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A Feasibility Study to determine the future of ZC Mines was completed in mid 1987. Early in this study, which lasted two years, it was identified that significant reductions in treatment costs would result if the Zinc Corporation Concentrator was closed. All of the production from the existing two mines, The Zinc Corporation Limited (ZC) and New Broken Hill Consolidated Limited (NBHC), would then be treated in the concentrator at NBHC.After a partial upgrade of the NBHC concentrator, the ZC concentrator was finally closed and all of the equipment disposed of. This closure highlighted the need to concentrate all ore haulage in one shaft to further reduce operating costs and remove the cost of surface transport of ZC production to the improved NBHC concentrator. This paper outlines the changes that were made to improve the haulage system for ZC Mines. After a number of options were investigated, it was finally decided that the upgrade of the existing NBHC haulage shaft was the best option even though some production would be lost while the upgrade was in progress.

Jan 1, 1988

Answers to the questions "which rocks contain diamonds?" and "which indicator minerals should diamond explorers look for?" are no longer so easily obtained, now that diamonds are known to occur in lamproites and various types of lamprophyres, as well as their traditional source of kimberlites. One way of isolating those factors (host-rock"geochemistry, geographical or tectonic location, xenolith minerals, etc.) which are most critical in determining the diamond potential of a given pipe, is a detailed and critical re-examination of the huge volumes of accumulated data on kimberlites, lamproites and related rocks. A large analytical database to this end has been set up on an Apple Macintosh II microcomputer using the quasi-relational database management system 4th Dimension. Currently, it contains data for up to 90 major and trace elements, isotopic ratios and contained mineral compositions for some 4,000 rock specimens from all over the world. Many experiences in setting up this database are probably relevant to other geologists setting up their own systems: they include determining the relationships between data items; the advantages of codes over free text in representing categorical variables such as rock types; the need for rigorous error trapping and data validation; and the problem of missing data values and ambiguities thereof. The working system is now being used in a rigorous statistical assessment of the criteria which distinguish diamondiferous from non-diamondiferous rocks.

Jan 1, 1989

By McMahon DW, Schapper MA

Hard rock underground mining has been wedded to the drill-blast method of breaking rock. Current practice and technology have focused on greater efficiencies in the blasting and handling of ore, on the basis that thelower costs that come with larger scale operations compensate for the waste dilution associated with the bulk methods. However, it is suggested that new technology is available or is on the horizon that could completely change the shape of hard rock mining in the 21st century. Hard-rock continuous-mining machines, possibly assisted by high pressure water jets, coupled with automated sorting and materials handling systems, could re-orient the miner's focus to winning metal rather than mining tonnes of ore. More continuous mining processes could accelerate the penetration by high technology in the hard rock underground mine, with the potential of greater manpower productivities and lower costs per tonne of metal produced. This new technology will be important in maintaining a competitive supply of metals, given the falling headgrades of the orebodies remaining for development and the increasing market threat from manufactured substitutes.

Jan 1, 1985

The efficient design of carbon-in-pulp (C.I.P.) plants involves the integration of both process engineering and design engineering.Many recently constructed plants have not recognised the above interrelationship, and as such have incurred higher capital and operating costs than were in reality necessary. This has been compounded in some cases by slavishly following the design of plants where process conditions are different for the ore characteristics in question, thus perpetuating design errors that finally become industry "accepted practice".In the paper that is to be presented the unit operations of crushing, grinding, classification, leaching, adsorption, desorption and electrowinning in C.I.P. plants will be discussed with reference to the integration of process and design engineering.

Jan 1, 1986

By U. F. Kocks

The flow stress in some latent slip systems of aluminum and silver crystals after various deformations in single slip was investigated by transverse compression and supplemented by experiments on overshoot of the compression axis and the stability of corner orientations. Work hardening was found to be remarkably isotropic, the ratio of the flow stress in the latent system to that in the primary system being between 1.0 and 1.3. The strain-rate dependence was not significantly larger in the latent system. This low anisotropy suggests that specific dislocation interactions are not the direct cause of work hardening. Either the obstacles are essentially impenetrable so that only their distance enters, or a fairly random distribution of dislocations of all systems is. in fact. formed during single slip. The latter seems to he excluded by the observations on the strain-mte dependence and on the amount of secondary strain. The amount of seconzdary strains occurring in single slip was determined by shape-change mensurements and by a new method connected with the latent-hardening experiments. It is definitely less than 1/300 times the strain in the primary svstem. WORK hardening is due to dislocation interactions; this is a hypothesis, and possibly the only one, on which all present work-harden ing theories agree. About a dozen specific interactions have been considered, and it is unlikely that any essential one has been missed. Different work-hardening theories differ to a large extent in the specific interactions which are deemed most important. The presence or absence of any particular interaction, and its degree, depend on the geometrical relationships between the two dislocations interacting. Let us enumerate some examples. Two dislocations may react, with a varying reaction energy, to form a third dislocation, and this reaction product may be sessile or glissile. Two dislocations may intersect and a jog may be formed on both, on one of them, or on neither; this jog may be sessile17Z or glissile and it may, if moved nonconservatively, lead to the production of vacancies or interstitials. Finally, a dislocation may bypass another one and thus interact only with its stress field. All these interactions depend on the specific relation between the Burgers vectors and line directions of the two dislocations. Any dislocation generated during plastic deformation of fcc crystals belongs to one of twelve slip systems. Taking any one dislocation, its relationship to each of the other eleven can fall, by symmetry, into one of only five classes. These relationships are enumerated in Fig. 1 and Table I. Each slip system is represented in the stereo-graphic projection by two triangles, namely those in one of which the specimen axis would have to lie if the specimen were to deform in single slip on this slip system in a given sense, in a tension test. Let us represent the primary slip system by the shaded triangles. The other slip systems are classified only with respect to their relationship to this primary system. The code letters (initials of established names* in German) are explained in Table I. Three specific interactions are also listed in cases where they may be strong: the product of a reaction, the formation of jogs in either system, and the elastic bypass stress. The last column relates to the types of experiments reported in this paper and summarizes their results. To decide experimentally between the relative importance of the various interactions one would like to produce a group of dislocations in one slip system and then measure the stress necessary to force another group of dislocations of a specific second system through them. Hopefully, one can produce the first set of dislocations by plastically deforming the specimen in single slip. Then one can try to achieve single slip in a specific, previously latent system and measure its flow stress. If it is different from the virgin flow stress, there has been "latent hardening". Some types of latent-hardening experiments will be discussed in the next section. The strain-rate and temperature dependence of the flow stress is an indication of the importance of dislocation intersections. By extending an investigation of this dependence to the latent systems, one can determine how much more important forest contributions are here. seeger3 has used the as-

Jan 1, 1964

By Laurence D. Burke

The electrocatalytic behaviour of gold in aqueous media is surprisingly complex and a novel view of gold electrode surfaces is proposed to explain the observed electrochemical responses. The metal surface is considered as a chemically (or redox) modified electrode, with equilibrated, low energy, surface gold atoms functioning as a relatively inert support and low coverage, high energy, protruding gold atoms (or minute clusters of same) functioning as electrocatalytic redox mediators. The protruding atoms are viewed as surface active sites and the complex electrocatalytic behaviour is attributed to the basic instability of the mediators, the diversity (and poor control) of same, and the acid/base (or hydrolysis) behaviour of the oxidized states of the mediators. It is assumed that major advances in the application of gold in the heterogeneous catalysis of gas phase reactions will be accompanied by similar advances in the use of gold in the electrocatalysis area; however, this will require considerable work of both a practical and theoretical nature.

Oct 1, 2003

By W. J. Mcgaughey, R. G. McCreary, S. C. Maxwell, R. P. Young

"Seismic tomography is a process for obtaining images or maps of seismic velocity or other seismic properties of a rock mass. Seismic velocity images reveal variation in elastic moduli which, in tum, are related to several properties required in the geological or geomechanical assessment of a rock mass. Seismic velocity is sensitive to lithology, discontinuities, and in situ stress. Spatial or temporal variation of these properties may be indirectly assessed. Tomographic measurements are sensitive to volumes of ground, rather than determinations at points, or along lines or surfaces, as in conventional geological or geomechanical measurements or mappings.Tomography surveys are complementary to conventional measurements as they have the capability to interrogate a substantially larger volume of ground. They are thus useful in discerning trends or patterns in regions between or surrounding conventional ""point"" measurements of lithology, rock quality, stress, or other parameters of interest. Seismic velocity images give broad indications of trends in velocity; their spatial resolution of ground properties is typically on the order of five to ten per cent of the nominal survey dimension.Research in seismic tomography has been carried out for several years, and the capabilities and limitations of the technique in mining environments are beginning to be understood. This report reviews the present capabilities of seismic tomography surveys in mining, emphasizing rock mechanics applications. Six case studies are used as examples to demonstrate the capabilities of the method in assessing lithological variation, density and orientation of discontinuities, and the effects of stress."

Jan 1, 1994

By G. R. Webber, P. J. Whittaker

"A multielement (Au, Cu, Pb, Zn, Ni, c-, Ag, As, Hg, Co, and S) geochemical rock sampling survey was carried out in 1977 in the Munro Township area of Ontario to assess the application of rock geochemistry for gold exploration in the region. Detailed sampling with analysis for gold and arsenic was done in 1986 in the immediate vicinity of the Croesus Mine.Samples of quartz veins and rock formations were taken in regional traverses and in more detail near old showings, prospect pits, and trenches. Quartz, graywacke, carbonate rock, and rhyolite contain the highest concentrations of gold for samples taken away from the old workings. Ultramafic rocks and gabbro have uniformly low gold. Basalt samples have slightly higher geometric means, but individual samples contain high gold concentrations. Multielement highs are mostly in mineralized quartz samples. Gold distribution is independent of other elements in most other rock types. Samples near old showings possess elevated concentrations of gold indicating that prospecting for individual mineral deposits by bedrock sampling is feasible. Concentrations of gold greater than 100 ppb are mostly within 30 m of old workings. Those samples which contain greater than 1000 ppb Au were obtained from quartz veins, basalt, graywacke, and rhyolite.High concentrations of gold were not notably concentrated near the Contact Fault although some anomalous samples came from near and on both sides of the fault. Arsenic concentrations are elevated near the Contact Fault. Detailed sampling near the Croesus Mine suggests that gold was introduced with faulting, alteration and quartz veining. Gold and arsenic have been added to the wallrock in the vicinity of the main veins."

Jan 1, 1989

By R. A. Harrington

THE structure of anodic films formed on aluminum and other metals under varied conditions is not well known despite the wide use of such films both as protective coatings and as the dielectric medium in elec-trolytic condensers. The present work was undertaken as a survey of the possibilities of electron diffraction in the investigation of anodic films, especially in comparing the properties of anodic films formed under dif-ferent sets of conditions and subjected to various subsequent treatments. In addition, an effort has been made to compare surface films formed on aluminum by anodic treatment with surface films formed by heating, immersion in chemicals, etc, The electron diffraction method in many cases has been successfully applied to the study of thin surface films. Its principal advantage is that it can be used without removing the films from the base material upon which they have been formed. The low penetrating power of electrons, in the "reflection" diffraction method which has been used in this work, prevents the appearance of diffraction patterns from substances at depths greater than about 100 Angstrom units (10-6 cm.). Different investigations of the structure of anodic films have shown widely varying results, depending on the methods used in preparing the films. Apparently under some conditions these films are crystalline and under other conditions they are amorphous, and it has been difficult to say which type of structure will be found in any particular case. Schmid and Wassermann's' X-ray diffraction patterns of eloxal? films show two broad, diffuse bands, which these investigators attribute to finely divided cubic y-Al2O3-§ Burgers, Claassen, and Zernicke3 obtained sharp X-ray

Jan 1, 1940

By R. Blickensderfer

Test equipment that simulated frictional impacts between coal-cutter bits and mineral inclusions at a coal face during operation of a continuous coal mining machine was used by the Bureau of Mines in the laboratory to study the incendivity of impacts between various rocks, metals, and hard-metal alloys in an explosive mixture of air-7 pct natural gas. Quartzitic sandstone was found to be the most incendive of several rocks tested. Limestone concretions from a coal seam, known locally as "sulfur balls," sparked furiously but were not incendive. Among the metals tested, the type of steel used in commercial coal-cutter tools was the most incendive material tested. A l7-4PH stainless steel was less incendive and appears to be the most promising high-strength steel alloy, reasonably economical, for use in coal-cutter bits. Some hard-metal alloys, primarily titanium and zirconium diboride composites, were also evaluated as possible replacements for the conventional cobalt-bonded tungsten carbide used in the tip of coal-cutter bits. The metal-bonded diborides were generally less inc endive but more brittle than the conventional tungsten carbide. Carbonitride coatings on tool bits were also tested but found to have no advantage. The source of ignition during frictional impact between metal and rock was studied. Immediately after impact, a yellow flash was observed and a smear of metal near its melting point occurred on the rock. This hotspot on the rock, rather than the yellow flash or sparks or metal fragments, was observed to be the cause of the ignition.

Jan 1, 1974

By D. R. Parrish, V. J. Berry

Reverse combustion is one thermal method of recovering hydrocarbons from porous undergrortnd formations containing oil or tar. In applying this method, air is introduced via an injection well and the mixture of air and hydrocarbons is ignited in the production well. A combustion zone then recedes toward the injection well, counter-current to the air flow. If the combustion-zorie temperature is sufficiently high, the oil or tar irz place is distilled arid cracked. The hydrocnrhon flows as a vapor to the production well and subsequently is condensed at the surface. Maximum temperature and velocity of morcment arc the two dependent variubles defining the progress of the combustion zone. A theoretical analysis has been made of heat flow in the reverse-comhustion process as.srtrning linear flow in a homogeneous system. The differentirll equatious, which include the oxygen-hydrocar-hon rctrction rate, have been solved numerically. Rescllts indicate that the maximum temperature reached and he cornbustion-zone relocity both increase with an incrense in air-injection rote. Heat loss to surroundings has little effect on the maximum comhustion-zone ten?perature achieved, but it is reflected in a reduced com-bustion-zorzc, velocity. It is also predicted that an increase in the oxygen-hydrocarbon reaction rate results in a reduction in the maximum temperature reached. The calculated results are in agreement with results from reverse-combustion experinments using samples of a tar sand. INTRODUCTION Reverse combustion is one thermal method of recovering hydrocarbons from porous underground forma-tions containing oil or tar.' In applying this method, air is introduced into the underground formation via an in-jection well. In one or more adjacent production wells, the mixture of air and hydrocarbons is ignited at the sand face. The combustion zone thus formed recedes toward the injection well, counter-current to the air flow (Fig. 1). Under certain conditions, the rate of recession of the combustion zone is sufficiently rapid that only a small fraction of the hydrocarbon at any point in the formation is consumed by combustion. If the combustion-zone temperature is sufficiently high, the uncon-sumed oil or tar in place may be partially distilled or cracked. This material then can flow as a vapor with the gaseous combustion products to the production well and subsequently be condensed at the surface. Under other conditions, the combustion-zone temperature may be so low that little, if any, of the hydrocarbon is vaporized. Nevertheless, the viscosity of the hydrocarbon may be reduced enough so that other recovery methods subsequently can be applied to produce oil at attractive rates. The maximum temperature achieved in the combustion zone and the velocity of movement are the two dependent variables defining the progress of the combustion zone. Presumably. knowledge of these factors will permit estimates to be made of oil recovery efficiency, oil and gas producticn rates and average amount of injection air required per barrel of oil recovered. The maximum temperature and combustion-zone vclocity are, in turn, expected to be dependent upon air flow rate, heat losses to surrounding formations, physical properties of the rock and the hydrocarbon. the extent to which the porous formation is saturated with the hydrocarbon, the rate of oxidation of the hydrocarbon and the amount of heat released. It is desirable that the relative importance of each of these factors be understood so that the results of laboratory tests of oil recovery by reverse combustion can be properly interpreted in terms of expected field performance. It is particularly desirable to assess the importance of heat lcsses because these are difficult to control or eliminate

By H. S. Price, R. L. Reed, J. E. Warren

The behavior of the reverse-combustion process in a linear adiabatic system is theoretically investigated by means of an idealized physical model. T his model is described by a pair of non-linear equations involving heat and mass transfer which are coupled by a concentration-dependent reaction-rate function of the Ar-rhenius type. The differential equations governing the quasi steady-state temperature and concentration distributions are approximately solved by using either physical or mathematical simplifications. It is shown that the reverse -combustion process can be mechanistically described by simple physical models whose behavior equations can be solved formally. It is further demonstrated that the derived reverse-combustion equations can be solved numerically within the error limits for the experimental data. The theoretically predicted peak temperature-flux-velocity relationship exhibits reasonable agreement with experimental data obtained from Athabasca tar sand. The principal contribution of this work lies in its usefulness as a starting point for developing a more comprehensive theory. A description of the vaporization-coking process must be obtained; then, the theory must be extended to three dimensions to include geometrical effects and heat losses. INTRODUCTION In another paper,'" he physical processes visualized as occurring during reverse combustion have been described. In this paper, the extent to which an elementary theory can account for experimental observations is determined. Theoretical results that can be used to estimate some of the behavior characteristics of importance to this process are also presented. Since it is not possible to include all the features of the combustion mechanism of which we are currently aware, the mathematical formulation refers to the highly idealized system developed herein. This simplified physical model is based on the simultaneous transfer of mass and heat accompanied by a chemical reaction: it is described mathematically by a pair of coupled, nonlinear differential equations. Similar sets of equations have been studied extensively in the field of flame propagation; an excellent review of these investigations has been published by Evans.1 FORMULATION OF THE PROBLEM It will be recalled that the experiments are performed with a thin-walled cylindrical tube that is uniformly packed with sand and oil. The system is maintained substantially adiabatic by means of heat supplied externally in such a way that the radial temperature gradient in any plane normal to the axis of the tube approaches zero. Initially, the tube is at ambient temperature, except at one end where it is rapidly heated to a predetermined temperature. When the prescribed temperature is achieved, air is caused to flow into the cold end of the tube. As the oxygen in the air stream contacts the hot oil, a localized exothermic reaction takes place. The generated heat is conducted and convected away from the reaction zone so that definite temperature and concentration profiles are rapidly established and move uniformly in a direction opposite to that of the air flow (Fig. 1). As a consequence of this mode of oxidation, all of the oxygen in the air is consumed; then, the remaining nitrogen and the gaseous combustion products sweep out all vaporized hydrocarbons and leave an immobile hydrocarbon-coke on the sand.

By John McMorran

An open pit mine design system should have the characteristics of being flexible, versatile, and simple. All of these characteristics are necessary for producing a dynamic mine design. In other words, a design that can be improved, updated, and implemented. Flexibility is an important characteristic due to changing times. For example, the effects of a changing economy, increased knowledge of the mineral deposit, or improvements in mining technology can result in a considerable, if not a complete change in the long range mining plans. Since the short range mining plans are based on the long range mining plans, they will-also be effected. Also, it is very important to validate the information used in the design or the design itself. This means the system should have the flexibility of being able, not only to detect, but to correct errors. Versatility is another important characteristic of a mine design system due to the wide range of situations that may appear. First, a design system must be able to handle both long and short term planning. This is necessary because of the variability in the definition of a time range. Second, a design system must be able to handle different types of deposits. Special emphasis must be placed on this issue, because many deposits, if not the majority, do not fit predefined categories such as bedded, massive, or roll-front, etc . . . Furthermore, the true test of the versatility of a design system is not only the ability to create an ultimate design but also to schedule sequences for this design. Thus, the versatility of being capable to design with a variety of time ranges, variety of deposit types, and scheduling are all important characteristics of the design system.

Jan 1, 1982

By Eugene McAuliffe

The mining press, as well as certain federal and state bulletins, refer from time to time to the relative hazards that attach to loading bituminous coal by hand when compared with the so-called "mechanical loading" process. Much of the coal coming under the head of hand-loaded coal is won in part by the use of machinery; the coal-cutting machine is in general use, the electric power drill employed to a lesser extent. Therefore it may be said that the principal difference in the process employed, mechanical loading versus hand loading, lies in the fact that some type of loading machine is employed in the mechanical loading process to lift the coal from the face of the room, place or entry, after it is mined, placing it in the pit cars for transport to the tipple. It is a common practice to compute accident records on the basis of tons mined per fatal and per nonfatal accident, disregarding the fact that it is possible to produce by the aid of coal-loading machines the same daily, monthly and annual tonnage with a much smaller force than is required where the coal is all shoveled by hand. Inasmuch as the men who are released by the substitution of machinery for hand labor must find employment elsewhere, suffering some measure of hazard in their new occupation, we are of the opinion that the true relative hazard that attaches to the processes of mechanical loading and hand loading can be determined only by using as the basis of comparison "man shifts worked" or "hours of exposure" experienced per accident. The Union Pacific Coal-Co., beginning with the year 1929, undertook to maintain a true record of man shifts worked per compensable accident, giving equal weight to fatal and nonfatal accidents. Accidents lacking sufficient severity to come under the compensable terms of the Workmen's Compensation Act were not included in the compilation, the Act providing that "no compensation, except the expense of medical attention, shall be allowed for the first seven (7) days of disability, unless the incapacity runs beyond the period of twenty-one (21) days, in which case the compensation shall run from the time of the injury." With the further thought that all accidents suffered by employees engaged in any service, in or about the place where the loading process

Jan 1, 1931

By Anderson K

In 1991, the first horizontal raise drill hole in Australia was successfully completed by Australian Raise Drilling Pty Ltd (ARD) at the Perseverance nickel mine of Western Mining Corporation's (WMC's) Leinster Nickel Operations in Western Australia. At that time, WMC were experiencing considerable difficulties in developing the horizontal drill drives through the orebody using conventional drill and blast techniques. Following the success of the initial hole, a further two holes were drilled as part of the evaluation program. The technique has proved so successful that it has been accepted by WMC for on-going development of drill drives at Perseverance.This paper describes the program. It relates how the project evolved, the modifications that were required to the equipment used, the performance experienced during the program and the future of the method in this and other applications.

Jan 1, 1993

By J. J. Kollé

A compressed-water hydraulic pulse generator (HPG) for nonexplosive blasting of rock and concrete is described. Energy is stored in the HPG by compressing water to ultrahigh pressure. A large, fast-opening valve discharges the compressed water, resulting in a high-energy impulse. The HPG can be used for small-scale bench blasting by discharging the water through a nozzle that is closely fitted into a borehole. A bench blasting system requires an HPG, a drill and an indexing mechanism to allow insertion of the HPG nozzle into a drilled borehole. Systems with discharge energies ranging from 40 to 250 kJ have been used to excavate hard rock, including andesite, granite and quartzite. The largest system can excavate 15 t/h (16.5 stph) of massive quartzite based on a 2-min cycle time for hole drilling. Blasting with an ultrahigh -pressure hydraulic pulse generator was demonstrated as an effective means of excavating hard, massive rock under the confined conditions of a tunnel opening or underground sloping panel. Hydraulic blasting provides a continuous mechanized mining capability that is well suited for deep-level mining and urban excavation sites where explosives are prohibited.

Jan 1, 1998

By H. O. McDonald

The Bureau of Mines has demonstrated a hydrometallurgical method to separate chromium from other metals in a variety of surface-finishing wastes by precipitation with benzoate ion. The resulting chromium salt may then be converted to the hydroxide, and the benzoate may be recycled. Chromium recoveries of 92 to 100 pct are obtained.

Jan 1, 1983

By Thomas E. Ban, Charles D. Thompson, Charles A. Czako

Continuous sintering-a metallurgical process for more than 50 years-has broadened from its origin in nonferrous metallurgy to present-day applications in ferrous, chemical, and nonmetallic fields. During the past year, self-fluxing sinter production has been a subject of active interest to iron metallurgists in North America. Accomplishments however, have come predominantly from Europe and proper interpretation of these reports requires an understanding of European raw materials and European economics. The technology, of course, can be applied universally.

Jan 10, 1959

By P. B. Liebermann

THE resistance to motion offered by mine cars is caused principally by: Rolling friction, flange friction, bending rails, bearing friction and wind resistance. With proper construction and with a fair amount of attention and care, that is, under favorable conditions, the first three items cannot be greatly improved. The wind resistance ordinarily is negligible on account of the slow speeds commonly used. The bearing friction, however, is a variable item, depending upon the design, the bearing material, the lubrication, the location (whether in wheel-hub or on car-body) and the alignment. Under the most favorable conditions the bearing friction will reach a lowest possible value. By the development of a successful anti-friction mine-car bearing this lowest value has been improved to such an extent as to affect the whole system of mine haulage. After being satisfied of their durability and certainty of operation, any investigation into the advantages of anti-friction bearings for mine cars will have to be based upon reliable information as to the saving in power of such bearings. While numerous tests have been made in this direction, the results have not always been convincing, principally because of the rather crude methods that were employed. These crude methods are the main cause of the wide variations existing in regard to the exact amount of the frictional resistance. Frequently an ordinary spring balance is used and the pull necessary to move a certain car or train of cars is obtained by a number of readings. Such spring balances necessarily have a coarse graduation and the continuous vibration and fluctuations to which they are subjected make them highly dependent upon the individual observer. Further, they must be frequently calibrated. Sometimes these tests were made without regard to acceleration, speed or even grade.

Jan 6, 1916

By Arthur F. Taggart

In 1900, Elmore found that if an acidulated pulp was stirred up with an oil which was relatively insoluble in and lighter than water, and the mixture was allowed to stratify, much of the sulfide would be found hanging to the lower surface of the floating body of oil and could be skimmed off or overflowed with it. The action of the flotation agent here is twofold, first to select the sulfide from the gangue—what today is called collection—and second, to buoy the collected sulfide away from the gangue. The action in collecting is illustrated by Fig. 1: which contrasts the behavior of drops of oil brought, under water, to the surfaces of gangue and sulfide particles, respectively. The oil displaces water from the surface of the sulfide; the water displaces oil from the gangue surface. If, instead of considering the solid particles the fixed parts of the system of oil, water and solids. we consider the oil and water fixed and the solids presented to the surface of contact, the condition will be as shown in Fig. 2; the sulfide tends to be drawn into the interface and the gangue to be excluded. The sulfide particles are held in the oil-water surface by the tension of this surface. The buoyant effect is supplied by the oil droplets in bringing the sulfides to the water surface, but not in holding them there. Gas as Buoyant Medium of Flotation In 1906 Sulman. Picard and Ballot discovered a practical and substantially fool-proof method of doing what Everson, in 1886, and Fro-nlcnt. DeBavay Bessel and Elmore had been doing in the intervening years, viz.: using gas in place of oil as the buoyant medium for flotation, but retaining oil as the agent. To all of these inventors "oil," with no qualification as to its kind and no true understanding of its function, was the important thing. Hut they placed on the oil an additional burden viz.: froth-making, and it soon became apparent that not all oils were suitable for the dual purpose. As a matter of fact, it is probable that each of these inventors knew only one suitable oil at the time he wrote his patent, but used the generic term in the patent with the usual idea

Jan 1, 1928