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By E. J. MCOAUSTLAND

THE behavior of steel after overstrain and at moderate temperatures is fairly well known. It has been made the subject of much investigation, and our knowledge is clear and definite on many points. The ultimate raising of the elastic limit, after moderate overstrain, and the consequent lowering of the ductility, seem to be well established. It is also well understood that the immediate effect of overstrain is to lower the elastic limit, possibly to zero, but that if not interfered with, this limit will subsequently rise higher than before. The "tests after moderate temperature," reported in this paper, were undertaken to verify the above statements for the particular steel under investigation, and also to determine, if possible, the total time required for complete recovery from this state of overstrain. The behavior of overstrained steel at temperatures at or below 32° F. is not so well known. Tests made by Prof E. G. Coker, at McGill University,' show that steel, overstrained and subjected to cold, will remain in a state of overstrain for an indefinite period. I am not aware of any other published results of tests along this particular line. The effect of time and temperature on the recovery of steel from overstrain was made in 1902-3 the subject of sortie investigation in the laboratories of the College of Civil Engineering of Cornell University. A general plan was outlined in connection with the regular courses of instruction in testing of materials; but the press of routine work and the demands of the schedules on the time of the students were so great as to presage long delay in the completion of the work. Not much had been accomplished up to 1904-05, when Messrs. E. C.

May 1, 1906

By F. J. Longworth

For a number of years an intensive study has been made to improve the blast-furnace practice at Copperhill not only as to costs but to provide a good grade of gas for the acid plants. This study, took us back to the fundamentals of successful pyrite smelting; namely, a blast furnace working on a clean sulfide ore, free from fines, and the use of quartz high in silica as a flux. In 1919, the quality of the flux was improved and its effect on the metallurgy was very marked. To improve the practice further, it was necessary to work out some method of treatment for the sulfide fines and the siliceous and refractory ores, other than in the blast furnace. A series of milling tests indicated that these products could be successfully treated by differential flotation, and in 1922 plans were made and a flotation plant built. It was estimated that the flotation plant would deliver to the smelter 40 to 50 tons of concentrates per day; the problem was what to do with these concentrates. It was out of the question to attempt to smelt them in a blast furnace because of the dust losses and, because our practice demands a charge free from fines for satisfactory operation. There is no custom smelter in the vicinity to which concentrates may be sold, pending the time when the tonnage will be sufficient to warrant roasters and a reverbatory furnace. Sintering and nodulizing were investigated but neither method fitted into our scheme of metallurgy. A close study of the converter practice was then made to see if some method could not be evolved to smelt this tonnage of concentrates in a converter without preliminary treatment. At that time, the converter installation consisted of two 12-ft. Great Falls converters, which were handling 12 to 14 per cent. matte. The heat balance of the converters working with 12 to 14 per cent. matte was more than sufficient to smelt the contemplated tonnage of concentrates but the mechanical difficulties. of feeding fines into the Great Falls converter made the use of this type of converter impractical.

Jan 9, 1924

By Walter Weeks

THE process of cooling air by allowing it to expand and do work in an engine is well known, but the theory of obtaining cold air by free expansion without the aid of an engine operating with cutoff has been little discussed. CASE I If compressed air is allowed to expand to the atmospheric pressure through an orifice in an air line that is supplied by a running compressor, no cooling results except the negligible one due to the Joule-Thompson effect, which will not be considered in this discussion. The effect of moisture will also be neglected.

Jan 1, 1937

By J. H. Wernick

IN temperature-gradient zone-melting1 a molten zone is moved through a solid or across a solid surface by the establishment of a temperature gradient. This technique has both practical and fundamental aspects. One practical application is to make p-n junctions for semiconductive devices, particularly for devices in which the junctions are desired within the semiconductor. From a fundamental point of view, the technique is being investigated as a method for determining diffusivities in liquid alloys, and preliminary diffusivity results have been reported by the writer." In this paper, the effects of crystal orientation, temperature, and molten zone thickness in temperature-gradient zone-melting, and the bearing of these effects on diffusivity measurements and n-p-n junction formation are discussed. Experimental Procedure An effect of crystal orientation was noted in early experiments. To facilitate its study, movements of wire zones across a surface, rather than through the body of a single crystal, were observed for various surface planes and travel directions. The experirr-entai setup is illustrated in Fig. 1. The graphite end-section for the high temperature heater has an apron about 1/16 in. above the upper surface of the crystal. This apron insures that the surface temperature of the block is equal to or greater than the temperature within the block at every point, Thus, the zone does not penetrate the block and convection in the liquid is minimized. The experi-through a block is shown in Fig. 2,

Jan 1, 1958

By W. L. Grose, J. E. Nealy

A device developed by the U.S. Bureau of Mines for the detection and quenching of coal mine explosions suffers from the inability to discriminate between the light emitted from hydrocarbon combustion and that emitted by electrical sparks and miner's cap lamps1. Since the quenchant device is activated by an internal explosive charge, the possibility of serious injury to nearby personnel demands a detector which can reject false signals. Described herein is a detector which can provide a rapid response signal upon the emission of radiation from hydrocarbon combustion and concurrently reject spurious signals from such sources as sparks and cap lamps. It was suggested that a detector might be developed to operate on the principle of monitoring the radiation intensity emitted from two separate spectral regions and ratioing the intensities2. A series of experiments was conducted for combustion of methane-air mixtures which demonstrate the ability of such a detector to discriminate between combustion and spurious signals. Experimental Apparatus A cylindrical (3.8 in. diam by 12 in.) stainless-steel shock tube test section was used as a combustion chamber. The test section was equipped with quartz windows (2 in. diam) on either side, a piezoelectric pressure transducer, and two steel electrodes. A 10-kv capacitor discharged across the electrodes provided a submicrosecond duration spark to ignite the gas mixture within. The desired partial pressures of methane and air were obtained by using a Wallace and Tiernan 0-800 mm Hg pressure gauge with which pressures could be determined to an accuracy of % mm Hg. All tests were conducted with a total pressure of 1 atm in the chamber. To

Jan 1, 1972

By P. A. Toynbee

An experimental air-slide classifier1 has been applied to the de-dusting of ground dolomite in an attempt to produce a grade of -30 +150 mesh (B. S. Sieves) material from a raw material containing 30-35% of the -150 mesh fraction. Air flows varying between 1.5 and 2.5 cu ft/sec sq ft of screen area were used. The throughput of dolomite was between 80 and 100 lbs/h. inch of screen width. The size analyses of the de-dusted material and of the original dolomite are shown in table at right. The proportions of the +100 mesh material in the feed and in the de-dusted products have been used to calculate materials balances, on the assumption that there is no loss, as dust, of this +100 mesh fraction. By interpolation, it can be shown that a de-dusted product recovery of 68.5% will be obtained at an air flow of 2.13 cu ft/sec sq ft of screen area. The feed material contains 68.5% of +150 mesh material, so that if the de-dusting gave a perfectly sharp cut, the product would contain no material less than 150 mesh. Further calculations based on the size analyses, show that, at an air flow of 2.13 cu ft/sec sq ft of screen air, the -150 mesh fraction in the de-dusted product will fall just below the specified maximum limit of 5%.

Jan 1, 1964

By F. J. Longworth

FoR a number of years an intensive study has been made to improve the blast-furnace practice at Copperhill not only as to cost% but to provide a good grade of gas for the acid plants. This study took us back to the fundamentals of successful pyrite smelting; namely, a blast furnace working on a clean sulfide ore, free from fines, and the use of quartz high in silica as a flux. In 1919, the quality of the flux was improved and its effect on the metallurgy was very marked. To improve the practice further, it was necessary to work out some method of treatment for the sulfide fines and the siliceous and refractory ores, other than in the blast furnace. A series of milling tests indicated that these products could be successfully treated by differential flotation, and in 1922 plans were made and a flotation plant built. It was estimated that the flotation plant would deliver to the smelter 40 to 50 tons of concentrates per day; the problem was what to do with these concentrates. It was out of the question to attempt to smelt them in a blast furnace because of the dust losses and because our practice demands a charge free from fines for satisfactory operation. There is no custom smelter in the vicinity to which concentrates may be sold, pending the time when the tonnage will be sufficient to warrant roasters and a reverbatory furnace. Sintering and nodulizing were investigated but neither method fitted into our scheme of metallurgy. A close study of the converter practice was then made to see if some method could not be evolved to smelt this tonnage of concentrates in a converter without preliminary treatment. At that time, the converter installation consisted of two 12-ft. Great Falls converters, which were handling 12 to 14 per cent. matte. The heat balance of the converters working with 12 to 14 per cent. matte was more than sufficient to smelt the contemplated tonnage of concentrates but the mechanical difficulties of feeding fines into the Great Falls converter made the use of this type of converter impractical. While there was no opportunity to experiment with the Pierce-Smith converter, equipped with a Garr gun, theoretically it seemed practical

Jan 1, 1925

By W. S. Weeks

In coursing the ventilating air through a mine it is often necessary to restrict a comparatively open split in order that it may carry exactly the desired quantity of air. Such a restriction is known as a regulator, and usually takes the form of a partition with a hole in it. The quantity of air circulating is controlled by the size of the hole or orifice. For example, it is desired to force a quantity q I cu. ft, per min. through split a (Fig. 1) and the quantity q2 through split b. It requires a pressure of 2 in. water to force the desired quantity through a, and a pressure of 1 in. to force the desired amount through b. The pressure drop between points A and B must be 2 in and a pressure of 1 in. must be destroyed in split b. This is done by inserting a regulator in b, which causes the velocity to increase in the orifice and results in a change from pressure-head to velocity-head. If the air, after passing the orifice, is slowed down in a turbulent manner, all of the velocity-head does not change back into pressure-head, so a permanent loss of static pressure results. A classic formula for computing the area of an orifice to destroy a certain amount of static pressure has been handed down from early days: 0.0004Q a =2 This formula is based on the assumption that all velocity-head in the orifice is "destroyed;" that is, does not reappear again as either velocity-pressure or static pressure. The derivation of the formula is as follows: h = head lost in regulator in fect of air. v = velocity in regulator in fect per second. q = quantity circulating in cubic feet per second. Q = quantity circulating in cubic feet pcr minute. a = area of orifice in square feet.

Jan 1, 1928

By George C. Bateman

I HAVE been introduced in the dual capacity of president of the Canadian Institute and Metals Controller for Canada. There are three particular points of similarity between these two positions. They are both temporary ; they both have to do with the mining industry ; and by a peculiar coincidence they both pay me exactly the same salary. It is difficult to appreciate the background of our present situation without knowing the really tremendous changes that have taken place since the last war. I sometimes think that even among ourselves we are likely to forget the extent to which our great mining industry has been expanded. In 1914 Canada's gold production amounted to only $16,000,000 and the suggestion was seriously ad¬vanced in Ottawa that the gold mines should be allowed to close down so that their men might be used in more important work. Today with a production at the rate of over $200,000,000 a year no one in Canada would venture such a suggestion because the output of our gold mines is the greatest single factor in producing dollar exchange, badly needed for the purchase of munitions and to maintain Canada's unbroken record of always meeting its obligations. Even with the severe restrictions now in effect against the importation of nonessentials, our imports for war purposes from the United States are resulting in the biggest adverse trade balance in our history. With us, gold mining ranks as an essential industry.

Jan 1, 1941

By R. Dawson Hall

LONG regarded as nearly worked out, the anthracite region still shows promise of a hundred years of life, for means are being found to get bottom, top, pillar, and other coal that earlier generations disregarded as too expensive to mine. Rock drivages and, still more, machinery are making it possible to get such coal. Mechanical methods enable the owner of thin beds to mine these with profit, and the miner recognizes that he must permit the use of machinery or the inexorable laws of economics will deny him opportunity to work. E. L. Dana, Jr., well outlines this situation, which in the past year became definitely established. Stripping also is recovering, safely and inexpensively, coal that past generations regarded as too hazardous and costly for mining.

Jan 1, 1935

By L. S. Pratt

IN 1910 the author was engaged in a qualitative study of the radio-activity of several chemical substances and a few minerals. In the course of the work he studied the mineral allanite (obtained from granite ledges at Topsham, Maine), and found it to be appreciably radio-active. Recently the fact was brought to his attention that the radio-activity of allanite is not well known, although Hon. R. J. Strutt in 1905 published a list of radio-active minerals with their analyses, including allanite from Amherst County, Virginia. In the work done, a standard ,type of electroscope was used, and the readings were made with a telescope, fitted with a scale, by means of which the rate of discharge could be readily determined. The natural "leak" of the instrument was carefully determined, and all results corrected accordingly. The method of study was as follows: The material to be tested was finely powdered, and spread over the bottom of a small, inactive pan. The electroscope was then charged, and the pan placed in position. The door of the instrument was closed, and the rate. of discharge carefully determined. All results were reduced to common form to permit of comparison. It is to be noted that the materials tested were not used in strictly comparable quantities, such as if 1 g. of. each had been used, but about the same quantity of powder was used (in the cases of the solid substances), so that the results are qualitatively accurate.

Jan 5, 1916

By T. G. R. Rawlins, L. E. Brosselard

Direct platinum carbon replicas have been used to study substrates prior to growth and after initial nu-cleation of the layer. Replicas have been directly stripped and correlations have been made with other replica techniques. Mechanically polished substrates are very flat with occasional areas of "dirt", which is apparently silicon. When such substrates are etched in hydrochloric acid gas, scratches and hexagonal defects (thought to be polishing compound) are revealed, together with areas of apparent redeposition. Chemically polished substrates are much less flat although much more homogeneous in appearance. Heat treat)nents have no effect. Nuclei deposited on these surfaces, using a normal silicon tetrachloride system, have been examined. Nuclei on mechanically polished subsrates occur in random areas only, whereas on chemically polished surfaces they are more uniformly distributed. THE interest in the study of thin films and now their rapidly expanding use in many fields has increased over a period of years. Much of this current interest, particularly in the field of single-crystal or epitaxial thin films, has derived its stimulus not only from possibilities for application but also from fundamental electron-microscope studies which have indicated the manner of growth of such layers from the initial nuclei.1-5 Previous work involving study of growth processes may be divided into three categories. First, vacuum deposition, primarily of metals, on a variety of substrates has been studied by electron microscopy and electron-diffraction techniques. These have shown the three-dimensional aspect of nucleation and the remarkable liquidlike behavior of the growing nuclei which coalesce to form a complete layer. More recently this work has been expanded in two ways: by growth inside the electron microscope this has obvious advantages for kinetic studies; and by growth in ultrahigh vacuum—much of this work has been done on semiconductors.8-11 It is of interest to note that metals, specifically gold deposited on rock salt, will form only polycrystalline layers in ultrahigh vacuum unless the substrate surface is contaminated.12 In general the mode of growth for vacuum-deposited semiconductor films is the same as that for metal films. The second method of growth that has been studied is that of electrodeposition.13,14 The little that has been published suggests that the mode of growth is similar to the vacuum case, except that irregularities may perturb the electric field and disturb the growth process. The third and last primary method of growing epitaxial layers is by use of chemical methods. These techniques have generated much interest and much has been published on them. Considerable electron-microscope work has been done on the defects in the layers; however comparatively little work has been undertaken on the initial nucleation and early stages of growth. Confining ourselves now exclusively to the case of silicon, Charig et a1.15 have considered the growth of silicon on silicon substrates by hydrogen reduction of trichlorosilane, and studied the films by means of replica and transmission techniques. Subsequently they have studied the same system for growth on quartz,16 and with the addition of pyrolysis of silane on quartz and alumina.17 Also Manasevit el al. have studied deposits using silane and silicon tetrachloride on sapphire.18-14 Finally, in this volume studies of deposition on beryllia and sapphire are reported. Although Revesz and Evans20 have examined complete layers, grown by means of the widely used silicon tetrachloride reaction, no detailed examination similar to that published by Charig and Joyce21 for the trichlorosilane system has been given. Therefore this investigation has examined substrate surfaces prior to growth and then nucleation on these surfaces for the silicon tetrachloride system. EXPERIMENTAL In this work the surfaces have been studied by means of standard replica techniques. Because of the very real problems associated with artifacts introduced,22 different replicas and different cleaning

Jan 1, 1967

By Larry D. Hartzog

PANELISTS Paul Chamberlin, Nerco Minerals Jim Gourdie, Goldfield Mining Corp. Roger Leonard, Cyprus Northumberland Mining Co. Eric Daniels, Tenneco Minerals John Dasher, Consulting Metallurgist Bob Shoemaker, San Francisco Mining Associates Larry Hartzog, Bechtel Civil and Minerals, Inc.

Jan 1, 1984

By AIME AIME

THE John Fritz Medal Board of Award, at its annual meeting on Jan. 21, 1921, awarded its gold medal and diploma to Sir Robert Hadfield for the invention of manganese steel. On June 1, announcement was made that the Board of Award had awarded its gold medal and diploma to Charles Prosper Eughe Schneider for "achievement in metallurgy of iron and steel; for development of ordnance, especially the 75-mm. gun, and for notable patriotic contribution ' to the winning of the war." The award to Sir Robert Hadfield is for the year 1921; the award to Mr. Schneider is for 1922. The latter was made at this time in order that the medal might be presented by the group of American engineers now visiting England and France.*

Jan 1, 1921

By P. E. Schauer

During the initial nine-year deple-tion of the McKamie-Patton pool gas-condensate reservoir, the pressure behavior and fluid analyses indicated pressure maintenance by gas injection would be attractive relative to continued pressure depletion. As a result, a gas cycling program was inaugurated in Aug., 1949, which has since maintained reservoir pressure. In order to evaluate the benefits of this program, the recoveries for natural depletion and for cycling followed by blowdown were determined by calculating the fractional balance of the molar quantities of vapor and liquid remaining in the reservoir and produced at the surface for various stages of depletion. The results of the investigation show theoretical ultimate recovery due to the cycling program will be 42 per cent greater than would be realized under pressure depletion type operation. INTRODUCTION The benefits of gas injection pressure maintenance programs in condensate reservoirs have been recognized and qualitatively described in several papers1-8 during the past 15 years. Some of these papers also describe methods for calculating the increased recovery realized from cycling; however, as a rule, hypothetical reservoirs were used as examples".'.. This paper presents an evaluation of the pressure maintenance program for the McKamie-Patton condensate reservoir and includes a description of the fractional balance method employed to determine the benefits. Reservoir Development and Characteristics The McKamie-Patton pool, Lafayette County, Ark., was opened in June, 1940, with production obtained from the oolitic Smackover lime at a depth of approximately 9,300 ft. The structure is an anticline 8 miles long by 1 to 2 miles wide, and is one of many productive Smackover structures in Southern Arkansas. Of predominant importance is the condensate-bearing gas cap portion of the reservoir, which covers approximately 4,000 acres, attains a maximum thickness of some 200 ft, and has an average thickness of 90 ft. Development of the cap was accomplished with 21 wells drilled on 160 acre spacing. An isopach map of the cap is shown in Fig. 1. In addition, an oil rim is present along most of the periphery of the pool. Production practice includes field separation of black oil, and a high pressure gathering system which carries total well stream from gas cap wells to a plant where condensate is separated and the gas is processed for recovery of natural gasoline, butane, and propane. Since the gas contains appreciable hydrogen sulfide, it is removed by amine contact, after which free sulfur is produced by the Claus process. Core analyses from 1,767 gas cap formation samples averaged 14.2 per cent porosity and 379 md dry air permeability. Connate water was restored on seven samples of gas cap rock by air-brine capillary techniques, from which the interpreted water saturation averaged 28.17 per cent. During the early life of the field, it was believed the recovery mechanism, based on several of the other regional Smackover reservoirs, might be a natural water drive. However, subsequent production and pressure history revealed that the gas cap would not be produced by water drive, but would behave as a closed reservoir. In this respect, during the nine-year period of natural depletion from initial production to Aug., 1949, the cap production of 84.3 billion

Jan 1, 1958

By Bruce Short

HIGH rock and surface temperatures combined H with small deep shafts create a difficult ventilation problem. At the Magma operation in Superior, Ariz., booster fans take air off the bottom levels, directing it first through cooling coils and then through the working places and out to the exhaust shafts. All air drawn from the intake shafts below the 3400 level is cooled before it goes to the stoping areas. Most of the ore mined at Magma has come from steep-dipping vein deposits developed for a maximum distance of 9000 ft along the strike of the vein. At present approximately one third of the tonnage is coming from a new section of the mine where the ore occurs as replacement deposits along a favorable horizon in limestone beds. The deepest mining level is now the 4800.

Jan 3, 1957

By G. E. McElroy

MUCH attention has been directed to mine-air flow in recent years, more especially in Great Britian where there is frequent reference to a theory of fluid flow developed by English engineers. Briefly stated, this theory is that for similar passages of the same relative roughness, in which fluid flow occurs, the conditions of flow are exactly the same for equal values of the product W D V, where W = density of the fluid, D = diameter of the passage through which flow occurs, V = mean velocity of flow, and m = absolute viscosity of the fluid flowing. This, the "Reynolds Criterion" of fluid flow, had its origin in the work of Prof. Osborne Reynolds' more than 40 years ago. Later, Lord Rayleigh amplified the theory2 which has been conclusively proved for small pipes by the experiments of Stanton and Pannel3 over a large flow range, and by Lacey4 over a somewhat more limited range. Concordant results on small pipes have also been obtained by numerous other investigators with single fluids over more or less limited ranges of flow. According to this theory results in one medium, such as water, are immediately applicable to another, such as air; and experimental results on models are (theoretically, at least) applicable to full-scale designs. This is of great importance in aeronautics and can be of considerable value in mine ventilation research. Hodgson, in a recent paper,5 has outlined the application of this theory to mine-air flow and recent English experiments' on the resistance of a timbered mine airway have been expressed in this form.

Jan 10, 1926

By Arthur Taggart

FLOTATION of sulphide minerals and native metals is no longer a practical difficulty. The underlying scientific principles of the method, although not explored in anything like complete detail, have been formulated with sufficient breadth so that the direction of attack on any specific case is clearly indicated. It has been known since the earliest clays of flotation that certain of the nonsulphide nonmetal minerals-e.g., sulphur and graphite-would respond to flotation by oils as sulphides do; therefore they have been grouped with sulphides in many patents. But since the development of the chemical theory of collection,1,2,3 this similarity in action has been one of the facts cited in disproof of the theory by opponents of the hypothesis.4,5,6 Air levitation? of certain oxidized minerals, both metalliferous? and nonmetalliferous, and separa-tion thereby from other oxidized minerals, is a recent development in practice, although the discovery of the method dates back 17 years.7 This paper presents evidence that the principles underlying the air levita-tion of the nonsulphide nonmetal minerals are the same as those utilized in the flotation of the sulphides and native metals. It will be apparent immediately to anyone with knowledge of mineral concentration that separation of air-levitated minerals in water from minerals not so levitated is a simple matter of water-gravity concentra-tion, the separating device employed depending solely upon the size of the particles treated and the buoyancy differences effected by the levita-tion, The usual separating means employed are: (1) a flotation machine for fine, slimy and for well aerated granular material; (2) shaking tables for granular less aerated material.

Jan 1, 1937

By T. W. Bossert

MELTING is the initial step in the fabricating of all aluminum and aluminum-alloy products. Its function may be considered as threefold: to improve the metal quality, to adjust the composition, and to change the form to that required for subsequent fabrication. Because the melting operation is generally somewhat removed from the final product fabrication, its importance is frequently overlooked. Melting equipment and melting procedures can reflect materially on fabricating procedures as well as on quality and cost of final product. The selection of equipment and the establishment and control of melting procedures, therefore, should be given careful consideration. It is the purpose of this paper to present the various factors that should be considered in establishing melting procedures and in selecting melting equipment. Certain of these are the result of the inherent characteristics of aluminum and can be treated rather specifically. Others depend on the particular production requirements and hence will have to be considered more generally. This paper is intended to cover only the melting of solids, as differentiated from fines, such as borings, turnings, and sawdust. The melting of fines, in many respects, is a subject that should be treated by itself, and practices for melting fines are by no means as standardized as are those for melting solids. The melting of fines is today the subject of considerable developmental interest; hence practices discussed today may soon be replaced by new or improved ones. CHARACTERISTICS OF THE METAL THAT AFFECT MELTING Aluminum and aluminum alloys possess several inherent characteristics that affect the melting problem. Of the physical properties, density, heat content, thermal conductivity, emissivity, and melting temperatures are important because of their effect on equipment design. A list of such properties for commercially pure aluminum is given in Table r, compared with similar properties for iron and copper. The low density of aluminum as well as of the aluminum alloys is of material advantage in the design of melting equipment, in that such equipment can be considerably lighter than similar equipment for handling the heavier metals. The density, however, particularly of the molten metal, is not greatly different from that of the oxides and other nonmetallic materials that develop or become part of the melt during the melting process. Separation of such nonmetallics is not as rapid a process as with some of the other metals, and consideration of this must be made in establishing melting procedures. Sufficient holding time to permit such materials to separate out and, in some cases, fluxing treatments to aid the separation, are required. Since some of these nonmetallics settle to the bottom of the melt, provision should also be

Jan 1, 1946

By David Burgess, Hershiel H. Hayden

Experiments at the Somerset mine, Colo., under an agreement between US. Steel Corp. and the US. Bureau of Mines are described. A test was made of the tube bundle method of mine air sampling which was developed for European longwall mines; some 300,000 running feet of tubing provided continuous monitoring at 38 locations. Carbon monoxide concentrations were obtained with standard deviations of less than 1 ppm and oxygen concentrations with standard deviations of less than 0.2%. A base level of CO index (ppm CO evolved per percent 0, removed) was determined to be zero to 20 through most of the passageways of the mine. However, in one working section where the coal was initially hot (about 180°F within a pillar) the CO index was demonstrably higher, 120 trending upward to about 60 when smoke appeared and the section was sealed. The data are discussed in terms of laboratory experiments on CO evolution from coals.

Jan 1, 1977