Search Documents

By R. G. Garlick, M. Garfinkle

It was observed for several bcc metal crystals that the Knoop hardness anisotropy was dependent essentially on the direction of the lung axis of the indentor alone and not on the plane of indentation. The generality of this observation was tested for an fcc md an hcp metal and an ionic crystal. For cubic crystals, this observation was valid; for the hcp structure, however, the planes of indentation did have an effect on the hardness anisotropy, although this was not nearly as significant as the direction of indentation. Because the direction of indentation is the only significant crystal-lographic parameter necessary to describe the hardness anisotropy, it is possible to represent the anisotropy of single crystals on the standard stereographic triangle. THE commonly observed1, 2 periodic variation of indentation hardness with crystallographic direction on the high-symmetry planes of various single crystals has been inadequately related to the physical or mechanical properties of the crystals examined. In fact, the hardness anisotropy curves for the various planes of a particular metal crystal, as is illustrated in Fig. 1, are uncorrelated and appear in the literature3, 4 as unrelated observations. Attempts to correlate hardness anisotropy curves with specific physical properties can be generally divided into either mechanistic or nonmechanistic approaches. A nonmechanistic approach would be to devise a mathematical expression that could describe the various hardness anisotropy curves. Such a relation could then be compared with the known anisotropy of various physical properties to determine which contribute to the observed hardness anisotropy. No such mathematical expression has been found in the literature.

Jan 1, 1969

By A. Filyk

The current plant practice at Molycorp, Inc., Questa Division, a molybdenum producer in northern New Mexico, is described. An outline of crushing, grinding, flotation, drying, and tailings disposal is included, with emphasis on metallurgy.

Jan 1, 1976

By Helen L. Cannon

BOTANICAL methods of prospecting for metalliferous ores are based on the premise that deposits at depth may be reflected chemically in surface vegetation. For the past several years, on behalf of the Atomic Energy Commission, the U. S. Geological Survey has investigated on the Colorado Plateau the application of botanical methods to uranium prospecting. Results suggest that orebodies may be found under a considerable cover of barren sandstone through the absorption of uranium and associated trace elements by plants growing at the ground surface. Plant physiologists have demonstrated that uranium is a necessary nutrient for plant growth and therefore is present in all plants.' The amount present is small but measurable. The absorption of uranium by plants growing over ore deposits forms

Jan 1, 1955

By J. C. Mertz, C. H. Mathewson

Accurate knowledge of the solid solubilities of the elements that dissolve in the important base metals is needed for guidance in the preparation and heat-treatment of the alloys derived from these components. While there is still difference of opinion concerning the merits of the X-ray and microscopic methods of determining such solubilities, it is certainly true that the recent extensive use of X-ray diffraction to review the existing constitutional data has revealed many glaring inaccuracies and has brought about a much improved knowledge of phase-boundary locations, which will inevitably come to include all of the important alloy systems. When the work is done with all necessary precautions it appears that in the majority of cases where the solubilities extend beyond a few tenths of a per cent the X-ray back-reflection technique is capable of furnishing the best of information in this field. For the most prolonged and thorough studies it is obviously advisable to combine the results of several methods, in particular, to obtain an agreement between X-ray and microscopic data. This paper reviews the work previously done on the solubilities of phosphorus, arsenic, antimony and bismuth in copper and, in consideration of the uncertainties thus made apparent, presents new X-ray data obtained with the first three members of this group. Copper-phosphorus System Heyn and Baurl found that in slowly cooled alloys phosphorus forms a solid solution with copper up to about 0.175 per cent. Huntington

Jan 1, 1937

By John Cogan, P. M. Gomez

A typical problem in applied rock mechanics is an accurate prediction of support requirements for deep rock cuts. This paper presents experience with this problem as obtained from excavations for a powerhouse at the Pine Flat Dam near Fresno, California. The project, sponsored by the Kings River Conservation District is still under construction. Highly jointed and weathered rock was discovered during initial excavation. Wedge failures along clay filled joints and bedding planes presented potential support problems. Detailed mapping of joints and beds was undertaken to establish basic patterns of all rock discontinuities including mean orientations and an estimate of orientation variations. Rock bolting patterns were devised to meet these patterns as excavation proceeded. Shear friction angles across joints and beds were estimated from rock wedge fallouts. Friction angles as low as 27º were identified on highly weathered joints. Weathering strongly influenced stability conditions. Examples of bolting patterns to stabilize critical slopes are presented.

Jan 1, 1982

By P. W. George

THE rapid increase in cost of discovering new orebodies by churn drilling in the Tri-State district has led to some attempts to lessen the expense by using geophysical methods. Electrical prospecting was tried three or four years ago, but no successful results were recorded. In 1926, the Federal Mining and Smelting Co. engaged the North American Exploration Co., of Houston, Texas, to make some tests with the torsion balance. At first, it was thought that the most favorable conditions for discovery of ore deposits with the torsion balance would be in locations where the ore was known to occur at rather shallow depths, FIG. 1.-CROSS-SECTION OF DUENWEG LEASE. therefore the first trial was made at Duenweg, east of Joplin, where some zinc ore had been developed at a depth of 130 ft. The gravity gradients at 61 stations on a tract of about seventeen acres indicated plainly one large zone of maximum gravity and a smaller narrow zone of minimum gravity. Fourteen churn-drill holes, half of which struck ore, show that all the ore found was located outside the zones of maximum and minimum gravity. In the zone of maximum gravity the limestone beds were closest to the surface, and the first chert beds encountered were at the greatest depth. The results (shown in Table 1) indicated that the gravity of the, limestone was greater than the gravity of the fractured chert together with its orebodies, and probably also greater than the bouldery soil and clay on top of the limestone. A cross-section of the Duenweg lease is shown in Fig. 1.

Jan 1, 1928

By R. Schutte, L. W. Trevoy

Commercial production of heavy minerals from plant tailing streams is undergoing study by Syncrude Canada Ltd. When tar sand from an open pit mine is processed and upgraded to synthetic crude oil, heavy minerals can be recovered from the extraction circuit and can be upgraded to provide concentrates of zircon and titanium minerals. The titanium minerals concentrate, consisting of a mixture of ilmenite, leucoxene, and rutile, can be utilized as recovered or can be upgraded to synthetic rutile. With the construction of further synthetic crude oil plants in Western Canada a large reserve of heavy minerals will become available for production.

Jan 1, 1983

By J. T. Jones, H. V. Winchell

In the history of mining in this country there has been nothing exactly similar to the Mesabi iron-range in Minnesota, and the conditions there prevalent. Soft-ore mines are found in many parts of the country. In some the deposits are vertical, and are worked in open pits, or have been so worked, until it was found cheaper to go under ground. In other localities, the ore is scattered through clay beds in the form of hard lumps. These clay beds are sometimes excavated in open pits, and the ore separated by washing. On the Mesabi, the ore itself occurs in strata, and these strata appear quite flat to one standing upon the ground. The ore is soft in the main, and does not require much sorting to free it from foreign or deleterious substances. It is usually covered by the glacial drift-mantle, but occasionally passes beneath a capping of jasperoid rock called " taconite." The ore is twice or three times the thickness of the layer of drift lying upon it. This drift consists of clay, sand, and gravel, with occasional beds of large boulders. There is great difference of opinion among competent miners as to the cheapest methods of mining this ore. It is admitted that local conditions will govern largely ; but there is such a similarity among many of the mines that it seems possible to arrive at some general conclusions on the subject. A typical example of a Mesabi mine is found in the Biwabik. It is one of the largest, and is the most advanced in development. Not a single ton of ore has yet been shipped from this mine, but the expense of the explorations upon which the following description is based has exceeded $60,000. It is seldom that such accurate and complete exploration of a deposit of this magnitude has been possible in the space of time which has elapsed since the discovery of this ore-body. It lies in a new. region, and was remote from railroads until last August, yet, not only the width and length but the depth and quality of the ore-deposit have been learned, and the probable expense of' mining its 20,000,000 tons of ore has been closely figured. After careful consideration, the method of stripping and

Jan 1, 1893

By W. C. Lilliendahl, H. W. Highriter

The method developed and used in this laboratory for the production of metallic uranium of such purity that it is ductile and can be cold-worked to fine wire or thin sheet by rolling has already been described1. It consists, briefly, in the electrolysis of potassium uranous fluoride (KUF5) in a molten bath composed of equal parts of sodium and calcium chlorides. The bath is contained in a graphite crucible, electrically heated to about 775° C., the crucible serving as the anode for electrolysis. The uranium deposits in finely divided form mixed with salts upon a molybdenum cathode suspended axially in the crucible. Upon completion of the electrolysis the cathode is removed and cooled, the deposit broken and leached to remove salts. The metal powder is washed with water and dilute acetic acid and dried in vacuo to reduce oxidation. Suitable amounts are then prcssed into pellets and heated in vacuo by high-frequency induction, using a thoria crucible. The uranium melts and flows away from the pellet, leaving a shell, which is largely oxide. In general, this method produced a satisfactory metal, although at times tile uranium was not ductile. The investigations recorded here were made to find the cause of this embrittlement. It was known that the metal generally contained carbon, derived from disintegration of the graphitc crucible in which electrolysis is conducted, in amounts dependent upon the thoroughness of washing the metal powder. Accordingly, analyses of several samples, both ductile and brittle, were made by combustion and absorption of CO² in Ascarite, using air instead of oxygen to reduce the temperaturc and rate of oxidation. Several of these metals were made with special precautions to reduce carbon content. The results show no relationship between ductility and carbon content in the range investigated (Table 1). Microscopic examination of ductile and brittle metals disclosed the presence in the latter of an intergranular constituent, harder than the matrix and less easily oxidizable, which was absent from the ductile material. Rough estimates of the volume of the hard constituent

Jan 1, 1935

By W. C. Lilliendahl, H. W. Highriter

The method developed and used in this laboratory for the production of metallic uranium of such purity that it is ductile and can be cold-worked to fine wire or thin sheet by rolling has already been described1. It consists, briefly, in the electrolysis of potassium uranous fluoride (KUF5) in a molten bath composed of equal parts of sodium and calcium chlorides. The bath is contained in a graphite crucible, electrically heated to about 775° C., the crucible serving as the anode for electrolysis. The uranium deposits in finely divided form mixed with salts upon a molybdenum cathode suspended axially in the crucible. Upon completion of the electrolysis the cathode is removed and cooled, the deposit broken and leached to remove salts. The metal powder is washed with water and dilute acetic acid and dried in vacuo to reduce oxidation. Suitable amounts are then prcssed into pellets and heated in vacuo by high-frequency induction, using a thoria crucible. The uranium melts and flows away from the pellet, leaving a shell, which is largely oxide. In general, this method produced a satisfactory metal, although at times tile uranium was not ductile. The investigations recorded here were made to find the cause of this embrittlement. It was known that the metal generally contained carbon, derived from disintegration of the graphitc crucible in which electrolysis is conducted, in amounts dependent upon the thoroughness of washing the metal powder. Accordingly, analyses of several samples, both ductile and brittle, were made by combustion and absorption of CO² in Ascarite, using air instead of oxygen to reduce the temperaturc and rate of oxidation. Several of these metals were made with special precautions to reduce carbon content. The results show no relationship between ductility and carbon content in the range investigated (Table 1). Microscopic examination of ductile and brittle metals disclosed the presence in the latter of an intergranular constituent, harder than the matrix and less easily oxidizable, which was absent from the ductile material. Rough estimates of the volume of the hard constituent

Jan 1, 1935

By Michael Chender

The current outlook for financing new copper production is not very encouraging. At a time when companies are slogging through a protracted period of low prices as well as having to accept lower profits due to more stringent tax and royalty schedules, banks are beginning to require companies to take a greater equity interest in new projects. Mineral resource financing, including copper, seems to have lost much of its appeal to the lending institutions, and loans of any kind to many of the developing countries -from which over half of new copper capacity could be expected to come-are being examined much more critically than they were in the late 1960's and early 1970's.

Jan 12, 1976

By L. D. Jaffe

From data found in the literature, a method has been derived for calculating hardenability of titanium alloys from their composition. A single graph gives the contributions of each alloying element. These are simply added to a base hardenability for unalloyed titanium. Results agree satisfactorily with measured harden-abilities. RECENTLY the importance of hardenability of titanium alloys in permitting attainment of high strength and hardness has become apparent. If a titanium-base alloy has adequate hardenability for the section size and quenching practice used, it can generally be heat treated to high strength and hardness either by simple quenching or cooling from temperatures near the ß transus, by quenching and tempering (aging), or perhaps by direct isothermal transformation of ß1,2 If the hardenability is inadequate, high strength cannot be attained. Preliminary charts translating hardenability requirements for shapes quenched in various media into terms of Jominy end quenched hardenability specimens or ideal round sizes are now available for titanium alloys." The method proposed in 1942 by M. A. Grossmann for calculating hardenability of steels from composition has proved to be of great practical value.' It appeared worthwhile to see whether, using information available in the literature, a corresponding method for calculating hardenability of titanium-base alloys could be derived. Data No systematic experimental study of the hardenability of titanium-base alloys has yet been made. There is available, however, a considerable quantity of scattered data bearing on hardenability. Some investigators determined Jominy curves on one or several alloys. Others reported as-quenched hardness for specimens of a few alloys cooled at various rates or in various media. Still others gave the as-quenched hardness for systematically varied composition, using one or several cooling mediums. The measurements utilized in this work were limited to hardness. Strength measurements were not used because a low strength may reflect high hardness combined with brittleness. Since, in general, the hardness of titanium alloys goes through a peak as the cooling rate is varied from extremely fast to extremely slow, the cooling conditions at which peak hardness was found were taken as the measure of hardenability.1,2 When as-quenched hardness was found to drop as the content of an alloying element (believed to increase hardenability) was raised, this was taken as an indication that the cooling rate was faster than that giving peak hardness; otherwise, the hardness should go up because of solid solution hardening. Also, if the hardness increased on tempering at low temperatures, this was again taken to indicate that the cooling rate had been faster than that giving peak hardness. Many of the data did not indicate precisely the cooling conditions for peak hardness but merely set a maximum or a minimum bound, or a bracket. Since the sizes of specimens quenched and the location of the hardness readings were not always given, it was occasionally necessary to estimate reasonable limits for them. Only the nominal compositions were available in some cases. As quenching from below the ß transus is equivalent to starting with a mixture of a and ß phases, whose individual composition would differ from the overall composition of the alloy, only measurements after quenches from above the ß transus were used. Hardness measurements on samples heated during metal-lographic mounting were also discarded. Because of their bulk, the data used will not be reproduced. They have been or will be published elsewhere.5-22 Approach All data were first translated into terms of ideal round size. For conversion from Jominy or quenched round or sheet, the author's graphs were used." For a few furnace cools or helium quenches where cooling rates were given, conversion was made on the basis of equal cooling coefficient.23 Plots of ideal round size for peak hardness against percentage of alloying element were next made for

Jan 1, 1956

By F. W. Jessen, R. W. Durie

The dissolution of salt in the development of salt cavities is controlled by free-convection boundary layer flow along the salt surfaces. It is the purpose of this paper to expand upon results published previously, and primarily to illustrate the influence of surface features on the boundary layer and hence the dissolution process in the development of underground salt cavities. General dissolution equations are presented that apply to a surface inclined to the vertical. A salt surface inclined so as to be overlain by water is dissolved by boundary layer flow, while an inverted surface is dissolved by a combination of boundary layer and cellular flow. Detailed investigation of the boundary layer was limited to laminar free-convection flow. Truly laminar free-convection boundary layer flow may be encountered only in laboratory solution cavities, but the boundary layer will control dissolution even where cavity dimensions are such that free-convection turbulence will occur. The factors found to significantly affect the laminar boundary layer will affect dissolution with a turbulent boundary layer. INTRODUCTION Underground salt cavities have been used extensively for the storage of LPG products, and the use of these cavities is expanding each year. The increasing requirements for such cavities suggest the need for a better understanding of the mechanisms involved, for the purpose of the control of cavity geometry and the most effective use of the injected water. A previous paper outlined a quantitative approach to the determination of salt dissolution rates in the laminar free-convection dissolution of salt. It is the purpose of this paper to expand upon the results previously published and to point out significant factors in the application of these results to the dissolution of field cavities. The dissolution of salt in laboratory scale cavities is controlled by the free-convection boundary layer, which is the region of flow along the salt surface caused by the difference in buoyancy forces resulting from the salt dissolution. The transfer of salt into solution at the salt face causes an increase in salinity, and hence a greater density, in the water at the salt surface. The region of higher density tends to fall through the lighter, less saline water and a flowing boundary layer is the result. The water remains stationary at the contact with the salt surface,l so the resulting velocity profile is such that the influence of gravity is opposed by a viscous shear force at the salt surface. For salt to be transferred into solution from a solid surface to a boundary layer of fluid, it must diffuse through a stationary film of water at the salt contact. According to Fick's first law, the rate of mass transfer by diffusion is the product of the diffusion coefficient and the concentration gradient, with diffusion transfer in the direction of decreasing salinity. Once the salt has passed into the boundary layer, it will be transferred by a combination of molecular diffusion and convection. The convection transfer will in turn affect the rate of dissolution by influencing the gradient of the salt concentration at the surface. In the previous investigation by the authors to determine the basic mechanism of the salt dissolution process, an equation was developed that agreed very well with the experimental rates of free-convection salt dissolution from a smooth vertical surface. The technique was taken from the work of Eckert2 in the analogous heat transfer system and will be referred to as the integral method. The rate of salt transfer from a vertical section of height H was found to be:

Jan 1, 1965

By M. J. Buerger

Possibly the most puzzling features observed during a single-crystal deformation test are the appearance of slip striae on the surface of the crystal and the strengthening of the specimen.' While the first phenomenon is mainly of theoretical interest, the latter is fundamental to all strain-hardening and cold-working processes in which the deformation occurs by translation. The plastic deformation of crystals has received considerable discussion2 and need not be reviewed here in any great detail. It has been observed, essentially, that after a certain amount of. initial stress is applied, the surface of the crystal becomes covered with sets of parallel striae or rings which appear to divide it into thin slabs or slip blocks.3 The striae are the traces of rational crystallographic planes along which shearing movements are localized, these movements providing the strain which accompanies stress applied beyond pure elasticity. As deformation under the applied stress proceeds the slip blocks shear past one another, although the essentially single-crystal character of the specimen is unimpaired. All of the shearing apparently takes place in the immediate vicinity of the original slip striae without the appearance of new planes of movement.4 Since each increment of strain is attended by an increased stress requirement to continue the deformation, the crystal strengthens during the process.

By J. Skrove, C. R. Boardman

In situ permeability of the rock outside the Hardhat chimney was determined by pressurization of long holes with air. Experimental data indicated a remarkable difference between fracture permeability of the rock near the chimney and that at a considerable distance. Although permeable fault zones were known to exist in the granite stock, the measurements of background permeability were quite low, on the order of tenths to several millidarcies. The observed difference is about two or three orders of magnitude above this background in the region 125 to 215 ft radially from the shot point, or 80 to 165 ft radially from the vertical axis of the chimney. The presence of a collapsed drift immediately beyond this region precluded measurements which could have defined the maximum extent of the zone of high permeabilily. INTRODUCTION Previous exploration has revealed that contained nu-clear explosions create cavities which generally collapse, resulting in rubble-filled chimneys and annular fractured zones. These geometries have been shown to result in complex flow regimes which should increase the production rate from hydrocarbon reservoirs.' Empirical scaling equations have been developed for estimatina chimney radii and heights for a variet; of rock media.' The exten; of the annular fractured zone has been documented and associated permeability changes have been observed qualitatively for several explosions. This study was begun to establish the nature and magnitude of the permeability of the latter region. It is anticipated that results will be useful in estimating permeability changes and consequent production stimulation which might ensue from a contained explosion in a hydrocarbon reservoir. The post-shot environment of the Hardhat event (a 5-kt contained nuclear explosion in granitic rock) was c'hosen for the experimental measurements. The Hardhat device was detonated at a depth of 939 ft, and subsequent exploration revealed a chimney of broken rock with a radius of 65 to 70 ft and a height above shot point of 281 ft.' BeFore the explosion, the Hardhat medium was highly jointed and fractured (Fig. I). Jt was expected that differential rock motion along these and other weaknesses induced during cavity growth and collapse would significantly alter the permeability of the rock mass. EXPERIMENTAL METHOD Initially, three 2-in. diameter holes (Nos. 10, 12 and 19) were drilled about 25 ft outward through the walls of the 500-ft level drift (elevation 4,253 ft, Fig. 2). One was drilled near the chimney and two holes, one vertical and the other horizontal, were drilled near the shaft. Order-of-magnitude differences in permeability obtained by pressurization measurements indicated further: investigation was warranted. A series of 3-in. diameter holes was then drilled with water as a coolant into the walls and roof of the drift (Fig. 2). An 11-in. long packer was set from 1 to 8 Et inside each hole and air was injected at measured Row rates. Hole pressures were monitored at the collar. Permeability was low enough in the holes near the access shaft that pressure could be maintained long enough to obtain good pressure decay rates. In the vicinity of the chimney, however, permeability was so high that this was not possible and air was injected under steady-state conditions. About one year later, these same holes were retested to

Jan 1, 1967

By Spencer Cragoe

I have read with much interest the elaborate and able paper of Messrs. Granger and Treville on the Mining Districts of Colombia, presented at the Atlantic City Meeting (ante, p. 33). Going into detail, however, as the paper does—and particularly with reference to the department of Antioquia, I am somewhat surprised that the property of the Frontino and Bolivia Company, probably one of the richest and most extensive in Colombia, should come off with such scant notice. The entire property embraces an area of some 28 square miles, and is situated at a distance of about 2 leagues from Remedios—after Medellin probably the most important town of the Department—and lying in approximately '7° N. latitude. The neighborhood of Remedios has been long celebrated for its production of the precious metal. Alluvial gold in large quantities has been obtained from the vicinity for upwards of two centuries; and even to-day a large proportion of the population finds a comfortable livelihood, during the dry season, in washing the sands of various rivers, notably the Rio Porce; while the amount of gold, in the form of nuggets, brought almost daily to Remedios and other points, from streams in the immediate neighborhood, is astonishing. These nuggets vary much in size. The majority, of course, are small, but larger ones are by no means scarce. I have been considerably surprised at the amount and value of the trade thus transacted between natives and merchants of the various towns. The property owned by the Frontino and Bolivia Company has been, I believe, for the larger part of the present century,

Jan 1, 1899

By G. H. Jardine

In future years, decision makers in the coal industry will make more and more decisions based on information from computer-based models. Whilst the use of such techniques will provide many advantages for coal companies, particularly in terms of efficient utilisation of their human resources, it is equally important for the decision makers to have an awareness of the limitations inherent in each particular computer-based model being used to provide information for the decision making process. A recommended procedure for identifying such limitations - by analysing the 3 major elements of the model - is presented. The human aspects of increased use of computer-based techniques are emphasised throughout the paper.

Jan 1, 1983

By D. A. Dukelow, G. Derge

THE Fe0-Mn0-Si0, system has many properties of fundamental interest besides its occurrence in steel-making. The system is the simplest ternary complication of the FeO-SiO, binary whose electrochemical properties have been explored. Therefore, knowledge of the conformance of Fe0-MnO-SiO, melts to Faraday&apos;s laws, as investigated by current efficiency measurements, would be of particular value in interpreting the observed variations of electrical conductivity, while at the same time furthering understanding of this type of molten oxides. Pertinent to the present study are conductivity data of FeO-SiO, and Fe0-Mn0-SiO2, and current efficiency data of FeO-SiO,. Concerning conductivity measurements, Inouye, Tomlinson, and chipman&apos; studied the specific conductivity, a, of molten wüstite as a function of temperature and oxide addition. Liquid FeO in equilibrium with an iron crucible was found to have a o whose magnitude and positive temperature coefficient were undeniably semiconductor in nature (o1400°C = 269 ohm-1cm-&apos;). Additions at 1400°C of 5 mole pct MnO decreased o to 227 while a similar addition of SiO2, dropped o to 125. Additional SiO2 produced an exponential decline of o. It was reasoned that because wüstite is known to be oxygen excess and since there is no pronounced change in oFeO upon melting, that UFeO(L)is p-type semiconduction. Björling2 gives o data for the ternary FeO-MnO-SiO, using fayalite, 2 FeO-SiO,, as the base substance. Upon addition of tephroite, 2 MnO-SiO, he noted a small decrease in o. Taking his data for 1400°C with one-half of the fayalite replaced by tephroite, o shows a decrease of some 40 pct relative to o for fayalite, i.e., 5 ohm-&apos; cm-&apos; to 3. In line with this observation, Mori and Matsushita3 reported that substituting MnO for FeO in the silicate de- creased o slightly except at high SiO, contents where the decrease was somewhat larger. Investigating the ionic nature of FeO-SiO2 melts, Simnad, Derge, and George4, found the anode current efficiency, C,, as calculated from iron anode weight loss, was temperature invariant and in general increased with SiO2 concentration. The authors suggested the possible presence of electronic conduction to explain why C+ < 100 pct. Fig. 4 includes their results as curve (b). EXPERIMENTAL METHOD Apparatus—Fig. 1 is a schematic section of the electrolysis cell used in all the current efficiency runs. The melt was contained in an iron crucible that rested on an alundum ring. A centered silica tube came within 1 in. of the surface of the melt and initially served as a thermocouple well and then as the guide for the anode.

Jan 1, 1961

By R. R. Hawkins

PEoperly designed tubing strings make it possible to continue the flowing life of wells beyond the stage where ordinarily they would be put to pumping. Wells no longer able to flow through 2-in. tubing can be made to produce through smaller tubing if conditions within the well are carefully studied and correctly designed strings are installed. In this way, pumping expense may be postponed and in some pools it is within reason that the entire recovery may be obtained by natural flow if maintenance of pressure is practiced. Infrequent tubing changes would be necessary but their cost would be much less than that of installing and maintaining pumping equipment. If small wells are to be made to flow naturally, careful consideration must be given the actual lifting mechanics within the string, so that fairly accurate knowledge of reservoir conditions, especially pressure, is essential. Wells producing between 5 and 25 bbl. daily are classified here as "small wells." Exponential Flow A maximum of the energy contained in the expanding gas must be employed to do useful work if natural flow is to be continued. It is evident that adiabatic expansion would defeat this purpose, therefore the velocity of the gas must be held down to a minimum in order that isothermal expansion may be approached. Of course, true isothermal expansion would not be obtainable in an oil well, hence the use of the term "exponential." 1 Obviously the closer the approach to isothermal expansion, the more efficient the lift. Experiments by the U. 8. Bureau of Mines² have shown that for isothermal expansion to take place in a gas well where water is being produced, a definite relationship exists between the depth of the well and the minimum operating pressure. The latter must be such that the tubing fill-up, if static conditions prevailed, would be equivalent to 14 per cent of the distance between the top of the fluid inside the tubing and the tubing head. It has been observed that variations in this essential ratio

Jan 1, 1932

By W. N. Page

Among engineers engaged in mining coal for river transportation, probably no other subject of equal importance has received so little attention as the methods of transferring into barges and other craft. The liability of all our streams to sodden freshets and their attendant drift and ice-gorges, seems to have had little effect upon the design and construction of what are commonly known as rivertipples, beyond the building of breakwaters, and other similar devices, to guard expensive structures from damage. The first method adopted for such transfer was a simple incline, with a movable cradle, which could be raised or lowered to suit the different stages of water. This system, though limited to a small capacity, and to cars not larger than those commonly used underground, possessed two advantages. The first cost was comparatively small; and, since the structure did not obstruct the channel, there was little risk from freshets, the utmost damage from which could be repaired at small expense. Its disadvantages, however, were many, the principal among them being the breakage of the coal by reason of the necessarily high dump; the damage to barges from the same cause; and the difficulties of screening and distributing the different sizes into separate barges. That system has been almost wholly abandoned of late, in favor of the basket-arrangement, lowering vertically into the barge, with the aid of counter-weights, which return the empty basket; while pipes or chutes convey the small coals into other barges, from a complete set of screens, which this method will readily accommodate. As far as my observations have gone, the latter system is now universally employed along all the tributaries of the Ohio. It

Jan 1, 1889