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By Jay A. Carpenter

WAR?S impact on Nevada mining and rnetallugrcal operations has brought about a rapid rise in the gross value of the ores mined and milled for the atratezic metals, and a sharp decrease in that for the precious metals. The State?s total production over the present war years will averaged out 10 per cent above the good record of $39,000,000 in 1937. However. this annual production is low in contract to that of nearly $47,000,000 in 1877 in the days of the great bonanza on the Comstock, and that of nearly $49,000.000 in 1918 during the last World War..

Jan 1, 1944

By H. S. Gibson

A PROCESS that has come to be known locally as "multistage stabiliza-tion" has been developed in the Haft Kel field of the Anglo-Iranian Oil Co. in southwest Iran, for the recovery of casinghead gasoline. It con-sists in releasing the dissolved gases from the crude by stages, a practice common in many fields, but which, so far as is known, has nowhere been carried to the extent to which it is employed in Iran. It has been in use there for nearly nine years, during which time some 200 million barrels of crude have been handled by the process. This process of gasoline retention consists in preventing the greater part of the casinghead gasoline hydrocarbons (the butanes and pentanes) from ever leaving the crude, instead of allowing them to be vaporized and then recovered from the lighter gases by the usual compression or absorption processes. Its efficiency is fully equal to that obtained by the absorption process; its disadvantage is that it increases the quantities of ethane and propane in the crude sent to the refinery, but with the growing demand for propane this drawback is vanishing. When casinghead gasoline is recovered as a separate liquid in the Iranian fields, it is blended with the crude, as the only outlet is through the refinery, and the crude-oil pipe line offers the cheapest means of transportation. It is under these conditions that the retention of the butanes and pentanes in the crude by multistage stabilization is a most attractive process, possessing as it does the following advantages: (1) extreme simplicity, (2) low first cost, (3) easy installation, (4) practically 100 per cent operating-time efficiency, (5) no operators required, (6) no water or other services required, (7) negligible maintenance, (8) once established, very little routine testing is necessary. The one essential for reasonably efficient multistage stabilization is that the flowing pressures of the wells should be relatively high; i.e., they should not be less than about one-third the saturation pressure of the crude in the reservoir. This is a very general statement, of course, and much depends on the type of crude and its temperature.

Jan 1, 1939

By T. L. Joseph

A study is made of the amount of solution loss necessary to maintain the reducing power of the gas stream in the blast furnace. Curves are presented to show the effect of solution loss, moisture in the blast, and carbon dioxide from the flux on the nitrogen in the THE blast furnace process is based upon the counter flow of gases and solids. As CO, N, and H, flow upward from the combustion zones, oxygen is acquired from the descending charge. In the reduction of iron ore, a portion of CO is converted to CO, and similarly a portion of H, is converted to water vapor. The inert N,, from the air used in combustion, passes through the furnace with little change. Its concentration is, however, decreased by reactions such as direct reduction and solution loss which increase the volume of CO in the gas stream; Similarly the evolution of C02 from the limestone also dilutes the nitrogen. he purpose of this paper is to illustrate an idealized and simplified method of studying furnace processes by following changes in the gas phase between the tuyeres and the stock line. A more specific objective is to evaluate the effect of solution loss upon the CO/CO, ratio in that region of the furnace in which FeO is reduced to metallic iron. This last stage of reduction requires relatively high CO/CO, ratios to exceed the equilibrium requirements. Solution loss or the reaction of COZ with C to produce CO has a pronounced effect upon the ratio of the carbon gases and is necessary to maintain the reducing power of the gas stream if the consumption of coke is low. It will be explained later that indirect reduction followed by solution loss is stoichiometri-cally equivalent to direct reduction. Calculations will be made to show how the composition of the gas in the region of the mantle varies with coke consumption and with different amounts of solution loss. Such calculations show the condi- tions under which gasification of C with oxygen in the charge is needed to maintain the reducing power of the gas. Equilibrium conditions for FeO and the carbon gases will be used to establish a minimum CO/CO, ratio below which reduction will not proceed. The manner in which carbon is gasified in the furnace, at the tuyeres with oxygen in the air or above the tuyeres with oxygen from the charge, will be a basic feature of all calculations. It is hoped that greater interest in the use of top gas as a means of following furnace reactions will be aroused by the calculations and generalized curves which are presented. Bosh Gas Equations Subject to some alteration by the amount of moisture in the blast and by direct reduction, the gas leaving the combustion zones of a blast furnace has a definite composition. Because a relatively small amount of oxygen is acquired from the charge in the bosh and in the crucible, the products of combustion undergo little change until they enter the shaft. Bosh gas is, therefore, essentially the products of combustion of carbon in a deep fuel bed with air. The relative weights and volumes of reacting materials are expressed by the equation: 2~ + 0? + 3.76N, = 2C0 $ 3.76NZ [I] Air Bosh Gas -air = 79% N? = 3.76) 21% 02 Starting with a known mass of C consumed largely by air, Eq 1, but partly by water vapor, Eq 2, the volume and C + H2O = CO $ H? [21 composition of the bosh gas can be calculated and subsequent changes followed as reactions take place at various elevations in the furnace. As shown in

Jan 1, 1952

By M. Stern, I. S. Servi, W. W. Webb

ZINC has been considered an ideal material for investigations of the behavior of dislocation walls in metals. It has appeared particularly useful for studies of the mechanisms of plastic deformation and the motion of low-angle boundaries under stress, because orientated crystals are easily grown and cleaved. Moreover, the hexagonal structure makes the introduction of controlled tilt boundaries relatively simple. Apparently, another of the many reasons for selecting zinc as a working material is its commercial availability at the 99.999' pct purity level. However, most elements are only slightly sol-

Jan 1, 1959

By Joseph A. Holmes

(Pittsburg Meeting, March, 1910.) AT the Mining Experiment Station of the U. S. Geological Survey, in Pittsburg, an investigation of the process of combustion is being carried on in a specially-designed furnace having an unusually long combustion-chamber. This work is conducted by a committee consisting of H. Kreisinger, mechanical engineer; Dr. J. C. W. Frazer, chemist; and Dr. J. K. Clement, physicist. The problem, essentially one of physical chemistry, is extremely interesting to all who are concerned in the burning of coal or the construction of furnaces. The main object of these experiments is to ascertain the relation between the amount of the volatile combustible driven from the coal and the combustion-spaces necessary to burn it completely. Our best steam-coals vary from 15 to 45 per cent. of fixed combustible. The greater part of the latter is burned on the grate; but the volatile combustible leaves the freshly-charged coal and must be burned in the combustion-space. If this space is not large enough, the volatile combustible will leave the furnace only partly burned, and the result will be a considerable heat-loss and a smoky stack. Strictly speaking, the factor which determines the completeness of combustion of the volatile matter, after it has been mixed with a certain amount of air, is the length of time the mixture is allowed to remain in the combustion-space; but this length of time depends on the extent of the space itself. Let us suppose, for instance, that, when a given coal is burned at a certain standard rate, the volume of the volatile combustible driven off per second is 10 cu. ft. Adding, say, 10 cu. ft. of air, the volume of the resulting burning mixture is increased to 20 cu. ft. If the combustion-space is 20 cu. ft., the burning mixture will stay in it,

May 1, 1910

By Edwin Dudley Martin

DURING the past twelve years the iron and steel industry has made a major advance through the development of the continuous wide strip rolling mill. So far-reaching have been the results that not only has a better product been sold at a lower price but this improvement in quality has permitted manufacturers of products using steel to make important savings in the cost of fabrication. The net result has been a better product at lower cost to the consumer without reduction in either employment or of wages paid within the industry. That is why the iron and steel industry is proud of its attainment. Being a basic industry of strategic importance, such an advance in technology has had its effects on our internal economy, our standard of living, and our industrial power as a nation in both peace and wartime.

Jan 1, 1939

By Robert S. Williams

On several occasions, when 60-40 brass is first obtained in the beta condition by quenching at about 825" C. and is then reheated, the writers have noticed that reerystallization will take place in the form of twin crystals at the grain boundaries of the original beta crystals. It was, therefore, thought that interesting results would be obtained if this twinning process was studied further, especially as to the temperature at which it first occurs. The material used in the investigation was a bar of extruded muntz metal, 1/2 in. in diameter, and of the following composition: Copper, 60.21 per cent.; zinc, 39.73 per cent.; lead, trace; iron, trace; tin, nil. Specimens 1 in. in length were sawed from this bar and a hole was drilled into the side of each specimen until it reached the center, and the tip of a platinum-platinum rhodium thermocouple was inserted. A small Hoskins' resistance-type electric furnace was used for heating the specimens. The specimens were first heated at 840' C. for 2 hr. and then quenched ' in cold water, in order to get the material entirely in the beta state. In every case, in the reheating process, the furnace was brought to the desired temperature before the specimen was introduced. The time occupied in preheating was from 20 to 30 min. By sawing back 1/4 in. on each side of the hole, two parts were obtained from each specimen and duplicate observations were possible. The specimens were held at the reheating temperatures for periods of 15 min., 30 min., 1, 2, and 4 hr. All specimens were etched with a freshly prepared mixture of equal volumes of concentrated NH4IOH and H2O2.

Jan 1, 1924

By D. W. Fuerstenau

On page 1243, column 1, the first line of the author's reply should read "D. W. Fuerstenau (author's reply)---," rather than D. E., as printed. In the sentence immediately preceding the first equation (page 1243, column 2)' the word "none" was omitted. The sentence should read: "However, if enough ore is put into the mill [so] that none of the energy put into the mill is wasted on metal-to-metal impact, then the product should have size modulus determined by the relation: ..."

Jan 1, 1961

By Arthur F. Colombo, David M. Hopstock

The Lake Superior region contains extensive deposits of potential iron ore in the form of fine-grained oxidized taconite. To help assure utilization of this resource in an environmentally sound manner, the U.S. Department of the Interior, Bureau of Mines, is conducting bench- and pilot-scale research using wet high-intensity magnetic (WHIM) separation. The advantages and disadvantages of WHIM separation in comparison with other feasible beneficiation methods are discussed. Pilot plant results are given for a flowsheet in which WHIM scavenging is used in conjunction with selective flocculation and flotation. A mathematical model for use in process optimization is given. Practical aspects of matrix selection and separator design for WHIM separation of fine particles are discussed.

Jan 1, 1980

||Abad, Leopoldo F, Min Engr, Div of Mines, Bureau of Science Manila, P I '23 Abadilla, Quirico A, Geol , Logo Pet Corp Box 172, Maracaibo, Venezuela '20 ||Abarquez, Ramon F, Met, Bureau of Science Manila, P I '24 ||Abbey, Robert Graham, Student, Case School of Applied Science Cleveland, Ohio '21 Abbott, A N , Mines Supt, Mazapil Copper Co, Ltd Concepcion del Oro, Zac , Mexico '23 Abbott, Clarence E , Mgr, Mines & Quarries, Tenn Coal, Iron & R R Co. 1242 Brown Marx Bldg, Birmingham, Ala '04 Abbott, Louis Benjamin, Chief Engr, Consolidation Coal Co, Elkhorn Div Jenkins, Ky '15 Abbott, Robert R , Met Engr, Peerless Motor Car Co Cleveland, Ohio '12 ||Abbott, Wells Osborn, Ray Consolidated Copper Co Hayden, Ariz '23 Abeel, George H., Jr, Cons Min Engr 4612 W 17th St, Los Angeles, Cal '18 Abel, Albert E , Asst to Pres , Valley Mould & Iron Corp Sharpsville, Pa '19 Abernathy, George Elmer, Prof of Geol & Min , Kansas State Teachers College, Pittsburg, Kan '20 Abey, Hiroshi, Min & Met Engr, Chief Engr, Takata Min Co, 2 Yeirakucho, Nichome, Kojlmachiku, Tokyo, Japan '17 ||d'Ablamg, Philip R , Millman, Old Dominion Silver-Lead Co Ellensburg, Wash '25 Aborn, R H, X-Ray Metallographic Research, Mass Inst of Tech Cambridge, Mass '19 Abouchar, Sylvain Sley, Min Engr & Geol, care of S H Sekaly, 13 Rue El Nimr.

Jan 1, 1923

By H. G. Sell, G. W. King

An investigation was made of the lensile proper-ties of recrystallized high-purity tungsten and a W-1 pel ThO2 dispersed-phase alloy over the temperature region of 800° to 2400°C. The thoria addition resulted in a modest strengthening effect over the entire temperature region. A decrease in ductility of both materials occurred above 0.5 Tm which was caused by void formation. Current theories of IT has long been recognized that a second phase of hard particles has a strengthening effect on a pure metal. At low or intermediate temperatures (<0.5 Tm), the strengthening effect is thought to arise mainly from the interaction of dislocations with dispersed particles. Above 0.5 Tm, dynamic recovery processes greatly alter the deformation mechanisms from those simply involving glide, and grain bound- strengthening by a dispersed second phase do not adequately explain the tensile results. Melallographic examination suggests that the improved strength of tire alloy results from the effect of thoria on the mierostructure. Stress-dependent thermally activated processes were found to occur high temperatures. aries may act as sources of weakness rather than strength because of grain boundary sliding. Grain boundary sliding at high temperatures has been postulated to be the primary factor giving rise to the formation of voids or cavities at grain boundaries1-3 which in turn cause premature failure and poor ductility.4 Voids, once formed, can grow by the condensation of vacancies from the equilibrium concentration&apos; or from the excess vacancies produced by the deformation.4,5 The high-temperature tensile properties of unalloyed tungsten have previously been investigated by Sikora and Ha116 and also by Taylor and Boone.7 The purpose of the present work was to investigate

Jan 1, 1965

By S. Tandanand, Powell. L. R.

The US Bureau of Mines assessed the geological effects on the ratio of maximum subsidence and extraction thickness, known as the subsidence factor, to develop a simple method for predicting the maximum subsidence. The study is restricted to the Northern Appalachian Coal Basin where data were collected from 13 coal mines. A model previously developed to relate the subsidence factor with the lithology and with the width and depth of working panels was used in the assessment. The result shows the possibility of determining maximum subsidence without resorting to a rigorous method.

Jan 1, 1985

By C. E. Birchenall

DaVIES and Richardson1 have measured composition changes for Mn1-Owith variation in the equilibrium partial pressure of oxygen at 1500°, 1575°, and 1650°C, where 6 is the deviation from the simple stoichiometric ratio. No trend in this relationship with temperature was observed, so these remarks apply to the whole temperature range. The experimental values and their spread are shown by the bounded straight-line segments in the figure. Davies and Richardson assume that the stoichiometric oxide shows Frenkel disorder, given by the equation Mn2+Mn2+ + Mn" [1] where Mn2+ is a normal lattice ion which moves into an interstitial site (Mni2+) leaving a vacancy (Mn,"). The superscript dashes indicate that there is an excess charge on the anions surrounding the vacancy. Schottky disorder, in which a perfect crystal acquires equal numbers of cation and anion (Ov") vacancies according to leads to equations of exactly the same form in the analysis below. In view of the neutron diffraction results of Roth,2 which shows extensive Frenkel disorder in Fe1-o, Eq. [I] seems more appropriate. The deviations from stoichiometric composition, MnO, result from the addition of oxygen according to In effect Davies and Richardson ignore the variation of Mn3+in constructing equilibrium constants. This approximation might not appear to be very serious if the excess positive charges are really free posi- tive holes (P+) and if the intrinsic conductivity is high as a result of the reaction where e- is a conducting electron. However, the calculations of Buessem and Butler3 indicate that the partition functions of the free charges make a large contribution to the equilibrium constant, and this approximation would not be a desirable one. Furthermore, Morin4 shows that the positive holes are probably localized in MnO and therefore are described better by the mass action principle than by a degenerate gas model. Davies and Richardson&apos;s considerations require that activity corrections be applied beyond a 6 value of about 0.005. It is proposed to show here that the dissociation pressure curve can be calculated reasonably well over the whole composition range studied without activity corrections by choosing appropriate equilibrium constants for reactions 1 and 2. As stoichiometric composition The mass action constant, Ks, for reaction [I.] and the equilibrium constant, K,, for reaction [2] are given by where the concentrations which do not change significantly have been absorbed into the constants. The brackets denote concentrations. The deviation from stoichometric composition is given by gardless of [Mni2 ]. Substituting Eq. [7] in [6]

Jan 1, 1961

By H. K. Birnbaum

The termination of a twin lamella in the interior of a crystal requires accommodation of the strains at the tip of the twin which result from coherency of the twin and matrix. In zinc and magnesium crystals,

Jan 1, 1960

By E. C. W. Perryman

The recovery of X-ray line broadening, hardness, and electrical resistivity from cold worked AI-Mg alloys has been investigated. The results, together with those from density measurements, suggest that magnesium atoms freeze in the excess vacancies formed by cold working, and that this affects the climb of dislocations during the recovery process. PREVIOUS work1, " has shown that while 1 pct Mg increases the activation energy for recrystalliza-tion, it decreases the activation energy for the recovery of mechanical properties and decreases the subgrain size both after cold working and annealing. A similar result has been reported by Varley2 for an A1-2 pct Mg alloy. With plastic deformation at high temperatures, McLean and Farmer&apos; and Rachinger have found that magnesium appears to retard the motion of dislocations and, furthermore, they find little or no effect of magnesium on the size of subgrains formed during high temperature deformation. In view of the apparent contradictions as to the effect of magnesium on subgrain size, the recovery process in Al-Mg alloys has been investigated more thoroughly by studying the annealing out of X-ray line broadening, hardness, and electrical resistivity from alloys cold worked at room temperature. Material Used—The chemical analyses of the alloys are given in Table I. Fabrication—The material used was cold rolled 20 pct at room temperature, the grain size prior to the last cold rolling operation being similar to that used in previous work; i.e., 230. The experimental procedure for annealing, determination of X-rav half-veak breadth. hardness measurement, electEica1 resistivity, and density and metallographic examination was exactly the same as previously described." Variation of X-Ray Half-Peak Breadth with Annealing Time—Isothermal annealing curves at 100°, 200°, and 250°C were obtained for material cold worked 20 pct. The half-peak breadth of the (333) Ka, line directly after cold working is shown as a function of magnesium content in Fig. 1. Only with the 2.87 pct Mg alloy was overlapping of the a, and n.. reflections observed to any appreciable extent. To separate these, Rachinger&apos;s method&apos; was used. Typical isothermal annealing curves are shown in Figs. 2 and 3 for 100" and 200°C, respectively. These curves are similar to those obtained previously for super-purity aluminum except that the

Jan 1, 1957

By E. W. Shaw

Continued discussion of the paper of Roswell H. JOHNSON, presented at the New York meeting, February, 1915, and printed in Bulletin No. 98, February, 1915, pp. 221 to 226. See also Bulletin No. 101, May, 1915, pp. 1157 to 1162. E. W. SHAW, Washington, D. C. (communication to the Secretary+). -With the word petrology-literally the science of rocks-being used primarily for igneous rocks, and with geophysics coming to mean the study of lavas and the rocks into which they solidify, contributions to the knowledge of the physical chemistry of sedimentary rocks, even though only ideas which may be used as working hypotheses, become most welcome. The forces which control the formation and subsequent history of the stratified portions of the earth&apos;s crust are so little known that no one has yet been able to settle finally the questions as to whether petroleum is of organic or inorganic origin; whether it originated far from its present position, or nearby. Yet both the chemical and physical problems of the rocks in which oil occurs seem to be more simple than those of the igneous rocks. The oil-bearing rocks of western Pennsylvania, for example, have in all probability never been subjected to a pressure exceeding 3,000 or 4,000 lb. to the square inch, nor to a temperature higher than 100° or 200° C. These pressures are considerably below the crushing strength of rocks, and the temperature far below their melting point. The igneous rocks,, on the other hand, have been affected by enormous pressures and very high temperatures and yet steady progress is being made in reproducing in the laboratory the conditions of their formation and subsequent modification within the earth. The solution of the sedimentary-rock problems would seem to be fully as important as those of igneous rocks, and yet we must content ourselves with reasoning backward and our inferences as to what has happened are oftentimes little more than guesses.1 One of the fundamental problems is the origin of the salt water in oil fields. Is the salt water fossil sea water; has it been formed by the solution o-f salts of various kinds from distinct beds, from disseminated par-ticles, and from the weathering of suitable grains in the rock; or is it of deep-seated origin? Its general resemblance to sea water points to the first, but the principles held by some concerning the free circulation of water throughout the earth&apos;s crust, and certain peculiarities of composition indicated by the few analyses available, seem out of harmony with such an explanation.

Jan 7, 1915

By George K. Burgess, Robert A. Hadfield

1. Introduction.—The methods of production of sound steel ingots have been described in several papers read recently before this Institute. It was thought by Director Stratton, of the U. S. Bureau of Standards, and ourselves to be of sufficient interest and importance, as a further contribution to this subject, to compare the properties of rails rolled in one mill according to American practice, from several types of ingot of substantially the same chemical composition but cast by several processes; and to compare in considerable detail the properties of an ingot manufactured by the Hadfield special-feeding process and one of the usual type for rolling into rails. We are greatly indebted to F. W. Wood, President of the Maryland Steel CO., who made this investigation possible by kindly placing his rail mill at our disposal; and he and his associates at Sparrows Point did everything possible to make the experiment a success, including the execution of several of the tests and analyses. 2. Classification and Manufacture of Ingots.—Of the ingots used in this investigation, eight were made in Sheffield and furnished by Sir Robert Hadfield, and one was made and furnished by an American steel company,l as a comparison ingot, and was supposed to represent the usual type of ingot from which rails are made. The characteristics of the ingots are given in Table I. Ingots 1, 2, 3, and 4 were cast large end up and fed by the Hadfield method in the usual manner with charcoal and blast continued until the molten steel has set on the top of the head, say varying from 20 to 40 min. To ingots 1, 2, and 4 was added 0.1 per cent. aluminum, and to the nickel-chrome ingot, No. 3, 0.125 per cent. For sake of comparison, there were also included two ingots, Nos. 8 and 9, cast with the small end up and fed by

Jan 1, 1915

By G. B. Misra

While investigating on the aerodynamic resistance of airways supported with peripheral timber sets, at regular intervals, the following theoretical equations were developed by the author to estimate the resistance coefficient of such airways: [ ] for S < 1, where f is Darcy-Weisbach resistance coefficient of the airway, C is modified drag coefficient of the supporting member, D is equivalent diameter of the bare airway, 8 is ratio of the approach velocity over the sets to the average velocity of the bare airway, A is cross-sectional area of the bare airway, a is projected frontal area of the sets, A., is cross-sectional area of the air stream at the vena contracta inside the set, S is spacing of the sets, f, is resistance coefficient of the bare airway, l is length of aerodynamic influence of sets, p is perimeter of the bare airway, p, is setted portion of the perimeter of the bare airway, pe is unsetted portion of the perimeter of the bare airway, and P shielding factor. The equations were verified experimentally in a model rectangular airway supported with one- (bars), three-, and four-piece sets of square-section timber of three different sizes and were found to hold true. The work has been further extended to one-, three-, and four-piece sets of round timber of 2.6, 3.2, and 3.8 cm diam with the same experimental set up. Tests have been carried out for spacings of 25, 50, 75, 100, 150, and 200 cm over a regime of flow defined by the Reynolds number (with respect to the equivalent diameter of the bare duct) ranging from about 1.5 X 106 to 5 X 106 using the same experimental techniques. The values of f are calculated in the manner indicated in [Ref. 1]. Unlike with square-section timber, the resistance coefficient f of the airway setted with round timber shows a distinct variation with the Reynolds number of flow. This conforms to observations made by Sales and Hinsley.2 In order to have a comparable value of f for all types of sets with all sizes of timber, it was necessary to select the value of f at a fixed Reynolds number of flow. Since f is chiefly a function of the drag coefficient of the sets, the appropriate Reynolds number RE is that with respect to the diameter of timber in the set. Considering the diameters of timber used and the regime of flow over which measurements were made, f was chosen at a value of RE = 20,000 in all cases. The f vs. S curves are maximal in nature and in conformity with theory, the f vs. 1/S curves are straight lines up to a value of S = 1 beyond which they show a distinct flexure. The observed values of 1, the length of aerodynamic influence of sets, agree with the relation 1 = 42 e, developed for square-section timber sets, thus suggesting that the shape of timber has little influence on the length of aerodynamic influence. The value of the modified drag coefficient CD for round timber was calculated in the same way as for square timber in Ref. 1, taking the contraction factor Z = 1.5 for round-edged constrictions. CD has an average value of 0.96 with a standard deviation of 6.08% as compared to the free stream drag coefficient of 1.2 at RE = 20,000 for long cylindrical obstructions The shielding factor [ ] is plotted against S/1 in [Fig. 1]. The curves are more or less independent of the size of timber, but are different for the different types of sets, possibly due to their different degree of symmetry. Values of f calculated by the author&apos;s [Eqs. 1 and 2], using experimental values of CD&apos; and [ ] and taking I = 42 e, are plotted in [Fig. 2] against experimentally measured values of f for different types of sets with different sizes of round timber. The values agree closely with a standard deviation of only 5%, thus establishing the veracity of the theoretical equations developed by the author for round timber as well. A comparison was made between the Xenofontowa4 equations (the only other reasonable relations available for the estimation of the resistance coefficient of supported airways) and the author&apos;s [Eqs. 1 and 2] by comparing in [Fig. 3] the values of the resistance coefficient f computed by the Xenofontowa relations with those experimentally measured by the author. In order to make

Jan 1, 1975

By Orson Cutler Shepard, Charles F. Skinner

THE leaching method that was first widely used with the cyanide process consisted of percolation leaching of crushed ore in vats or leaching tanks. It was frequently necessary to separate the sand for cyanide treatment and discard the slimes, because only granular material allows the necessary amount of solution to percolate through it in a reasonable time. Later a slime process consisting of agitation followed by thickening and filtration was developed, and is extensively used to the present day. Even though the agitation-leaching slime process is considered satisfactory, the cost of plant and of operation are both greater than for a percolation-leaching plant of equal capacity. This situation has been recognized in the hydrometallurgical treatment of copper-bearing slimes; and a considerable amount of work has been done at the Southwest Experiment Station of the U. S. Bureau of Mines in an effort to develop a percolation method of treating slimes. Experimental work on the copper-leaching problem was started by H. E. Keyes1, and later tests were made by J. D. Sullivan and A. P. Towne2. The Bureau of Mines work resulted in the development of a process by which slimes were moisture-agglomerated with sand and crushed ore, to form a permeable mass through which solution could be trickled without breaking down the glomerules. The agglomeration trickle-leaching method was developed on a small scale and finally tried out in a 12-ton vat. Successful results were obtained as long as the leach solution was added slowly, so that the agglomerated charge was never flooded. If the leach solution flooded the charge, the glomerules broke down and the charge became impervious. There are two important difficulties in the application of the agglomeration trickle-leaching method to the cyanide process for gold and silver ores:

Jan 1, 1937

By Paul H. Lu

This paper proposes an unconventional, simple, and practical method of measuring mining-induced ground stresses with hydraulic borehole pressure cells. The method is a direct ground stress measuring technique. It does not require the value of deformation modulus for back-calculation of stresses; instead, it directly measures the ground stress in situ. The applicability and practicality of the technique are shown by two case studies. The technique may be applied to monitoring a stress buildup that may lead to mine roof failure or to rock and coal outbursts.

Jan 1, 1984