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By P. A. Toynbee, D. G. Wilson

The combustion performance of sub-bituminous slack coal is greatly improved by the removal of the smaller size fractions. Screening processes are not well suited to the size separation, at 1/8 in. or 1/16 in., with coals which are normally wet, and the use of an alternative size-separation device has been investigated. It is felt that this classifier might be applied equally well to other minerals in cases such as this, where precise size limits are not essential. Coal is dropped as a curtain onto a curved metal plate, shaped rather like a ski-jump. The smaller particles, slowed up in their free fall to the plate and also by contact with the metal, leave the plate with a lower horizontal velocity; they can be separated from the larger particles by virtue of their shorter trajectory. The principle of the classifier is obvious from the diagram (see Fig. 1) which shows also the positions, relative to the curved plate, of the point of coal feed and of the dividing plate which separates the streams of coal particles. The horizontal distance between the curved plate and the dividing plate is varied in the tests. It is designated in the general case, by X. Tests were carried out using slack coal with a free moisture content higher than that expected in any commercial operation. The results given in Table I. show the percentage recovery of upgraded product, and the cumulative screen analysis of both the upgraded and reject material, for three different positions of the dividing plate. The results show, for example, that the original coal can be upgraded, with a recovery of 80%, to reduce the minus 1/8 in. frac-

Jan 1, 1965

By E. De Golyer

THE petroleum production of the world, in 1923, for the first time reached the billion-barrel mark. A preliminary estimate of production is 1,014,413,000 bbl., an increase of 159,604,000 bbl., or 18.6 per cent. over the 854,809,000 bbl. produced in 1922, the year of next highest production. This increase resulted from an increase of 178,469,000 bbl. in the production of the United States; the total for the rest of the world shows a loss of 18,865,000 bbl., a loss caused by the decrease of approximately 32,278,000 bbl. in Mexican production. The Mexican decrease more than offset increases in the production of Russia, Persia, Roumania, Venezuela, Sarawak, and various minor fields. The increase in production for the United States, and consequently for the world, was the result of flush production from development to maximum capacity during the year of eight, bonanza fields-fields reaching daily yields of 100,000 bbl. or better. It might be ascribed more exactly to the production from the three flush fields of the Los Angeles basin. Their production alone was greater than the increase in the world petroleum production, or the increase in the production of the United States, and it was cheap oil from these fields that demoralized the oil markets of the world. The Basin fields were. the features and dominating factors in the oil industry of the world during 1923. The bonanza fields of 1923, their estimated production for the year, and peak are given in Table 1.

Jan 3, 1924

By E. A. Steigerwald, G. L. Hanna

The influence of work-hardening exponent on the variation of fracture toughness with material thickness was studied for high-strength steel, aluminum, and titanium alloys. The results indicate that, when materials are compared at similar fracture toughness to yield strength ratios, the material with the lower work-hardening exponent undergoes the transition from flat to slant fracture at a larger thickness than material with a high work-hardening exponent. In the thickness range where complete slant fracture is obtained the reverse is true and a lower work-hardening exponent results in a lower fracture toughness. The influence of work-hardening exponent on fracture toughness is, therefore, dependent on the particular fracture mode. In the transition region a low work-hardening exponent is beneficial for fracture toughness while in the 100 pct slant region it is detrimental. THROUGH the use of fracture mechanics analyses, the influence of geometric variables on the crack propagation resistance of structures can be interpreted with reasonable consistency. However, in order to gain a more complete understanding of the fracture process, the influence of material parameters on crack propagation must be defined and coupled to the macroscopic fracture mechanics approach. The work-hardening exponent, which characterizes specific material behavior, may serve as an effective parameter to allow some degree of coupling to be accomplished. In the extension of a crack in a specimen of suitable dimensions the propagation process occurs in a stable manner when the crack extension force is balanced by the resistance to crack extension, which exists in the material at the crack tip. As the applied stress, and therefore the crack extension force, on the specimen increases, the resistance also increases primarily because the effective plastic zone at the crack tip, which is the main energy absorption process, becomes larger. Since the work-hardening rate of a material influences the stress-strain relationship, it will also influence the energy absorption process in the plastic enclave at the crack tip and hence should have an effect on crack propagation. A number of studies have been made correlating the strain-hardening exponent or the strain to tensile instability with the ability of a material to resist fracture. Gensamer1 concluded that a low-strain-hardening exponent would result in a steep strain gradient at the base of a notch. He reasoned that a large work-hardening coefficient would result in high-energy ab- sorption due to the increased area under the stress-strain curve. Larson and Nunes2 experimentally observed in Charpy tests on steels heat-treated to below 200,000 psi yield strength that the energy to failure in the fibrous mode, i.e., above the brittle-to-ductile transition temperature, was logarithmically related to the strain-hardening exponent. In order to avoid the complicating effects present in studying materials which undergo a brittle-to-ductile transition, Ripling evaluated the notch sensitivity of a variety of fcc metals with varying work-hardening exponents.3 The results indicated that the relative notch sensitivity, as determined from tests on specimens with a sharp notch, decreased with increasing values of strain hardening. Although the energy required for ductile or fibrous fracture increases with increasing work hardening, high-strength steels often exhibit improved crack propagation resistance when heat-treated to obtain low values of strain hardening.4,5 An analysis of whether low strain hardening is beneficial or detrimental to crack propagation resistance must depend on the particular fracture criterion involved. At temperatures where the material is relatively ductile and the development of a critical strain is required for fracture, high strain hardening increases the energy required to produce failure. In the transition region and below, however, a critical stress law appears to be valid6 and a low rate of work hardening may produce superior resistance to semibrittle crack propagation. The experimental program is aimed at studying these possibilities and determining the specific influence of strain hardening on the crack propagation resistance of several high-strength materials. MATERIALS AND PROCEDURE The alloys, chosen as representative of various classes of high-strength materials, are summarized in Table I. The heat treatments evaluated along with the smooth tensile properties are presented in Table 11. Pin-loaded sheet tensile specimens were employed to determine the smooth tensile properties. A strain gage extensometer (measuring range 0.200 in.) was used at a strain rate of 0.02 in. per in. per min. The work-hardening exponents were determined from the stress-strain curves generated in the smooth tensile tests and the assumption that the portion of the stress-strain curve beyond the yield point can be described by the power relationship: where a is the true stress, P is the true plastic strain,

Jan 1, 1969

By H. H. Pentz

THIS paper gives the derivation of a practical formula for the calcu-lation of slopes in seismic reflection prospecting. The derived formula is an approximation and can be used where the slope of the reflecting horizon is less than 250 ft. per 1000 and the depth to the reflecting horizon is greater than 2500 ft. The slope of sediments in oil regions is generally considerably less than 250 ft. per 1000. This is particularly true of the Gulf Coast, with the exception of the salt domes, which usually have the sediments at a greater slope than 250 ft. per 1000.

Jan 1, 1937

By S. Skowronski

The melting of cathode copper, ususally containing 95.98+ per cent. • Cu, would appear to be a simple matter. Owing to the well known affinity of copper for sulfur, however, so much sulfur is absorbed by the copper during the operation that a long and expensive refining process is required to remove it, and the final product is inferior in purity and lower in electrical conductivity than the original cathode copper. The furnace operation, as now conducted, includes the following stages: 1. Charging the cathodes into the furnace. 2. Melting the cathodes. 3. Oxidizing period—saturating the copper with cuprous sub-oxide and bringing the metal to the condition known as "set copper;'' this is now done by blowing air into the molten bath of metal. 4. Reduction period, otherwise known as "poling," whereby the oxygen previously added is removed by covering the molten bath completely with coke or charcoal and introducing large poles of green wood; this reduces the cuprous sub-oxide, bringing the copper to the "tough pitch" stage ready for casting. 5. Casting Period. Many experiments have been made to obviate the long periods of oxidation and subsequent reduction, with no success. While the copper first cast will be good, as indicated by the set surface of the bars, it is impossible to hold it to the "tough pitch" condition, and long before the whole charge has been poured the copper will become "overpoled," entailing numerous difficulties. Sulfur has always been blamed by the furnace men as the reason why this refining process is necessary, yet the literature on the subject does not sufficiently emphasize how small a proportion of sulfur will ruin copper for practical purposes. The sulfur absorbed by copper during the melting period comes from two sources: (1) the sulfate left on the cathode sheets in the tank houses; (2) the fuel. The percentage of sulfates on the cathodes is variable, and depends on the care taken in washing the cathodes after removing

Jan 1, 1919

By F. A. Howard, R. T. Haslam

In a broad sense automotive fuel is simply fuel in general and includes coal, coke, wood, charcoal and gas, in addition to the full range of liquid combustibles. All of these are actually used, or have been used, commercially to some extent as fuel for automotive vehicles. The steam lorry burning coal and coke is a common sight on the roads of England. The fact that these coal-fired steam lorries have a distinct advantage in taxes over the conventional gasoline-driven lorry probably explains the survival of this vehicle. The omnibus, or charabanc, operated by city gas carried in a balloon container on the roof, was also at one time a common sight in England, although not as common as the ubiquitous steam lorry. These gas-operated vehicles have, however, disappeared from the streets in recent years, and probably owed their existence entirely to war conditions. In France one of the largest motor vehicle manufacturers had last year more than 30 trucks equipped with regular gasoline engines in service in the Parisian area operating on producer gas obtained from a small gas producer mounted on the running board of the truck. Both wood and charcoal have been used in these gas producers. The authors were interested enough in this unique commercial development to spend some time examining the apparatus used and inquiring into the success which it had met. The picture is by no means an impossible one purely from the standpoint of practicability, but there is no doubt of the soundness of the conclusion that this is not a development which has any present important significance. Powdered carbonaceous matter, coal, coke or lignite, has been used experimentally in special forms of internal combustion engines, but so far as is known, these have never been applied to automotive practice. Range of Liquid Combustibles In the field of liquid combustibles the full range has been exploited to some extent. Heavy residual fuel oils from petroleum have been

Jan 1, 1928

By J. Goldfield

Asbestos fiber, before it can be used commercially, is separated from the rock in which it is naturally found. Johns-Manville Corp. is currently constructing a 12-story fiber mill, of which the first half is completed and in operation. The mill will be the largest in the world, producing about 30 pct of the world's fiber. It was engineered and constructed by a cooperative effort of the engineers of the Canadian Johns-Manville Fibre Div. and the general plant engineering dept. Detailed design work on all phases of the job was done by Surveyer, Ninniger & Chenevert of Montreal. A series of crushing, screening, air aspirating and air separating processes will separate the fiber from 10 tons of rock per min. But to process this amount of ore about 90 tons of air per min will be handled in the aspirating and dust-collecting systems. To express this in more common units, 2.5 million cfm of air will be required. All this air will pass through a bag-type continuous automatic filter and will be expelled to atmosphere in summer or returned to the mill for heating during the winter months.

Nov 1, 1955

By E. W. Johnson, M. L. Hill

The dijfusiuity D was determined at 25° to 780°C- from hyd?-ogen evolution rates. Anomalous evolution from air-melted iron was att~zbztted to residual hydrogen, which is interpreted as a hydrogen compound that decomposes at a strongly temperature-(Ieperzdent rate above 500°C. Above 200°C, D = 0.0014 cm2sec-1 exp (-3200 cal per g atom/RT). Below, 200°C the diffusivity is anomalously low and represented by D = 0.12 cm2sec-l exp (-7820 cal per g atom/RT). It is postulated that at low temperatures the hydrogen in the metal is "trapped" with an energy 4.8 kcaL per g atom below- that of the interstitial hydrogen. 1 HE purpose of the present experimental study was to determine the diffusivity of hydrogen in a-Fe over an extended temperature range. As certain anomalies were encountered, attempts were made to understand the anomalies themselves. This research was in progress both before and after a determination of the diffusivity of hydrogen in nicke1.l The latter system was found to exhibit none of the anomalies of hydrogen in iron, and its description was far simpler. The experiments on nickel also

Jan 1, 1961

By M. J. Bradley, P. H. Dike

THE art of melting nonferrous metals, in smelting, casting, and in compounding of alloys, is highly dependent on a knowledge of the temperature of the metal. This knowledge may reside in the experience and judgment of the melter, or it may be based on measurement by suitable instruments. It-is our purpose to discuss briefly the instruments available for such measurements, and more at length the present, practice in molten metals, without recommendation. In the limits of time and space allotted, we can do little more than mention the available methods of measurement that are directly applicable in this field. In the 1939 edition of the Metals Handbook, issued by the American Society for Metals, pages 285-310, there is a more extensive discussion of pyrometry than can be attempted here, which should be referred to for details we must omit. For reasons that will appear, thermoelectric pyrometry will constitute the major portion of our discussion of the subject, only limited attention being given to radiation or optical pyrometry. METHODS OF MEASUREMENT THERMOELECTRIC PYROMETRY A thermocouple consists of two dissimilar wires, or a wire inside a tube of a dissimilar material, joined together at one end, which is placed in the region or medium where the temperature is to be measured, while the other ends are connected through suitable lead wires to a voltage-measuring device, which may be a millivoltmeter or a potentiometer. An electromotive force is generated in the circuit, which is proportional to the difference in temperature between the hot junction and the junctions of the lead wires to the measuring instrument. If this latter temperature is maintained constant, the e.m.f. measured varies only with the temperature of the hot junction. Every thermoelectric pyrometer is calibrated for a particular cold-junction temperature such as 0°F., 32°F. or 75°F., but usually it is more practical to compensate instrumentally over the probable range of cold-junction temperatures than to maintain the junction at the particular temperature for which the instrument was calibrated. Thermocouple Materials Only a very few pairs of metals are in frequent use for pyrometric measurements. The most generally used are iron-constantan for temperatures up to 1500°F. in oxidizing and up to 1800°F. in reducing atmospheres and chromel-alumel, which may be used in oxidizing atmospheres at temperatures up to 2400°F. for intermittent service. The accuracy of the latter deteriorates rapidly at temperatures above 2200°F. Platinum vs. platinum-rhodium thermocouples may be used up to a temperature of 3000°F , but they are easily contaminated by slow absorption of

Jan 1, 1946

By J. Chipman, H. Towers, M. Paris

A simple radioactive tracer technique is used to measure the diffusion coefficient of calcium ion in molten slags. In a slag of 40 pct Ca0-40 pct Si0,-20 pct Al203, Dc " at 1450°C is 1.3x10-6 cm' sec-'. THE application of the principles of thermodynamics to steel and iron making problems has proved so fruitful that the kinetic approach has tended to be neglected. It seems probable that in some reactions the rate-determining step is the dif-fusivity of the reactants or of the products. But knowledge of the diffusion coefficients of the constituents of liquid slag and metal is singularly lacking. The present work was undertaken as a first step toward supplying such data for slags. Furthermore, any additional information on the physical properties of liquid slags might be expected to help in elucidating their structure. It is essentially a preliminary investigation, the course of which was determined more by the necessity of establishing a method than by the immediate intrinsic interest of the results. For example, the selection of calcium ion to be studied was dictated by the suitability of the isotope Ca45 in that it is a simple emitter with a long half-life. Of the other ions commonly encountered in slags, the isotopes of iron and manganese have relatively complex radiations as well as the normal disadvantage of requiring control of the oxygen potential of the atmosphere; Mg27 and Al29 have half-lives measured only in minutes; Si3' has a simple decay process but its half-life of 2.8 hr is too short for preliminary studies; the only useful oxygen isotope is the stable O18; and there remain only sulphur and phosphorus both of which have suitable isotopes but were rejected as being of less fundamental interest than calcium. Similarly a lime-alumina- silica slag was used in preference to calcium silicate primarily because of its low melting point and its capacity to form a glass on fairly rapid cooling. Literature Review Very few studies of diffusion in liquid silicate systems have been reported. In order to determine the origin of diopside inclusions in felspathic rocks, Bowen1 investigated the diffusion between diopside and various mixtures of albite and anorthite. Platinum crucibles were used with diopside, the heavier of the two liquids, forming the lower half of the cell and diffusion taking place against gravity. Change in concentration along the diffusion path was found by measuring the refractive index of the quenched glass. Nearly thirty years later McCallum and Barrett2 used essentially the same method to determine the diffusion coefficient of lime in lime-alumina-silica slags. In this case the interest was to find the rate-determining step in the process of slag attack on refractory materials. In an investigation of the kinetics of the sulphur reaction, Derge, Philbrook, and Goldman8 determined the diffusion coefficient of sulphur in a typical blast furnace slag by the simple procedure of melting a slag containing 2 pct S over an identical slag sulphur-free. They make no claim to a high degree of accuracy but suggest that D, is of the order of 10-6 cm2 sec-l. Other high temperature liquid diffusion studies have been concerned with metals. Holbrook, Furnas, and Joseph4 determined the diffusion coefficients of silicon, phosphorus, sulphur, manganese, and carbon in liquid iron by immersing a small carbon crucible containing pure iron-carbon alloy in a large vessel containing iron with a high concentration of the particular element. Their results were confirmed by Paschke and Hauttmann5 using a similar method. Diffusion coefficients in silicates in the glassy state have been studied by Johnson, Bristow, and Blau6 Both Na24 and Ca45 were used as tracers but only the

Jan 1, 1954

By M. Bourgon

The conductivity of liquid copper sulfide has been measured as a function of the mole fraction of sulfur in the melt at three temperatures: 1170°, 1250°, and 1300°C. The results show that a) the conductivity of copper-rich Cu,S is independent of the sulfur pressure in the furnace, and b) the conductivity of sulfur-rich copper sulfide increases rapidly with sulfur pressure. Assuming that the band theory is applicable to liquids leads to the conclusion that copper-rich copper sulfide is an intrinsic semiconductor, in which case electrons act as carriers. The activation energy for conduction in this case has been calculated to be 0.7 ev. On the other hand, sulfur-rich copper sulfide behaves as a p-type semiconductor, positive holes being responsible for conduction. IN order to elucidate the structure of Liquid copper (1) sulfide, Derge, Pound, and Osuchl have studied the electrical conductivity of this compound as a function of temperature. Their results showed that the conductivity is rather high, of the order of 100 ohm" cm", and that the temperature coefficient of conductivity is positive. This high conductivity seemed to indicate electronic rather than ionic conduction. This conclusion was checked further by Derge, Pound, and Yang,2 who measured the current efficiencies of copper sulfide melts at various temperatures. In all cases, the current efficiency was found to be nil, indicating the absence of appreciable ionic contribution to the conduction in

Jan 1, 1958

By Jock A. Campbell

Oil-impregnated rocks are known to occur in 22 of the 50 states. The largest known petroleum resources of this type are in Utah, with over 95% of the inventoried total, The Utah deposits are estimated to contain over 25 million bbl (42 gal per bbl) of oil in place.' All major Utah tar sand deposits crop out and can be mined partially by open pit methods, but in-situ techniques will have to be employed to recover oil from the deeper parts of the deposits. No significant development of Utah tar sands deposits for their petroleum content has occurred to date, although a mine and extraction plant are anticipated this year at Asphalt Ridge. The barriers to development have been mainly economic, but technological and legal problems will also have to be overcome.

Jan 5, 1975

By N. N. Clark

Pachuca tanks are used widely as reactors for treating gold slimes, and for alumina digestion and uranium leaching. In some designs, slurry mixing in the tank is achieved by introducing air at the base of a draft tube, which is the full height of the tank. A buoyant air-slurry mixture rises in the draft tube and is discharged at the top. The slurry flows back through the bulk of the tank volume. Little information is available to predict the relationship between slurry flow rate in the draft tube, and the volume of air added at the base of the tube. Most current designs are based on the energy balance proposed by Lamont 25 years ago. Recent two-phase flow theory is used to develop a momentum balance for the flow in the draft tube, and a new, accurate design equation is derived. Bubble slip, frictional (wall) losses, entrance losses, and acceleration effects all contribute to the pressure gradient in the draft tube. None of these factors may be neglected under typical operating conditions. The new design equation accounts for all of these factors, and finds good agreement with Lamont's experimental example. Also, the new equation demonstrates that it is uneconomical to operate the draft tube with high airflow rates.

Jan 1, 1985

By J. Gordon Parr, G. R. Purdy

The phase boundaries of "TiNi" have been accurately determined by high-tewperature X-ray diffraction and metallo-graphic techniques. The phase (centered at 51 pct Ni) has a restricted range of homogeneity at 500°C, and a much greater range at 800°C. "TiNi" in all alloys containing less than 51 pct Ni decomposes rapidly and reversibly at 36°C to form a previously unreported phase. ThE region of the titanium nickel system corresponding to the phase "TiNi" has been the subject of several investigations.1,2,4-7 Laves and wallbaum1 reported "TiNi" as a body-centered cubic (a2) Phase, and Duwez and Taylor2 determined its para- meter to be 2.986. Duwez and Taylor also reported that "TiNi" decomposed into "Ti2Ni" and "TiNi3" on prolonged heating at 650" and 800°C, which led McQuillan3 to suggest a sluggish eutectoid reaction between "TiNis" and "Ti2Ni". Margolin, Ence, and Nielsen,' working with higher purity alloys, found no evidence of this decomposition. They showed the "TiNi" phase region extending from 49 to 54 pct*

Jan 1, 1962

By Ed L. Reed

INTRODUCTION The most efficient development of a mine plan for in-situ leach (solution) mining must be based upon an understanding and application of the basic hydrologic characteristics of the aquifer containing the mineral values. Similar knowledge of the overlying and underlying aquifers is also required. This paper summarizes the hydrologic properties of a ground water system and describes some of the more important conclusions that can be drawn from a detailed hydrologic study. Basic to an in-situ leach mining operation is the flow of fluids through porous rock from place to place. The degree to which these movements of fluids can be predicted and controlled determines to a large extent the efficiency of the ore recovery operation. HYDROLOGIC CHARACTERISTICS The principal hydrologic characteristics of a porous medium (sand, intercrystalline or vuggy limestone, fractured basalt, etc.) influencing fluid flow are: Porosity Permeability Thickness Transmissivity Storage Coefficient Water Table or Piezometric Surface Hydraulic Gradient Briefly these parameters can be defined as follows: Porosity: the void space in a unit volume of rock. Permeability: the ease with which fluid will flow through a porous medium. Thickness: the height of the formation which contributes flow to a well. Transmissivity the product of permeability and thickness. Storage Coefficient. the volume of water released from the reservoir per unit drop in head. Water Table or Piezometric Surface: the level at which water will stand in a well: the top of the zone of saturation in a gravity aquifer; the height to which water will rise above the confining bed in an artesian system. Hydraulic Gradient the direction and rate of dip of the water table or piezometric surface. A properly designed pumping test will provide numbers for transmissivity, storage coefficient and the water table or piezometric surface. Drilling records or bore hole logs provide aquifer thickness data from which permeability can be calculated. Ground elevations applied to measured depths to water enable one to calculate the direction and rate of dip of the water table or piezometric surface. Porosity can be determined from core analyses or density logs; it can be estimated from grain size distribution curves in sands or sandstones and from, microscopic examination of drill cuttings derived from carbonate aquifers. CHARACTERISTICS OF FLUID FLOW The characteristics of fluid flow that are vital to an understanding of leach mining include: Velocity Direction Flow Path Radius of Influence The velocity of fluid flow is of paramount importance in planning and managing a leach mine operation. Velocity is directly proportional to the permeability and hydraulic gradient and indirectly proportional to the effective porosity The permeability determined from a pumping test is an average value for the interval stressed; therefore, the velocity calculated from data derived from a pumping test represents average conditions. Under actual conditions discrete portions of the aquifer open to the screen may have permeabilities several times as high as the average and minimum permeabilities only a fraction as much. An injection front will be irregular to the extent that the reservoir rocks are heterogeneous An important consideration is the direct relationship of velocity to head. A reservoir which would provide a velocity of 0.05 feet per day under conditions of equilibrium would allow fluid flow of 36 feet per day under typical leaching operations, i.e. 12-foot injection head, 12-foot pumping level and 50 foot five-spot pattern. The direction of fluid flow is also vital both inside and outside the mine area. In the pattern area the direction of flow is determined by the geometry of the well field and can be approximated by mathematical modeling techniques. Outside the well field, the direction of flow is influenced by both natural conditions and the degree to which production and injection volumes are balanced. Flow directions (and velocities) are critical to an understanding of leachate excursions and their control.

Jan 1, 1979

Spencer Gulf takes off from the Great Australian Bight cutting a 200 mile deep wedge of water into the South Australia coastline. A pale winter sun shines yellowly on the choppy surface of this body of water which is progressively more salty as it approaches Port Augusta at the head of the Gulf. Once Port Augusta thrived as a grain port and the speedy clipper ships began or ended their legendary races there. On the eastern shores of Spencer Gulf, farm land spreads away from the water's edge. The western side of the gulf meets marginal grazing land of acacia tree and salt bush. Part way down the gulf, there are two industrial towns facing each other from opposite shores; Port Pirie on the east and Whyalla on the west. These towns are like half brothers, the common parent being the founders of Broken Hill Pty. Ltd., (BHP) who began lead smelting at Port Pirie and discovered iron ore near Whyalla needed for the lead smelting process. The iron deposits later became the inspiration for BHP's iron and steel business.

Jan 10, 1964

By Stanley L. Arnot

The Mother Lode district in California is probably better known as the land of Bret Harte and Mark Twain than as a gold-producing district, although in this respect it holds an important place. The history of quartz mining on the Mother Lode dates back to the '50s, when, after the first fever of the gold rush, men began to look for something more permanent, if not more lucrative, than the placers. Since that time, the discoveries, shutdowns, and reopenings of the many mines, together with the varying fortunes of their numerous operators, constitute an interesting chapter in California history, but one too long to include in a description of mining methods. The district is well situated, so far as physical conditions are concerned. The Mother Lode extends along the western slope of the Sierra Nevada Mountains, about half way between the crest and the Sacramento and San Joaquin Valleys, the country traversed consisting of low rolling hills—typical foot-hills. The elevation varies from 1000 to 1800 ft. and the climate is most desirable. There is an abundance of water, timber is easily obtained from the higher foot-hills a few miles east, and cheap hydro-electric power is generated practically on the Lode. These natural conditions are conducive to low costs in mining and have been the deciding factor in allowing profitable exploitation of the comparatively low-grade orebodies. Transportation facilities are not bad. Five branch railroads, from the main trunk lines in the valley, tap the district at intervals of from 10 to 30 miles, and the roads connecting these are fairly good for trucking purposes. Labor is made up of several nationalities, the principal ones being American, Spanish, Jugo-Slav, Italian, and Mexican. There were few Mexicans on the Lode prior to 1919, but the shortage of labor, experienced generally by the mining camps of the country in the years following the war, made necessary the hiring of some. The percentage of Mexican labor rapidly increased in 1920 and for a year or so thereafter, but it has now diminished until at most of the mines only a few Mexicans are working. Of the different nationalities, Americans are the most efficient and Mexicans the least.

Jan 1, 1925

By Constantine Michalopoulos, Roger C. Van Tassel

Commercial demand for gold in the United States is important. It has a large impact on the total world commercial and overall non-monetary demand. Given the present free market price and our need to import gold, it has a substantial adverse effect upon our international payments position. But, according to most recent estimates, the United States demand is perhaps no more than 20% of the world as a whole. In 1971, United States consumption was estimated at 215.6 tons out of a total of 1,412.1 tons 1. This figure is very close to the 16% figure developed by Consolidated Gold Fields as the average for the years 1968-1970.2 Surveys of both production and use of gold on a world-wide basis are not new. With the bulk of gold production in only a few countries, it has been possible to develop fairly reliable series on gold output. Estimates have been developed on the known reserves of gold and probable output at various prices.3 On the demand side, figures have been somewhat less complete and reliable. The Bank for International Settlements and the Director of the United States Mint have regularly published estimates of commercial use in major industrial countries. The IMF has issued an increasingly comprehensive survey in its Annual Reports. The IMF has attempted to cover all nations-not restricting its efforts to major industrial nations-and has tried to estimate both gold taken for commercial uses (Estimated Industrial and Artistic Use) and for private hoarding. Their method is to begin with data on free world output plus any net sales by the Soviet Union, subtract any additions to world monetary stocks (or add to available supply for any net reductions in world monetary stocks), subtract estimates for commercial demand and have left as a residual an estimate for private hoarding. The method is straightforward and simple but the quality of the data is suspect. Industry sources tend to believe the figures as biased on the low side because of a persistent tendency to underreport gold movements.4

Jan 3, 1974

By C. W. Sherman, John Chipman

IN the mathematical statement of the law of mass action, the activity of each substance consumed or produced in a reaction is used to obtain a numerical constant which is characteristic of the equilibrium of that reaction at the given temperature. The activity in many cases is equal to, or proportional to, the concentration. If this is the case, any units denoting concentrations, such as weight percentage or mol fraction, may be substituted in the equilibrium expression. It is even permissible to use mixed units provided only that each unit is that used in defining the activity of the corresponding substance. The indiscriminate use of concentration units in writing equilibrium constants sometimes leads to very erroneous results. On the other hand, what appear to be contradictory results from similar investigations often might be resolved if the activity is the quantity that is used to determine the equilibrium constant for the reaction in question. De-sulphurization serves as an important illustration. Sulphur in lron and Steel The control of the sulphur content of the finished product is one of the oldest and broadest problems in the metallurgy of iron and steel. In general, this control must be exercised through the action of a slag, and for this reason experimental studies of the distribution of sulphur between slag and metal have assumed considerable importance. Under slags of the type found in the basic open-hearth furnace the ratio (% S)/[% S] does not in general exceed about 8. Under blast-furnace conditions, however, de-sulphurization ratios of 50 to 100 are readily obtained, and under laboratory conditions using similar slags, the ratio may be as high as 400. The fact that blast-furnace metal is much more readily desulphurized than is molten steel rests upon two distinct phenomena. The first of these is connected with the slag reaction. In the open-hearth furnace, the equilibrium in the following reaction places a definite limit on the sulphur content of the slag: S + 0-- = 0 + S- - where the symbols underlined indicate elements dissolved in the liquid metal, while slag constituents are represented as ions. The high oxygen content of the open-hearth bath prevents this reaction from proceeding far enough to effect good desul-phurization. In the blast-furnace process, however, the oxygen activity is limited by the presence of carbon in the metal and in the coke bed and the controlling reaction becomes: S_+O- + C_=S- + CO(gas) [2] The second phenomenon which contributes to the easier desulphurization of blast-furnace metal is the effect of high concentrations of other elements. These elements, notably carbon, silicon, and phosphorus, increase the thermodynamic activity of sulphur several fold. As a result of this increase, the escaping tendency of sulphur from the metal phase is increased and its removal facilitated. Previous Studies It becomes, therefore, a matter of importance to determine the effects of various elements upon the activity of sulphur in the melt. The experimental approach to this problem has been made through the equilibrium between sulphur in the melt and gaseous atmospheres containing hydrogen and hydrogen sulphide. The reaction and its equilibrium constant are written as follows: S + H2(gas) =H2S(gas);K1 = -- [3] Pn2 • as where the symbol a, represents the activity of the sulphur in solution in the metal. The understanding of the chemical behavior of sulphur in steel and pig iron rests on a firm knowledge of the binary system Fe-S. A number of studies of the equilibrium have given closely agreeing results from which the activity and free energy of the dissolved sulphur may be found. The recent paper by Sherman, Elvander, and Chipman1 includes a discussion and quantitative comparison of the results of several of the significant researchesr-" on dilute solutions of sulphur in iron. The results of this study indicate that the relationship between the ratio Ph,s/p+ and the percentage of sulphur in solution is not a linear one. This

Jan 1, 1953

By Gerald Sherman

MINING asbestos ore by caving at Thetford Mines, Quebec, has been described in the Transactions of the Canadian Institute of Mining and Metallurgy in papers presented by the staffs of The Asbestos Corp. Ltd., in 1934, and Johnson's Co. Ltd., in 1941. The production by caving prior to 1949, in round figures, has been 14,500,000 tons of ore by The Asbestos Corp. and 5,500,000 by Johnson's Co. They are the only caving operations in asbestos at the present time. The Jeffrey mine of the Canadian Johns-Manville Co. at Asbestos, 40 miles southwest of Thetford, is well along in preparations for caving, and The Bell Asbestos Mines Ltd. at Thetford Mines, will follow their examples later. GERALD SHERMAN, Member AIME, is Consulting Engineer, Johnson's Co. and Canadian Johns-Manville Co., New York, N. Y. AIME San Francisco Meeting, Feb. 1949, and New York Meeting, Feb. 1950. TP 2828 A. Discussion (2 copies) may be sent to Transactions AIME before May 31, 1950. Manuscript received Nov. 2, 1949. Nearly all of the asbestos produced by the western hemisphere is mined in those districts of Canada. Since it has been the subject of a number of technical papers, this contribution is offered as a review of progress. Some introductory information seems appropriate, for few members of the American Institute of Mining and Metallurgical Engineers are familiar with the mineral, or how asbestos deposits differ from others in caving characteristics. Asbestos is found in peridotite, a basic intrusive rock irregularly altered to serpentine and erratically fractured, well enough to cave in bulk, but leaving many blocks of solid ore of all sizes scattered through the deposit. Chrysotile is the variety of asbestos produced in Canada. Its fibers are the most valuable commercially, having a good proportion of long fibers, strong, silky, flexible, and suitable for spinning. The fibers occur in all lengths, from the microscopic to 3 in., or more, the shorter are more abundant. Their values depend on length combined with other qualities noted above. They occur as veinlets filling fissures in the peridotite, with crystals compactly arranged in parallel across the cracks. They are sometimes lightly frozen to the walls but the partings are distinct, often marked by particles of magnetite adhering to the fiber ends. Sometimes they break away from the rock in slabs an inch or more in thickness. In wide fissures the fibers are not always continuous, the "broken fibers" being separated by lines of parting with occasional scattered grains of magnetite, which is an injurious mineral to be elirninated when possible. In addition to the chrysotile ''Cross fiber," some "slip fiber" is found in fault fractures in limited quantities of less valuable character. With the exception of the Asbestos Corp, ore, in which the content is said to be more uniform, asbestos is eccentrically distributed through the peridotite. It is the general impression that the higher grades are more often found in hard rock. There are rich pockets and leaner areas which range down through various grades to minor barren sections. Wholesale mining is necessary to make sure of recovering all the high grade for there are no reliable indications of its existence. Ore selection only appears in constructing assay-grade limits for caving. The mill yield of the Thetford ore body in 1934 was 6 to 10 pct of the ore milled, made up of all classes, with occasional runs up to 15 pct or so. Quotations for Canadian asbestos* are as follows: Per Ton No. 1 Crude (% in. and longer) $896 @ $960 No. 2 Crude (Y8 to % in.) 350 @ 545 Spinning (less than % in.) 204 @ 378 Other classes, price diminishing with length. Shorts or "refuse" 24 @ 46 • From Eng. and Min. Jnl., Nov. 1948. Asbestos of even superior quality for electric insulation is found in Arizona limestone. It is white, containing very little combined iron, but occurs only in small quantities.

Jan 1, 1951