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By T. R. Scott

The acid pressure leaching of zinc-lead flotation concentrates from the McArthur River deposit, Northern Territory, Australia, has been studied in a three-stage, continuous, co-current system, using titanium reactors of 6 gal capacity. The starting pulp contained 2.7 lb solids per gal of synthetic spent electrolyte and the final liquors contained 120-125 gpl Zn. Parameters investigated included temperature (95-120°C), oxygen pressure (30-100 psi), acid addition (80-130% of theoretical), and leaching time (35-65 min per stage). Technical factors studied included mixing and pumping of feed, agitation, settling and washing and control mechanisms. The chemistry of liquor impurities, of scale formation in autoclaves and of lead jarosites in residues was studied in some detail. Results indicated that 90-93% zinc recovery could be obtained with a "low- acid" process, using 113°C and 70 psig with oxygen as the favored operating conditions. Residues contained 16-18% elemental sulphur and 15% lead, together with unreacted pyrite and gangue minerals. Pelletizing of residues was impracticable, and alternative suggestions for the recovery of lead, sulphur and silver are discussed. Preliminary estimates for plant and operating costs are given and enable some comparison to be made with conventional procedures.

Jan 1, 1973

By Ancel St. John

During a session on coal and coke at the February, 1926, meeting of the American Institute of Mining and Metallurgical Engineers, the writer called attention to the important work on the X-ray analysis of coal1,2 being carried on in England by C. Norman Kemp and his associates. This aroused so much interest that a paper on the subject was requested for the October meeting. It has seemed advisable to make this paper a preliminary survey of the present status in the application of X-ray methods to coal problems and to follow it from time to time with further articles as the art develops. A survey of this sort naturally divides itself into two parts, radio-scopic analysis of the distribution of constituents through the body of the coal, and diffraction analysis of the state of association of the elementary components. In this article the subject matter concerning radioscopic analysis has been drawn almost entirely from the writings of Kemp and his associates and the illustrations have been sptcially furnished by him. It is a pleasure to record here a great indebtedness for this courtesy and cooperation. The subject matter and illustrations concerning diffraction analysis are taken from the author's unpublished researches. Nature and Properties of X-rays Before proceeding it is well to recall the nature and some of the properties of X-rays, as well as our present conception of atomic structure According to the accepted theory atoms are composed of electrically-charged particles. A positively-charged center, called the nucleus,

Jan 1, 1927

By M. Deighton, R. N. Parkins

The metals Cd, ,Wg-, Sn, TI, Zn, and Zr reach a peak hardness after a criticfir1 deformation by rolling- and then soften with fwther rolling-, thereby exhibiting wovk softening. Optical metallography on Cd, Mg, and Zn shows that work softening is accompanied by a change in grain size occurring during deformation. The creep of zinc from -1l° to +60°C at stresses in the range of 7.9 to 17.3 kg per sq mm is given by € = e0 -t- Bt + Kt +at6. The third and second rate constcints are related by the equation a = K~ K6 and their stress and temperature dependence can be represented by the equations K = A, . exp - (u, - Bu)/kT. A model based upon the stress activated glide of sub-boundaries is proposed which qualitatively accounts for the metallog-raphic observations. Expressions, which are in reasonable quantitative agreement with the ex-pe~inzental observations, are derived for the creep of zinc. THE term "work softening" has been used previously by Polakowski1 and by Cottrell and stokes2 to describe phenomena where further strain of a deformed material leads to a decrease in flow stress. In both cases, however, the conditions were changed for the second straining. Here, the term "work softening" is intended to refer to a decrease in flow stress after continued straining in the same direction at the same temperature: work softening is the antithesis of "work hardening". Work softening of zinc was reported by chadwick3 and in discussion of that paper Jenkins4 indicated that cadmium also work softens. More recently work softening has been reported5 in two magnesium alloys, -99.5 pct Mg. Chadwick found that the hardness, 0.2 pct Proof Stress and the UTS of electrolytic zinc all increased with progressive cold reductions up to 30 pct and then progressively decreased with further rolling. Gay and Kelly6 used a back-reflection X-ray technique to study the effect of cold rolling zinc and found that although deformations greater than 2 to 5 pct reduction in thickness produced some recrystallized grains, deformations greater than 40 pct caused com-plete spontaneous recrystallization. At deformations greater than 60 pct the material was found to consist solely of recrystallized grains, -20 pm diam, the size of which decreased with increasing reduction and was much less than the initial grain size of the annealed material (-300 pm diam). Similar results were also reported for cadmium, tin, and lead.6 Gay, Hirsch, and Kelly' suggest that these experiments indicate recrys-tallization takes place when the dislocation density exceeds a certain value. However, no measurements of MATERIALS AND EXPERIMENTAL PROCEDURE The purity of the metals used in this work is indicated by the following figures: Zn (99.99); Cd (99.94); Mg (99.95); T1 (99.99). The zirconium was iodide crys tal bar with a probable purity of about 98 pct. The metals were obtained in the form of 0.25 in. thick strip or 0.425 in. diam rod by various fabrication methods and then annealed to ensure complete re-crystallization. Hardness-deformation curves were obtained at room temperature by rolling 4 in. thick strip under conditions which left a surface adequate for diamond pyramid hardness tests immediately after rolling. The hardness was taken as the niean of five impressions made using a 5 kg load and the time elapsing between rolling and making the last impression never exceeded 5 min. The zinc specimens for creep testing were from 3 by 3 by 4 in. cast slabs which were rolled to 0.10 in. thickness starting at 350°C and finishing cold. The resulting strip was cut into pieces 1 in. wide and annealed in batches. With suitable choices of annealing temperature between 100" arid 400°C five different grain sizes varying from 4.54 x 10' to 3.03 x l05 grains per sq cm (530 to 20 um diam) were obtained. Creep tests were done in compression using a sub-press, based on a design after Ford,8 in which the strip is compressed between dies 0.100 in. wide under conditions of plane strain. Since there is no lateral spread of the material, the area of contact between the dies and strip remains constant throughout the test and the application of a constant load, using the load maintaining device of a hydraulic testing machine, resulted in a constant stress. Covering the dies with strips of P.T.F.E. reduced frictional effects to a minimum. The creep strain was obtained by measuring the travel of the crosshead of the testing machine to a sensitivity of 0.1 pct reduction in thickness. The complete subpress assembly was contained in a steel box and for tests above the ambient this was filled with liquid paraffin and heated electrically. Temperatures below the ambient were obtained with a cooling mixture of acetone and solid carbon dioxide in the box. The liquids were stirred and the temperature of the specimen, which was controlled to ±0.5"C dur-ing a test, was measured by a thermocouple placed near the dies. Compression testing of cylindrical specimens was also carried out in the subpress using hardened flat discs separated from the test material by P.T.F.E. sheets which obviated barrelling of the specimens. Various initial strain rates were supplied by the hydraulic testing machine, and the deformation was measured by a clock dial gage resting on the cross-

Jan 1, 1970

By W. A. Backofen, G. Y. Chin, W. F. Hosford

The ductile fracturing process was studied in single-crystal and poly cvystalline aluminum deformed in tension over a temperature range from 295° to 4.2°K. At temperatures as low as 77°K, the fracture of "inclusion-free" material, including zone-refined aluminum, was by rupture (-100 pct RA). At 4.2 OK, fracture was brought on by adia-batic shear. Metallographic examination did not disclose any voids or slip-band microcracks, thus negating for inherently ductile metals any mechanism of void nucleation by vacancy condensation or of cracking due to dislocation pile-ups. In Izigh-purity aluminum not treated to be inclusion-free, fracture at temperatures as low as 45°K was of the double-cup type and a result of void formation. The reduction-of-area decreased as temperature was lowered, corresponding to the earlier appearance of voids. Such behavior was rationalized in terms of a larger increase, with decreasing temperature, in the .flow stress relative to the strength of the inclusion-matrix interface. Evidence for low-temperature adiabatic shear was found in discontinuous flow at 4.2"K, in the transition to a localized shear fracture at low temperatures, and in the suppression of shear fracture with an elastically hard pulling device. A simple analysis for the initiation of adiabatic shew permitted a general correlation of the various contributing factors. It has been pointed out that the duration of shear depends upon effective mass and elastic stiffness of the deformation system. IT has long been recognized that fracture* may Throughout this paper, the term "fracture" is taken to mean any process that results in the separation of a material into two (or more) parts. Thus rupture as it may be encountered in a tension test leading to 100 pct reduction-of-area is included in this category. occur in a ductile mode, and that the process can be of great practical as well as general interest. Much information about ductile fracture has also been accumulated over this period, but only recently has an understanding of mechanism begun to appear. Ludwik,' in 1926, first reported fracture in a tensile specimen starting with a central crack in the necked section. Since then, other studies have disclosed that such cracks may form by the coalescence of voids nucleated in this region where hydrostatic tension is highest.2-4 Rogers and Crussard et al.' have emphasized void formation and reori-entation along localized shear bands as a mode of crack propagation. pines6 has considered the tensile rod as a bundle of fibers joined by weak interfaces, which subsequently separate to allow individual fiber contraction. The notion of cavity growth and coalescence by purely plastic processes was discussed by Cottrell: who added that the tensile reduction-of-area ought not to be sensitive to temperature. On the other hand, it has been observed that the reduction-of-area is greatly increased if tests are carried out at high temperaturesa or under high hydrostatic pressure.' Fracturing anisotropy in wrought products lends support to the idea of void formation from preexisting flaws strongly aligned by earlier processing.''-l2 There is evidence that many voids result from the fracturing of inclusions or separation at the inclusion-matrix interface Another possibility is that voids grow out of pore volume produced in the initial solidification and never fully removed in later working. In general, a structure 3f particles, pores, and weak interfaces can be expected, at least in materials of engineering interest. Vacancy condensation has been suggested as an alternative mechanism of void formation for materials considered to be inclusion-free.13 Yet experience has shown that tensile reduction-of-area increases with purity, to the extreme of rupture as so often observed in single crystals. Adiabatic shear has an important bearing on ductile fracture. It occurs when the decrease of flow stress, as a result of local temperature rise from heat generated during straining, becomes larger than the increase due to strain and strain-rate hardening. As demonstrated by experiments on punching of plates,14 a large temperature rise may be brought about by rapid straining. Adiabatic flow as a result of the high strain rate reached in an ordinary tensile specimen just prior to separation may account for the cone formation in cup-and-cone fracture;14 evidence of such local heating has been presented.15 For geometrical reasons, however, pure sliding along the conical surfaces is unlikely, and separation under tensile forces is probably an important accompanying feature of the shear.7 In deformation processing operations, a high shear-strain rate may exist at boundaries between plas-

Jan 1, 1964

By Earl W. Palmer, Cyril Stanley Smith

A study of the precipitation-hardening of copper steels1 led the authors to investigate malleable iron containing copper, for the low-carbon ferritic matrix in malleable iron should lend itself admirably to precipitation-hardening. It was soon found that in addition to rendering malleable iron susceptible to improvement by precipitation-hardening treatments, copper has another potentially useful effect as an accelerator of graphitization. Brief mention of these effects was given in a general paper by Lorig and one of the present authors2; the present paper gives further details on the graphitization and precipitation-hardening effects only. After the completion of this work a paper by L. Lykkin3 appeared, confirming the authors' conclusions regarding graphitization. Material Used After some preliminary heats had been made in the laboratory to determine the effect of copper, several castings from commercial air-furnace heats were obtained, and data from these alone are given here. Part of the metal was poured directly and part was treated in the ladle with the desired amount of copper before pouring. Green-sand molds were used, each holding two tensile test pieces of the form adopted by the Malleable Iron Research Institute, or two bars for graphitization studies, 5/8 in, in diameter and 9 in. long, fed through two enlarged sections equidistant from the middle and ends of the bars. Risers of suitable size insured sound castings. Tensile tests were made on the castings after commercial mallealleizing and after special heat treatments to be described. The analyses of the white irons are given in Table 1.

Jan 1, 1935

By Cyril Stanley Smith, Earl W. Palmer

A study of the precipitation-hardening of copper steels1 led the authors to investigate malleable iron containing copper, for the low-carbon ferritic matrix in malleable iron should lend itself admirably to precipitation-hardening. It was soon found that in addition to rendering malleable iron susceptible to improvement by precipitation-hardening treatments, copper has another potentially useful effect as an accelerator of graphitization. Brief mention of these effects was given in a general paper by Lorig and one of the present authors2; the present paper gives further details on the graphitization and precipitation-hardening effects only. After the completion of this work a paper by L. Lykkin3 appeared, confirming the authors' conclusions regarding graphitization. Material Used After some preliminary heats had been made in the laboratory to determine the effect of copper, several castings from commercial air-furnace heats were obtained, and data from these alone are given here. Part of the metal was poured directly and part was treated in the ladle with the desired amount of copper before pouring. Green-sand molds were used, each holding two tensile test pieces of the form adopted by the Malleable Iron Research Institute, or two bars for graphitization studies, 5/8 in, in diameter and 9 in. long, fed through two enlarged sections equidistant from the middle and ends of the bars. Risers of suitable size insured sound castings. Tensile tests were made on the castings after commercial mallealleizing and after special heat treatments to be described. The analyses of the white irons are given in Table 1.

Jan 1, 1935

By C. S. Harloff, Frank R. Corwin

THE Nichols Copper Co., associated with the Phelps Dodge Corp. and the Calumet & Arizona Mining Co., has constructed at El Paso, Tex., and is now operating a copper refinery with a yearly capacity of 100,000 tons of anodes. Transportation facilities were perhaps the most important of the considerations that led to the selection of this site. The rapid industrial development of the Middle and Far West has increased the consumption of copper there. The advantage of local refining as against shipping the copper to the Atlantic sea- board is apparent. Copper refined in the Southwest is equally competitive for export shipment, either from the Gulf or the Pacific Coast ports. The tonnage of copper produced in the Southwest not only justifies the construction of this plant, but may warrant considerable expansion in years to come.

Jan 1, 1930

By C. W. Hoffman, W. R. Hinken

Probability sizing, a fairly recent development in the field of particle separation, is now under investigation to determine its value to the mining industry. The method employed is probability sizing through a vibrating network of decreasing screen openings. While probability sizing is not new, the possibility of using it for coarse, highly abrasive ores at high tonnage rates has only recently appeared to merit practical consideration. The advantages of probability sizing vs. conventional screening methods are: (1) reduced space requirements for a high capacity unit, (2) fewer moving parts, (3) more versatile product sizing selection, (4) reduced maintenance requirements, and (5) lower power consumption. Screening is a necessary part of virtually every crushing circuit. At some stage in the process, particle separation becomes a controlling factor in the operation. The basic type of screen in use today is the vibrating unit, which usually employs a mechanical vibrator of one type or another to obtain sizing and material transportation across the screen surface. The vibrating screen has its limitations and inherent problems. Operators must live with: (1) high maintenance — worn rods, screen cloth, spacers, cross members, chutes, etc., (2) low capacity in relation to floor space requirements, (3) extreme noise levels, (4) high power consumption, and (5) structural problems in the screens and supporting steelwork. All plant operators have become tolerant of these drawbacks through the years, and little innovation has been developed in screening. The vibrating screens in use today incorporate improved metals, more efficient power sources, better lubricants, and increased manufacturing skill, but the basic machine itself remains unchanged. Screening is a relatively small part of most plants' operating expenditures and gets relatively little attention from research and development. The HiProb sizer is a new approach to the problem of particle separation on a high tonnage basis. Developed by Dr. Fredrik Mogensen (president of Fred-rik Mogensen, A. B. of Djursholn, Sweden), this unit has found its primary acceptance in the sizing of wet or dry materials in the fine ranges. Climax has been working cooperatively with Mine and Smelter Supply Company, the United States licensee, on the adaptation of the sizer to obtain consistent recovery at a high tonnage rate on a — 3/8-in. separation. This was a new application for the sizer and opened up a whole new field of problems. Dr. Mogensen's machine utilizes the control of normal probability of falling particles and is designed to eliminate some of the undesirable features of vibrating screens mentioned earlier. The machine is light, compact, consumes less power than conventional screens and has a low noise level. PRINCIPLES Probability sizing is a process designed to allow solid particles to segregate with a high ratio of the materials reporting into their respective size fractions with a minimum amount of misplaced particles. Sizing is defined in this paper as segregation of dry solid particles into fractions of comparable sizes. Probability is usually estimated as the ratio of the number of ways an event might occur vs. the total number of allowable ways. The probability process described depends upon the fact that particles falling through a network will segregate across the sizing surface even though all openings are larger than the particles. The degree of segregation is dependent upon the particle size and the trajectory applied by the sizing network to each falling particle. Specifically, the process utilizes a maze made up of screen cloth to control the path of a particle in free fall as illustrated in Fig. 1. The usefulness of this probability sizing process is dependent upon the degree of efficiency of an effective maze. Primarily, a maze must be extremely flexible to meet the multi-faceted nature of solid particles and, at the same time, the degree of control must be reproducible so that a desired separation is predictable. Dr. Fredrik Mogensen has formulated a maze that is not only flexible and easily controlled, but, mote importantly, easily adaptable to a working machine.

Jan 1, 1970

By W. R. Hibbard, Ming-Kao Yen

Various rationalizations of preferred orientations in cold worked polycrystalline metals have been based on the operation of at least two three2 five, an indefinite number, and all,6 slip systems of the type occurring in single crystals. Pickus and Mathewson3 suggested that the cold rolling texture in face-centered cubic metals could be rationalized on the basis of two or more operating slip directions symmetrically disposed about the direction of flow in such a manner that the resolved shear stress factor is equal for all operating slip systems and lattice rotations cancel each other. The importance of the direction of flow, the necessity for the operation of slip systems capable of producing the required changes in external dimensions, the maintenance of a common surface between adjacent grains and a symmetrical arrangement of the operating slip systems in order to produce an end orientation which is stable under additional deformation lead to the following rationalization of textures based on the type of slip systems operative in single crystals. The rationalization is intended to explain why certain orientations are suitable for deformational flow without a change in orientation and thus are stable end orientations or ideal texture orientations. It does not attempt to explain how the grains of a randomly oriented polycrystalline aggregate will reach this orientation. The rationalization is based on the following four postulates: 1. The ideal textures for polycrystalline aggregates are the result of reorientations of individual crystals toward the same stable end orientation at which no further reorientation will occur even during additional deformation. Since, in simple slip, the relative orientations of the stress axis and the active slip system determine the change in orientation during slip, it is considered that the orientation of the stress axis with respect to the ideal texture determines what slip systems must be active to retain the stable end orientation. Therefore the stable end orientation should be a symmetrical one around the stress axis with respect to the active slip systems such that lattice rotations resulting from slip will cancel each other and prevent a resultant change in orientation. (Rotational symmetry only—not translation, inversion, nor others—is considered here.) Thus a metal under a pure stress should develop a texture consisting of one or more of the crystallographically symmetrical directions, <100>, <110> or <111> for cubic metals or <0001>, <1010> or <1120> for hexagonal close-packed metals, parallel to the stress axis. 2. Since the active slip direction is the direction of glide during simple slip and thus the direction of maximum shear movement, in the ideal texture the active slip

Jan 1, 1949

By Ming-Kao Yen, W. R. Hibbard

Various rationalizations of preferred orientations in cold worked polycrystalline metals have been based on the operation of at least two three2 five, an indefinite number, and all,6 slip systems of the type occurring in single crystals. Pickus and Mathewson3 suggested that the cold rolling texture in face-centered cubic metals could be rationalized on the basis of two or more operating slip directions symmetrically disposed about the direction of flow in such a manner that the resolved shear stress factor is equal for all operating slip systems and lattice rotations cancel each other. The importance of the direction of flow, the necessity for the operation of slip systems capable of producing the required changes in external dimensions, the maintenance of a common surface between adjacent grains and a symmetrical arrangement of the operating slip systems in order to produce an end orientation which is stable under additional deformation lead to the following rationalization of textures based on the type of slip systems operative in single crystals. The rationalization is intended to explain why certain orientations are suitable for deformational flow without a change in orientation and thus are stable end orientations or ideal texture orientations. It does not attempt to explain how the grains of a randomly oriented polycrystalline aggregate will reach this orientation. The rationalization is based on the following four postulates: 1. The ideal textures for polycrystalline aggregates are the result of reorientations of individual crystals toward the same stable end orientation at which no further reorientation will occur even during additional deformation. Since, in simple slip, the relative orientations of the stress axis and the active slip system determine the change in orientation during slip, it is considered that the orientation of the stress axis with respect to the ideal texture determines what slip systems must be active to retain the stable end orientation. Therefore the stable end orientation should be a symmetrical one around the stress axis with respect to the active slip systems such that lattice rotations resulting from slip will cancel each other and prevent a resultant change in orientation. (Rotational symmetry only—not translation, inversion, nor others—is considered here.) Thus a metal under a pure stress should develop a texture consisting of one or more of the crystallographically symmetrical directions, <100>, <110> or <111> for cubic metals or <0001>, <1010> or <1120> for hexagonal close-packed metals, parallel to the stress axis. 2. Since the active slip direction is the direction of glide during simple slip and thus the direction of maximum shear movement, in the ideal texture the active slip

Jan 1, 1949

By E. S. Leaver

The authors of the paper above mentioned have sent the following statement to correct erroneous com-ments and implications in their article with the re-quest that it be published: "In the above mentioned article the reference to Bendelari jigs is used in the generic sense as applying to the mechanically driven diaphragm jigs. No attempt was made to dif-ferentiate between the various machines as installed on different dredges. The Natomas Company use a jig of their own manufacture. The Yuba Company installed the Placer jig as manufactured by the Pan American Engineer-ing Company. "The Pan American Engineering Company also manufactures the Crangle jig under their own name. This is a diaphragm jig in which the pulsations are produced by intermittent flow of water through the patent Crangle Valve and it has no driving mechanism."

Jan 1, 1937

By Thomas Watson

INTRODUCTION THE users of barite in the United States derive their supply partly from the domestic production and partly from the imports from foreign countries. According to the Mineral Resource division of the U. S. Geological Survey, the domestic production of barite in 1913 was 45,298 short tons, valued at $156,275, or $3.45 a ton, and the imports of crude barite were 35,840 short tons, valued at $61,409, or $1.71 a ton. These figures clearly show a decided advantage in cost of the foreign over the domestic barite to users in the United States. The difference in cost is the only advantage to the consumer of foreign barite, for there are large reserves of the mineral in the United States of good grade. The production of many of the operating mines is capable of decided increase, and it is believed that the operating mines together with the large reserves of undeveloped deposits of barite are entirely adequate to meet the demands of the users in the United States. Deposits of barite are known in California, Idaho, Nevada, and Alaska, but most of them are undeveloped because there is, apparently, no market for the .material in that region. The domestic production is derived from Missouri and the Appalachian States, the greater part being obtained from Missouri. Following the outbreak of war in Europe many users of foreign barite in the United States have been forced to seek their supplies at home. It seems opportune at this time, therefore, that a general review be given of the barite industry in the Appalachian States, one of the two areas from which the domestic supply of the mineral is derived, and that attention be directed to the undeveloped deposits in the region. Briefly, then, this paper reviews the barite industry in the Appalachian States, and describes the occurrence, preparation, and uses of the mineral.

Jan 2, 1915

By H. LIVINGSTONE LMAN

A GOOD DEAL of information concerning flotation has come out during the patent litigation of recent years, and the legal situation has cleared considerably, to the satisfaction of Minerals Separation, Limited. Hence, Mr. H. Livingstone Sulman, one of the originators of the successful process of that company, felt at liberty to explain, on Thursday, Nov. 20, his experience and his views in a "Contribution to the Study of Flotation," before the Institution of Mining and Metallurgy. He did not give technical details. He dealt with the physical problems, so simple, as he remarked, that he had wanted 96 pages to express his views. He presented much data, partly new and based on observations of his own, bearing upon the very complex flotation phenomena in an instructive wav and made frequent references to the valuable researches especially of Prof. Edwin Edser and Mr. Emil Hatschek.

Jan 1, 1920

By Vince Poxleitner, John Delaney

Introduction In the mining industry, comminution typically begins in the mine with a blast of explosive to break rock so that it can be handled by the avail- able equipment. Though the breaking of the rock is essential for material handling in the mine and plant, this is not the only reason for ore reduction in the mineral industry. Comminution is primarily required to liberate minerals from ore so that they can be concentrated into valuable products or to prepare minerals, such as talc, for market as mined. The size of the equipment used for comminution ranges from small to massive. Regardless of equipment size, the power required to reduce the rock is a major expense. Years ago, mineral deposits could be mined more selectively and required less grinding to produce saleable products. However, as richer deposits were depleted, it has become necessary to mine low-grade deposits, with the valuables dispersed throughout the rock. Comminution equipment evolved in physical size and capacities to meet the new mine and process requirements. A modern, modestly sized mining operation, with a capacity of 25.000 TPD may use crushers two stories high weighing over a million pounds, SAG mills 36 feet in diameter driven by dual motors putting out 10.000 horse- power, and ball mills over 16 feet in diameter . Because of the increasing size and weight of modern equipment, the builder is faced with the problems of erecting massive foundations and field assembling equipment on these foundations. As equipment costs and plant construction costs increase, builders are finding that owners are asking for more detailed progress and cost data. Comminution construction projects are generally classified as grass roots plants or expansions or modifications to existing plants. It is estimated that 60-702 of the jobs involve existing plants. Today &apos; s costs for construction of small, new comminution plants can reach tens of millions of dollars; larger plants can cost hundreds of millions of dollars. Modifications, on the other hand, usually run from a few thousand to several million dollars. Though many problems are common to the construction of both new plants

Jan 1, 1982

By T. Egleston

FOR a great part of the progress of the world we are indebted to the works of engineers. It is to them that we owe our means of rapid transportation, our canals, our railroads, our bridges, many of our automatic machines, and most of those appliances which, by facili tating or decreasing the amount of human labor to be expended and by utilizing the great forces of nature, have made the present progress of the world possible. Their education is a matter of momentous interest to the whole civilized world. I have, therefore, thought that some discussion of the theory upon which their education should be based would be of interest to this body, and have ventured a few reflections and suggestions upon the subject. The word education, in its original signification, meant the draw ing out of a man what there was in him. In our common schools the practical work of education consists in putting into the brain a larger number of facts than can be retained, which are consequently more or less understood and digested. It ordinarily consists simply of teaching a round of abstractions or facts which when not assim ilated are not only useless to the individual, but generate careless habits of thought and make more or less untruthful, unfaithful or unsuccessful men. In most of our schools a procrustean system is adopted; all are made to advance upon one general plan, the quick being kept back and the slow dragged on at a rate too great for their power of comprehension. Until within a very few years it has been a theory in common school education that the brain alone should be developed, and that little or no attention need be paid to the train-

Jan 1, 1888

By Simon D. Strauss

Production and consumption of nonferrous metals in the United States during 1950 were at peak levels for the postwar period, as is shown in Tables I, II, and III. The trend of production was upward through most of the year. At the year end, with the possible exception of the Tri-State zinc-lead district, the large mining operations in the country were running at capacity. The absence of serious labor interruptions during the year was an important contributing factor in the increased out-put of metals, since in each of the previous postwar years there had been a number of major strikes which affected production adversely.

Jan 2, 1951

By T. D. McKinley

Theory, operational characteristics, and indicated precision and accuracy of analytical methods based on vacuum extraction, equilibrium pressure, and combustion approaches are reviewed. At the present time vacuum extraction at 1400°C and the equilibrium pressure method are recommended for determination of hydrogen in titanium and titanium-rich alloys. UNTIL a few years ago the role of hydrogen in titanium was an unknown factor with regard to its effect on the physical and mechanical properties of the metal. However, following the work of Jaffee and othersa-" it is now generally acknowledged that hydrogen has a degrading effect on titanium and its alloys. The chief manifestations are a decrease in impact strength in -systems and delayed cracking in a-ß systems. Since hydrogen does have a de- grading effect on titanium it is essential to control it within tolerable limits. It then follows that procedures for quantitative estimation of hydrogen are a primary requirement for the industry. For greatest benefit these methods should be simple, rapid, and precise. In addition to having these virtues, methods must be easy to duplicate in both equipment and technique to gain widespread use. After inherent accuracy has been established, the, required precision to make a method acceptable is dependent largely on the nature of the work at hand. Ability to obtain a representative sample has a pro-

Jan 1, 1959

By W. W. Duecker

SULPHUR is a peculiar combination of a nuisance and a useful element. Most of the nonferrous metallic ores contain large amounts of it in the form of sulphides, which the metallurgist has wasted up the chimney, since the sulphur dioxide formed is generally too dilute to make recovery economical and practical. Iron ore does not contain much of the unwanted sulphur; in pig iron and coke it is most unwelcome. Gold metallurgists can get along nicely without sulphides in their cyanide plants and yet they find matte-a sulphur compound -an excellent collector for gold and silver in base-metal smelting. Also, sulphur appears in the non-metallics as in barite, gypsum, Glauber&apos;s salt, and celestite, all to useful purpose.

Jan 1, 1938

By G. L. Oldright, F. W. Schroeder

Very great changes were made in the dimensions of the smelting hearths of the furnaces in the period from about 1800 to 1906, the length increasing from about 11 to 116 ft., and the width from 8 to 19 ft. During this time the tonnage smelted increased from about 9 to 250 tons per 24 hr., and the tons of charge smelted per ton of coal increased from 0.77 to 4.3. Dr. Mathewson3 noted no great difference in the "fuel ratio" (i. e., the amount of charge smelted per ton of coal) as the furnace at Anaconda was increased in length by stages from 85 to 116 ft. (The percentage of copper in the slag, however, was lowered from 0.42 to 0.36 per cent. The other components of the slag were not given.) Lump coal fired on grates was the fuel used during this period. The practice in operating the furnaces over such a length of time naturally varied considerably, and there were differences in composition and nature of the charge, yet it may he considered that the improvements made were due largely to increases in the size of the furnace used. Doubtless some credit should be given to improvements in operating technique, like changes in the methods of firing the lump coal. However, the greater part of the advance was probably due to factors influencing the

Jan 1, 1928

By Paul H. Price

The history of the salt industry in West Virginia dates back nearly two hundred years; however, the history of salt as an important raw material for the chemical industry is much more recent. The earliest record of West Virginia salt was in 1753, when a raiding party of Shawnee Indians attacked frontier settlements in Virginia taking captive a number of the pioneers. One of these, who later escaped and returned to her friends, described how the Indians camped at a salt spring on the banks of the Kanawha River and evaporated the water to obtain a supply of salt to take back to Ohio with them. Settlement of the Kanawha Valley began in 1774, that same year the Battle of Point Pleasant ended the Indian&apos;s power in the Ohio Valley; and settlement of the Kanawha Valley progressed rapidly with a consequent increase in the importance of the Kanawha Licks as a source of salt. In those days the evaporation of the brine was a family matter for which the family wash-kettle was commandeered.

Jan 1, 1949