bischofite) is taking place near Veendam, in the northeast Netherlands. The magnesium salts are used for the production of magnesia sinter, used as a base material for the manufacture of refractory bricks for furnaces. This paper gives, first, an introduction to the operational procedure followed in Veendam, with the emphasis on some of the unique aspects, and then discusses rock-mechanical aspects of the cavity behaviour. The creep behaviour of magnesium salts is described, and Finite Element calculations on cavity stability and potential surface subsidence are discussed.

Jan 1, 1985

By C. E. Turner, J. R. Elenbaas, R. D. Grimm, J. A. Vary, D. L. Katz

A technique is presented by which well samples and core plugs of dolomite formations are classified by microscopic examination into seven different porosity grades. Quantitative values of porosity and permeability are determined for each grade by a statistical correlation of the core plug test data with the porosity grading system. These quantitative values are applied directly to the grades exhibited in the well samples for the purpose of estimating the reservoir void space for wells that were not cored. The procedure is described for estimating the gas reserves per unit area lor the South Hugoton gas field. but a reserve estimate for the field is not given. INTRODUCTION The miscroscopic examination of well sample; and the graphic recording of their lithologic qualities and other distinguishing characteristics of various geologic formations drilled is both a science and an art of long standing and wide application. Usually the primary objective of a geologist who "sits on the well" and examines the samples are: to identify the formation being drilled, determine the total depth, casing point. and completion interval. In most cases the porosity is described. if done at all, in general terms. such as: trace, scattered, fine, poor, fair, medium. good, excellent, or in some other relative terms. In fields where various geologists have examined samples and recorded observations on many wells considerable variations in lithologic terms and porosity descriptions occur unless there is primary effort to establish uniformity of logging observations and standards of recording observable porosity. When an estimate of the pore volume of a reservoir is made a geologic concept of the processes that control the magnitudes of porosity and permeability is developed by microscopic examination of well samples. The characeristics and appearances are then mentally related to rather general quantitative units of porosity based on physical core data from the same reservoir or on such data or experience in other reservoirs that have similar qualities. The reliability of such estimates depends largely on the variations of the lithology of the formations, the geometric properties of its void system. the extent of comparisons of sample appearances with porosity data, as well as the uniform recording of all relevant characteristics. This statement is particularly significant for dolo-mitized limestone formations of substantial thicknesses and heterogeneity such as the Permian Dolomites of the Hugoton gas field. Jn this field, as well as in most of the Permian Dolomite fields, the producing formations are of relatively great thicknesses in which the porosity and permeability of the reservoir varies substantially in all directions, depending on the crystalline structure. degree and kind of impurities, kind of fossils anti cementation thereof, degree of dissolution. and fracturing. The variations of the lithologic texture of the dolomites and post deposition alterations have resulted in porosities and permeabilities of such magnitudes that only a part of the gross thickness can be counted as "pay." At the time of this study insufficient gas production had been experienced to apply the pressure decline production method in the South Hugoton Field and the electric logs are not definitive enough. The problem of estimating gas reserves in the south part of the Hugoton Field is primarily one of determining the pay thickness and porosity from well samples and core data. The area studied embraced all that part of the field lying south of an east-west line through Guvmon, Okla., anti containing approximately 1.000,000 acres. This paper describes a technique of correlation of physical core data with well samples so that quantitative values of pay thickness, porosity. Permeability, and connate water may be assigned to well samples that are representative of a given interval, and thereby permitting the estimation of gas reserves lor a given unit area. The procedure was developed by a uniform microscopic qualitative porosity grading of the dolo. mite core plugs.. and relating these grades to the respective physical core data on a statistical basis The well sample-were also graded in a Similar manner in order that the quantitative values established lor the core plugs could be applied to the well Sample for wells that were not cored. GRADING OF DOLOMITE A group of experienced geologists was given the assignment of examining the samples on all wells in South Hugoton in order that they could log their observations in a uniform and standardized manner and grade the observed porosity so that it could be related quantitatively to the core data. The group initiated the study 011 chips from cores which bad been tested for porosity and permeability. This study continued until all of the geologists developed a common knowledge of lithologic terms and of the characteristic appearances of the samples and their relations to measured porosity. The characteristic appearances of the dolomite samples under twelve-power magnification as related to their qualitative porosities afforded a classification of the dolomite into :even grades of porosity, ranging from dolomite of no-visible porosity under twelve-power magnification to dolomite of excellent porosity. The assigned grade for a specific 10-ft interval is a weighted average of all visible grades of porosity exhibited by the cuttings representing that interval. The porosity characteristics were recorded by a color graph adjacent to the lithology column in conjunction with a numerical system for further definition of relative porosity as shown in Fig. 1. The three vertical lines to the right of the lithology column each represent 33 1/3 per cent. which lines were used to record the percentage of the samples, for any particular interval. that showed porosity under the microscope. The colors were used to denote actual pore size. i.e., orange. blue and I-ed for pore diameter of one-fourth or less. one-fourth to one-Ilalf. and greater than one-half millimeter, respectively. The area colored 1)). one or more colors represents the percentages of the samples exhibiting pores of the respective size or sizes. The numerals from one to six inclusive shown on the log in

Jan 1, 1952

By S. Usui, I. Matsuoka, H. Sasaki, J. Shimoiizaka

Depression of galena by sulfite or chromate ion in xanthate flotation was investigated by means of adsorption measurements, electron diffraction and flotation tests. Flotation of galena was depressed by sulfite ion only when galena had been oxidized; no depression took place with unoxidized clean galena. A similar behavior was found when chromate ion was used as a depressant, with the exception that the chromate ion depressed unoxidized clean galena around neutral pH. Depression was attained with galena on which xanthate still remained in appreciable amounts, indicating that the depression is not due to a decrease in xanthate adsorption. The galena surface produced sparingly soluble films under conditions in which depression of galena took place. These films were identified by electron diffraction as lead sulfite and lead chromate on oxidized galena and as chromic oxide on unoxidized clean galena. These observations in conjunction with contact angle measurements, indicate that the depressing action of sulfite or chromate ion arises primarily from film deposition resulting from the reaction between depressants and the galena surface. The thickness of the film was analyzed by means of electrochemical polarization.

Jan 1, 1976

By B. G. Zambre, G. A. Parks, J. N. Roco

Automatic controls have long been a fact of technological life. Some understanding of control systems is rapidly becoming essential to the competence of mineral engineers. Students in undergraduate mineral engineering curricula, however, should not be expected to develop proficiency in the design and interpretation of control systems. They should be provided the opportunity to absorb some of the fundamental concepts and cant of such highly specialized peripheral fields as automatic controls. The present paper describes the components of a simple, flexible and relatively inexpensive control system designed primarily for the use of students in independent study projects. The control system is based on a continuous on-stream optical analyzer analogous to commercially available systems using X-Ray fluorescence analysis. The components can be easily adapted to control other separators and separations. As described here, they have been arranged to control the magnetic separation of a magnetite bearing specular hematite from quartz to produce a quartz product of fixed hematite content using a minimum of power. The control system consists of the magnetic separator* with a vibrating feeder, † a sampler, an optical scanner, a differential amplifier, a millivolt recorder ‡ and a motor driven, metered variable DC power supply for the separator electromagnet. An optional magnet current recorder is useful. The system as arranged for closed loop control is illustrated in Fig. 1. The elements of the loop are identified in automatic control jargon in Table I. The same components can be easily adapted for use in other control modes.§.1 * A Carpco Induced Roll High Intensity Magnetic Separator (Carpco Manufacturing, Inc., Jacksonville, Fla.); modified for external magnet power supply. A Jeffrey-Traylor Vibrating Feeder Type 1B (Jeffrey Manufacturing Co., Columbus, 0.). A Beckman Laboratory Potentiometric Recorder (Beckman Instruments, Inc., 619-A) fitted with adjustable limit switches for external circuit control (Beckman Instruments, Inc.. 71980). Terminology is taken from ref. 1. CLOSED LOOP OPERATION The separation is monitored through the optical reflectivity of the tailings stream which is proportional to the hematite content, THA. The difference, A, between the measured analysis (actually a proportional voltage) and a reference analysis (also a proportional voltage) is continuously recorded. The separation is controlled through changes in the electromagnet current, I, supplied from a motor driven variable source. The two primary variables, ? and I, are linked through adjustable limit switches on the

Jan 1, 1965