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By Henry M. Howe

Many direct processes have been proposed for the treatment of oxidized ores of copper by reducing the copper oxide to the metallic state, and by separating it from its impurities by a subsequent fusion. The radical objection common to all the methods which have come to my notice, except those in which sulphur plays the prominent part, is that the very deoxidizing agent which effects the reduction of the copper oxide, inevitably reduces at the same time a very considerable part, if not the whole, of the iron which almost invariably accompanies copper in its ores. The result is that, when the ore is subsequently fused, a very great quantity of the already reduced iron separates from the slag along with the copper, alloying with it, and necessitating costly subsequent operations for its separation. Thus, at Perm, in the Urals," the product of the fusion of ferrnginous copper oxides is a mixture of one hundred and fifty-tive parts of highly cupriferous pig iron with two hundred and fire parts of very impure and ferruginous black copper, containing Pome 10 per cent. of' carbon and iron, though free from sulphur, and of course very difficult to refine. If, in order to avoid this reduction of iron to the metallic state, the reducing action be made feebler, it inevitably results that a considerable part of the copper as well escapes deoxidation; and, consequently, the slags are so rich that it becomes necessary to treat them subsequently in order to recover the copper which they contain. Thus,. in treating native copper, at Lake Superior, where the reducing action is purposely made feeble in order to prevent the deoxidation of the iron, the slags from the first fusion of the ore carry so much copper as to render it imperative to treat them again, which is done in a cupola. And yet, in spite of so far weakening the reducing action as to cause a notable slagging of the copper, a very considerable reduction of iron actually takes place. These are the two dangers which threaten the smelter of oxidized copper ores. If he wishes to avoid slagging his copper, he must have so strong a deoxidizing action as to reduce a great deal of his

Jan 1, 1879

By C. M. Young

THIS is an attempt to bring together some of the knowledge of the .coal-forming conditions obtaining during the Pennsylvanian period in the Western Interior Coal Province, to sketch briefly the present extent and character of the coals produced, and to show the beginning of cor-relation of beds over wide areas. Coals of later age than the Pennsyl-vanian are not included and, for reasons that will appear later, little attempt is made to cover the districts of eastern Oklahoma and western Arkansas, and northern Texas is omitted entirely. GEOLOGICAL CONDITIONS The conditions that made possible the formation of large coal beds in the United States were most favorable in the Pennsylvanian period, formerly known as the Upper Carboniferous. The geological conditions can be determined from the records, but not the reasons for them. Preceding the Pennsylvanian was the Mississippian, formerly known as the lower Carboniferous and still later as the sub-Carboniferous. Dur-ing this time, large bodies of limestone were deposited and at the close f the Mississippian they were warped upward and for along period were eroded. Then there began a period of subsidence, more or less inter-rupted at times, during which the Pennsylvanian strata were deposited (see table on page 2). " These consist of sandstones, limestones and shales, with occasional coal beds: At the beginning of the Pennsylvanian there was subsidence, which allowed the sea to extend over the eroded Mississippian surface to the north and east, extending over eastern and central Texas, a large part of Oklahoma, with a projection into Arkansas, over Kansas and part of Nebraska, all the northern and western part of Missouri, a large part of Iowa except a strip in the north, most of Illinois, practically all of Ken-tucky, northern Tennessee, most of Indiana, all of the eastern part of Ohio, practically all of West Virginia, western Maryland, the west end of Virginia, and a large part of Pennsylvania. The Ozarks were already

Jan 1, 1935

By Clyde E. Williams

Estimates indicate a life of known Lake Superior iron ore reserves of 20 to 30 years. Although some believe the future ore supply will come from foreign sources and will be brought to interior points via the projected Great Lakes-St. Lawrence waterway, and others fear a displacement of the interior steel-producing districts to the Atlantic seaboard, the author has faith that American engineering skill will make possible the use of lean ores from the Lake Superior district. Three general types of Lake Superior ores and ore formations, that represent possible reserves and require beneficiation, are: (1) the wash ores of the western Mesabi range, (2) the partly leached hematitic formations, and (3) the oxidized but largely unleached iron formations. The total tonnage represented by (1) and (2) is not large, but the recovery of iron from present washery tailings would bring on the market the equivalent of nearly one million tons of wash ore, annually. Group 3 comprises the magnetic iron formation of the eastern Mesabi range, the hematitic formations including the taconites of the Mesabi range, and the iron formations of all the other ranges. These formations represent our future supply of iron ore. Their treatment requires intensive research because the bulk of the iron oxide and silica minerals exist in a finely disseminated condition. The possibilities of the adaptation of tables, oil flotation, and other processes warrant extensive study. Cheaper method of agglomeration of the concentrate is essential. Recent developments in better preparation and sizing of blast-furnace charges indicate that substitution of agglomerated ore for fines will increase furnace efficiency and output. If agglomerated beneficiated ore can be shown to rate a per-unit premium for iron contents over the base rate or a premium for structure, the payment of these would greatly assist in enlarging our iron ore supply. Since present methods of taxation of ore reserves, which encourage the rapid depletion of rich ores, will result in using up our rich ores and later on putting domestic producers at a disadvantage in competing with' foreign producers, it would seem highly provident to conserve our rich ores and to increase the use of beneficiated ores as soon as possible.

Jan 1, 1931

By R. S. Archer

IN the microscopic examination of aircraft-engine parts made of heat-treated alloy steels, the writer has been forcibly impressed by the failure of the usual etching processes to disclose any but gross defects in heat treatment. It seemed particularly desirable to bring out the grain size of the steel, which is indicated in the ordinary etching processes chiefly by the change in orientation of structure from grain to grain. After various attempts, a fairly successful method has been found, which is here presented in the hope that it may be of use to those who have occasion to examine these steels in the heat-treated condition. The specimens worked with have been mostly chrome-nickel steels heat treated (that is, hardened and tempered) to a Brinell hardness of around 300. A few experiments with other specimens will be referred to later. Briefly, the method employed consists in etching the steel about 10 min. in a fresh solution of picric acid in ethyl alcohol, and then rubbing off the smudge of carbonaceous matter on moist broadcloth. Different samples of almost identical analysis; heat treatment, and physical properties (including resistance to impact) respond quite differently to this treatment. In some, the grain boundaries are developed quite readily, while iii others, especially ill those whose grain is unusually fine or in which the final hardening heat, has not quite obliterated the previous crystallization, the results are more obscure. The exact time of etching to secure the best results also differs for various samples, and the greatest success is usually attained by a process of "tinkering." Such a process is illustrated in a series of micrographs, the first six of which were taken at a magnification of 300 diameters.

Jan 1, 1919

By P. H. Dudley

I HAVE taken the liberty of calling the researches herein mentioned industrial, to distinguish them from those strictly scientific, where every known appliance is used to insure accuracy in determining principles. The industrial researches are made to ascertain wherein we have failed to embody, in practice, the principles which have been fully demonstrated by the more purely scientific investigations. So far the researches have been mostly confined to the conditions of combustion as used in locomotive furnaces, although we have examined, to some extent, furnaces under marine and stationary boilers. The products of complete combustion are gases, and, knowing what we should have, it is at once shown by analyzing the products whether the desired reactions are taking place. In spite of imperfect furnaces, lack of system in the arrangement of grate-bars and exhaust nozzles, the results are not altogether vitiated, because the analyses are not closer than one-tenth of one per cent., as under the present conditions it is hardly possible to collect gas exactly under the same conditions at different times. All of our industrial operations have developed in the past few years so rapidly, nearly all of them paying, that, until within the past three years, comparatively little attention has been given to their economy outside of the profession. Great corporations have not asked and considered the question in earnest, can we utilize our heat so as to produce the same effect at less cost? The applications of heat are so extensive, entering into every branch of industry, the principal power used to carry on metallurgical processes, to conduct transportation, that its economical generation becomes of universal importance; in fact, its economical generation and application is the leading industrial question of the day. It is stated by those who have given the subject much attention, that in our best steam-engines not over 10 per cent of the theoretical value of the fuel is utilized, and upon locomotives it is far less, probably not exceeding under the most favorable circumstances 5 or 6 per cent. In recent experiments made with the dynagraph, in drawing trains upon the Lake Shore and Michigan Southern Railway from Cleveland to Erie, 95i miles, we found the force required to draw a stock train of 709 tons to be 2,498,396,320 foot-pounds, exclusive of the force to move the locomotive itself. We

Jan 1, 1876

By L. L. Newman

PUBLIC UTILITY GAS PRODUCTION IN 1802, William Murdock first used retort coal gas to light his house and the Boulton and Watt plant where he was employed. For the next three quarters of a century coal served as the principal raw material for the manufacture of city gas for general distribution. Coal continued to hold its predominant position for another half century after Prof. Thaddeus C. Lowe developed the first practical method of enriching water gas with cracked-oil vapors in an integrated operation. This position, however, was no longer maintained through the medium of direct carbonization of coal in retorts but as a result of using anthracite or coke as the generator fuel in carburretted water-gas machines. The early water-gas machines were extremely crude and the consumption of both oil and generator fuel was very high. However, the cost of installation was considerably lower than for any coal-gas system having the equivalent gas-making capacity, the labor involved was small, and the water-gas machine could be started up and shut down quickly. It thus proved very useful as standby equipment and in taking peak loads from the coal-gas plants. The flexibility of the water-gas machine, furthermore, made it possible to change the candlepower of the gas readily to suit the required conditions. Later, when calorific value replaced candlepower as the standard of gas quality, the water-gas machine was found to be equally flexible in keeping the city gas under complete and convenient control. No basic improvements were made in the Lowe carburetted water-gas process until 1898, when means were added to provide for regular reversals of the flow of steam through the fuel bed. By judicious proportioning of the quantities of up-run and down-run steam, it became possible for the operator to control the hardness and position of the clinker to a degree that previously had been unattainable. Also in 1898, the first by-product coke plant in America to supply city gas was built at Everett, Massachusetts. Later many other by-product plants, of greatly improved design and capacity, were built, but not primarily for city-gas production, chiefly because of the relatively high investment cost per unit of gas made. Cheaper plant construction has been the subject of serious study, and some progress is expected, but other factors, such as plant life,

Jan 1, 1953

By Andrew Hodge

ISSUES IN MINING LABOR The examination of mining labor issues is often confined to health, and safety. There are other issues, including the present state of mining manpower availability and utilization, and the nature of mineral industries' industrial relations, which are worthy of consideration. The state of the labor market for mining skills, the availability and utilization of mining engineers and related disciplines, the state of research and its employment of scientists and engineers, and the condition of mining industrial relations with all these groups, all have an important effect on the viability and economic health of the minerals production sector. PRODUCTION LABOR Why examine an industry's production labor market? People involved in an industry should be aware of what labor supplies will be relative to industry requirements. This advance information allows industry and government to plan ahead to alleviate problems by moving to affect labor supplies or to accommodate production to expected labor supplies. This is less costly and less painful than responding after the fact to labor market changes. Any industry requires some form of labor. Labor is especially important to the mining industry. Mining labor is well paid. Average annual earnings are higher than in manufacturing. Average hourly wages are also higher. Payroll costs form a high percentage of total cost in coal mining and nonmetallic minerals mining. In metal mining the percentage is comparable to the average for manufacturing. Payroll cost in oil and gas extraction is quite low, but a major proportion of cost is in the form of income to proprietors, i.e., unincorporated businesses. Mining labor is worthy of specific attention. The minerals extraction labor is unique in many ways. Mining labor and especially underground miners are differentiated from other "unskilled" labor. Miners cannot be considered as part of a larger labor pool. The mining labor market has exhibited a unique combination of characteristics. Mining is the only large sector of United States employment in which hourly wages are high and continuing to rise, yet employment declines. Although industry has introduced new labor-saving investments, and labor requirements continue to decline, there is evidence of a mining labor shortage. Specific problems have arisen in the mining labor market such as a present labor shortage in nonfuels mining. Understanding the causes and remedies for these specific problems is also important. These various problems and questions may be handled in a unified manner by examining the relationships of certain economic variables. The relationship that exists between changes in output, employment, labor productivity, and hours worked per week may be stated explicitly:

Jan 1, 1976

By C. V. Millikan

When a flowing oil well is being drilled in with cable tools, it is difficult to determine when an additional streak of pay sand is drilled. By placing a gas meter on the gas-release line from the oil and gas separator, any increase in volume of gas that comes with oil production is recorded. In addition to the better knowledge of sand conditions, these data are a valuable aid in determining the size and depth of shots, plugging off water, and estimating ultimate production. The meter also gives a record of operation while the well is drilling in; and if allowed to remain on the well after completion will give information that may lead to a more efficient recovery of the oil from the sand. A VERTICAL cross section of any oil sand will show great variation in porosity and oil content. In some sands, the entire thickness contains oil, the variation being only the degree of porosity or oil content, but more often the pay streaks are distinctly separated by shells or barren streaks. These pay strata vary in number and may be thin or thick. The total thickness of the sand may be several tens of feet while the part containing oil may be only 1 or 2 ft. thick. The amount of production is not proportional to the thickness of the sand but rather the thickness of the pay streaks. If the total thickness of the sand or the amount that can be drilled is small, or if the initial production is small, the depth at which each stratum of pay is encountered can be determined sufficiently accurately for all present economic purposes. However, when drilling through sand of considerable thickness, giving large initial production, especially where conditions necessitate that the production go through the same gas trap with that from one or more wells already producing, it is difficult to determine the depth at which the pay strata are encountered even accurately enough to guide the placing of shots, and small pay streaks are apt not to be recognized at all.

Jan 9, 1925

By Frederick Prime

THE Great or Cumberland Valley, which (under a variety of names) extends from Canada, through Vermont, Massachusetts, Connecticut, New York, Pennsylvania, Maryland, Virginia, and East Tennessee, to Alabama, is composed in part of limestones lying immediately above the Potsdam sandstone. Geologically, they belong to the era between the Potsdam and Trenton, and are commonly termed Calciferous. A peculiarity of these limestones is their great richness in limonite or brown hematite ores, which form a large part of the charges of the many blast-furnaces situated on their outcrops. The mines from which the ores are obtained are (properly speaking) only pits or quarries, from which the ore is extracted by means of picks or shovels, powder being rarely employed. The ore does not occur casually at any point in the limestone, but forms regular lines, following apparently the 'outcrops of certain beds. In Lehigh County, Penn., where I have been engaged on the Geological Survey of' the State, during the past season, there are three or four of these lines. During the progress of the survey I was much struck by the fact that the two most important and promising lines of outcrop were, one at the base of the crystalline schists (forming the South or Lehigh Mountain), and overlying the Potsdam sandstone conformably; the other, near the line of junction of the calciferous limestone with the slates of the Cincinnati epoch. The mines along these two lines, following the topography of the country, were in place, richer and more permanent than those of the belts between, which were generally leaner. A peculiarity of these two lines of outcrop, and one to which I particularly desire to draw attention, is the occurrence of what I at first mistook for a highly altered slaty limestone, but which subsequent analysis proved to consist in great part of damourite (hydrated potash mica). The following are analyses of this damourite slate I. From Fogelsville, Lehigh County, within a few hundred feet of the contact of limestone and slate, by Dr. F. A. Genth. II. From Hensingerville, Lehigh County, within 300 feet of gneiss, by Mr. Sydney Castle, of the University of Pennsylvania. III. From Allentown, Lehigh County, within 150 feet of con-

Jan 1, 1875

By J. C. Sullivan, W. A. Knoll

THE sinking of a new shaft at the Newport mine, Ironwood, Mich., was started in May 1931 and completed on Aug. 3, 1932. During this period, 2665 ft. of shaft in granite was completed, at an average advance of 6 ft. per 24 hr. In November of 1930, experimental work was con- ducted on 65 ft. of shaft through 22 ft. of overburden where ledge was encountered, and this work convinced the operators that all drilling could be done with vertical holes with the blasting relief to a 4%-in. hole drilled vertically in the center of the cut. The reason for not adopting the conventional V-cut was to get away from damaging the shaft steel. The blasting in a V-cut naturally tends to throw the broken material upward, but with the cut as adopted the relief was in a horizontal direction to a large extent. The scheme of mucking employed made it necessary to keep the steel shaft sets within 50 ft. of the bottom at all times. This could not be done without serious damage with a V-cut when blasting in granite. The cut as drilled also broke 10.83 ft. per round of drilling, which was considerably more than the experience with a V-cut in the same material. The extended cut reduced proportionately the delays for charging, blowing smoke and handling drilling equipment in the shaft. Another advantage was the ease in drilling vertical over inclined holes, and the preservation of the proper spacing of the drill holes at the bottom of the cut. DRILLING Air was carried down the shaft in an 8-in. flanged pipe line at a pres- sure ranging from 95 to 100 lb. This line was extended to within 100 ft. of the bottom, where a valve and a 4 by 4 by 6-ft. tee was connected to it. To each side of the tee was connected a nipple and elbow, the resulting span of the two elbows being about 4 ft. Lengths of short 3-in. hoses

Jan 1, 1938

By Carl F. Floe, Michael B. Bever

TRE solubility of hydrogen in molten copper-tin alloys is of both practical and theoretical interest. From a practical standpoint, data on the equilibrium solubility as a function of temperature, pressure and alloy composition are valuable for a better understanding of porosity problems in bronze castings. From the theoretical point of view the determination of the hydrogen-copper-tin equilibrium is of interest since it extends the laws governing the solution of gases in metals. This paper presents the results of an investigation of the solubility of hydrogen in representative compositions of the copper-tin system at temperatures ranging from above the liquidus to 1300°C. and at pressures from less than 50 mm. of mercury to about atmospheric. REVIEW OF PREVIOUS WORK The solubility of hydrogen in copper was determined by Sieverts and Krumbhaarl in 1910 and by Roentgen and Moeller2 in 1934. Their values are in fair agreement. In 1926 Iwasé3 reported results that were very much higher. The published data on the solubility of hydrogen in tin do not agree. Smithells4 states that no reliable data are available. According to Sieverts and Krumbhaar,5 hydrogen is insoluble in tin. Bircumshaw,6 on the other hand, found a definite solubility at 800°C. The latter's experimental procedure did not provide for stirring of the metal and in his opinion he failed to reach equilibrium. Iwasé3 again reported large solubility values. For copper alloys, Sieverts and Krumbhaar6 distinguished between alloying elements that do not markedly affect the solubility of hydrogen, elements that increase the solubility, and elements that reduce it. They named gold, tin, and aluminum as examples of this last group and reported hydrogen solubility data at 1225°C. for the copper-rich side of these alloy systems at atmospheric pressure. Without giving experimental results, they stated that the amount of hydrogen dissolved by liquid copper alloys is proportional to the square root of the pressure as in pure metals. These authors suggested that in a limited way the effect of an alloying element on the solubility of a gas is related to the constitution diagram for the alloy system. Sieverts7 also called attention to the fact that the curve of hydrogen solubility versus composition of copper-tin alloys shows a sharp change of direction at the composition of Cu3Sn and suggested that this compound persists at least to some extent in the molten state. Iwas3é reported large hydrogen solubility values for several compositions of copper- tin alloys, which appear to be in error.

Jan 1, 1944

By C. S. Matthews, H. C. Lefkovits

The purposes of this study are (a) to determine the accuracy of a previously proposed method for calclrlating average reservoir pressure and (b) to find a method for estimating the shape of the drainage area of each well in a bounded reservoir. Both numerical and experimental methods are used to determine the pressure distribution and the location of drainage bounrlaries in idealized reservoirs at steady state. A number of photographs are included which show flowlines and drainage areas in reservoir models of various shapes. Results from these studies are then compared with those from the previously proposed method for calculating average reservoir pressure.' It is concluded that the previously proposed method is sufficiently accurate for most reservoir engineering purposes. In addition, some simple methods are given for estimation of .shapes of drainage boundaries. INTRODUCTION A method for the determination of the average Pressure in a bounded reservoir was previously developed by Matthews, Brons, and Hazebroek,1 and presented at the Petroleum Branch Fall Meeting in 1953.† In aP- plying this method, the reservoir was first divided into drainage volumes; second, the average pressure in each drainage volume was calculated; and third, these drainage volume pressures were averaged volumetrically to give the average pressure in the reservoir. It was shown that each well's individual drainage volume, at steady state, is proportional to the well's production rate; however. the question of how to estimate accurately the shape of these drainage volumes could not be answered. Furthermore, in calculating the average pressure for each drainage area, the actual drainage areas, which are in general quite asymmetric in shape, are replaced with one of the symmetric prototypes given in T.P. 3876. A question may then be raised as to how accurately the symmetrical figures depict the pressure behavior of the actual unsymmetrical drainage areas. The study reported on in the present paper was made in an attempt to shed light on the above questions. METHODS It was shown in T.P. 3876 that after a period of steady rate of withdrawal the rate of pressure decline becomes constant at every point in a bounded reservoir containing a single-phase fluid whose compressibility is small and constant and whose viscosity is con-

Jan 1, 1956

By W. D. Robertson

A considerable quantity of experimental data is available on the effect of time, temperature, work-hardening and composition on the mechanical properties and corrosion resistance of aluminum alloys. There is, however, little unity of purpose or generality in most of the studies and, because the number of variables is large, the results often are not applicable to the problems that arise in practice. Furthermore, the customary expression of the effect of different variables as separate curves or as three-dimensional diagrams with time, temperature and the dependent variables as coordinates, renders the task of selecting the optimum time and temperature of precipitation treatment, with respect to their simultaneous but unequal etfect on the various properties, exceedingly difficult. The introduction of precipitation treatments to raise the yield strength of 24s-type alloys has created a need for a method of correlating and summarizing the effect of time and temperature on the mechanical properties and susceptibility to inter-crystalline corrosion. Correlation is particularly desirable because the choice of time and temperature is of necessity a compromise to achieve the best possible combination of properties, and the optimum conditions cannot he accurately specified unless the data are in a form in which the alternatives can be readily compared. Therefore, the work described here was undertaken to find a common relationship that would be capable of expressing the effect of precipitation time and temperature on the various properties and by means of which the relative effects could be correlated and their interpretation facilitated. Review of Previous Work In connection with an investigation of the interrelation of age-hardening and creep performance of nickel-silicon-copper alloys, Jenkins and Bucknalll demonstrated that the time required to attain maximum hardness and tensile strength could be expressed by a relationship of the form: t = K • io"^ (i) where t is the time in hours and T the temperature of aging, expressed in degrees absolute, and m and K are constants. They also pointed out that this expression is analogous to that which describes the change of the diffusion coefficient D with temperature; namely, D = Ae-~/m (2) Later, Cohen used this relationship in studies of the mechanism of age-hardening of a silver.rich copper alloyZ and of duralumin.3

Jan 1, 1946

By L. D. Anderson

WHEN, after years of troublous experiences in roasting sulfide ores with heavy dust and fume losses resulting from the equipment and methods first available, there appeared on the, scene of metallurgy that revolutionary process known as sintering, it was felt that at last there had been found the ideal method for preparing sulfide ores for blast-furnace reduction. Not only were the sulfides roasted but also the fine oxidized ores were bound together with them in strong porous cellular masses which were in the best possible condition for reduction. With the experiences gained in the manipulation of the Huntington-Heberlein, Carmichael-Bradford, and Dwight & Lloyd processes there developed a refinement of detail which brought the whole plan of roasting by sintering to a high plane of perfection. But that metallurgy is never stationary is revealed by the fact that changes in milling practice, particularly the development of flotation, have introduced a new set of problems in sintering itself. Inasmuch as it is felt that these problems have not yet been solved in an entirely satisfactory manner this paper is written to record the present practice of the Salt Lake Valley smelters with the hope that there will be brought forth such discussion as may perhaps lead to still better practice. By far the greater proportion of the sulfides smelted today are flotation concentrates. Usually they are high grade, sometimes as high as 70 per cent. and more in lead. They are extremely fine, many mills grinding the ore so that from 60 to 80 per cent. will pass through screens of 200 mesh. The physical condition in which many of these concentrates reach the smelters is disconcerting to the metallurgists. Some are of about the consistency of putty. Others are of a sticky, slimy nature. Others again, dried to the limit, are veritable powders. Remembering that the down-draft sintering charge for the best results must be porous enough to let air be drawn through it reasonably well, must be thoroughly mixed, and must have some coarse material in it to segregate out and form a layer on the grates, it will be understood that the advent of this extremely fine material has made necessary still further elaboration in the equipment and processes of preparing sulfides for the blast furnaces, all of which is expensive. The high metal contents of the concentrates

Jan 1, 1929

By H. D. Colson, Robert A. Rapp

When a binary alloy is oxidized to form simultaneously an internal oxidation zone and an external scale which grows at a constant rate, the oxidation should reach a condition of steady shale, in which the internal oxidation zone is maintained at a time-independent thickness. Assuming an ideal model for the steady-state oxidation, the diffusion equation is solved for the steudy-state concentration profiles for oxygen and alloying- element in the metal. A theoretical prediction of' the steady-state thickness of the internal oxidation zone is made in terms of the experimental parameters. FOR the oxidation of binary alloys, Rhines, Johnson, and Anderson,1 as well as Mask: have derived equations describing the kinetics for the simultaneous formation of an internal oxidation zone and an external scale which was assumed to mow according to a parabolic rate law. Experimental determinations of internal oxidation zone thicknesses beneath a Cu2O scale for Cu-Be and Cu-A1 alloys3,4 have shown some deviation from Maak's theoretical expressions, because the ideal model assumed for the calculation is not met experimentally. Some pure metals, such as columbium and tantalum oxidize at elevated temperatures and high oxygen pressures to form nonprotec-tive external scales which thicken at a constant rate. If such a base metal is alloyed with a solute element which may form a more stable oxide than the solvent oxide, then internal oxidation of solute may occur beneath the growing external scale. A review of the internal oxidation of alloys has been published recently.5 The purpose of this paper is to analyze theoretically for a binary alloy the kinetics for the simultaneous formation of an internal oxidation zone and an external scale which grows at a constant rate. Consider an alloy A-B in which A is the more-noble solvent and B is the less-noble solute. The solute oxide is assumed to precipitate in internal oxidation as stoichiometric particles of BO, which are assumed to have a negligible solubility product in the A matrix. It is further assumed that the diffusion of oxygen through the zone of internal oxidation is not impeded by previously precipitated BO, particles. The specimen is assumed to be sufficiently thick so that the solute content in the center of the specimen does not change. For consistency: the following notation of Maak2 has been used:

Jan 1, 1967

By H. M. Chance, T. M. Chance

The term 'Llow-sulfur coal," as used in this discussion, is limited to coals containing less, or very little more, than 1 per cent. sulfur. For certain purposes it might be advantageous to include coals that contain as much as 1.25 per cent. sulfur, because such coals have been considered as available for making metallurgic coke of fair grade; but the same reasoning might apply to coals containing as much as.1 1/2 per cent. sulfur, if facilities exist for utilizing such coal by admixture with coal containing less sulfur. , In Pennsylvania, it is not possible to define the exact geographic limits of the areas in which coals relatively low in sulfur exist, because variations in the percentage of sulfur occur irregularly and often abruptly. It is not uncommon to find areas, more or less circumscribed in extent, in which the coal is relatively high in sulfur although all the surrounding territory contains low-sulfur coal; and, similarly, small areas of low-sul. fur coal exist in districts where the coal is normally high in sulfur. These generalizations apply, with few exceptions, to the whole area underlaid with bituminous coal in the State of Pennsylvania, and also to each of the individual beds of coal in this state. Pennsylvania is poorly supplied with coals of the low-sulfur class. We find, however, as an offset to this condition, very large areas in which coal ranging from 1 to 2 1/2 per cent. sulfur exists in beds of good workable thickness. This coal, by washing, can be reduced in sulfur low enough to make coke of a high grade. While a considerable tonnage of workable low-sulfur coal remains in the Pennsylvania bituminous districts, it has been necessary to turn to the areas of higher sulfur coal for the supply of metallurgical coke. This utilization of the higher sulfur areas has been made possible either by washing or by selective mining. Washing.—Fine crushing of the entire feed is not generally necessary to the successful washing of Pennsylvania coals. This is due to the fact that the pyrite is rarely finely and uniformly disseminated throughout the coal but is usually confined to high-sulfur benches in the bed or to concentrations on the cleavage planes of the coal. Hence, by graded crushing and sizing it is frequently possible to at once reclaim those portions of the coal bed containing coal that is relatively free from pyrite.

Jan 1, 1920

By William Metcalf

It is the object of this paper to oppose unnecessary changes, and the introduction of new and confusing terms. From the earliest times of which we have ally record on the subject, iron has been divided into general classes. Whether iron was first known in the form of wrought iron or of steel, is a matter of no importance; but at the time when cast iron first became a prominent article of commerce, wrought iron and steel were old products— steel, at that time, being generally made from wrought iron by the process of cementation. As steel was then properly defined as iron containing more carbon than wrought iron, so cast iron was appropriately defined as iron containing more carbon than steel. Until the year 1776, when Huntsman first began the manufacture of a new kind of iron by melting wrought iron and steel in crucibles, the above definitions were all that could be desired. At first, probably, owing to imperfect appliances, only a highly carburized iron was melted in crucibles, and this led to its being called cast steel. If our ancestors had found a name for this material not involving the use of the word steel, we would have been saved the trouble of the present discussion. As the arts developed, new uses were found for steel, and the products of the crucible were varied, until at the present day it is quite common to find steel containing no more carbon than average wrought iron, and other steel containing nearly or quite as much carbon as some cast iron. All of these various products of the crucible have retained, or received, the name cast steel, usually abbreviated to the simple word steel, without caus-ing any confusion among producers or consumers in regard to terms or their meaning. In 1865, twenty-one years ago, the Bessemer process was introduced ; this was followed in a few years by the Siemens-Martin process, and the products of both were at once, and have ever since been, called steel, from the fact that they were identical in chemical and physical properties with crucible cast steel. At the present time, then, we have three subdivisions of cast steel, viz.: Crucible cast steel, Bessemer cast steel, and Siemens-Martin,

By J. F. Myers, F. M. Lewis

THE selection of the proper type of flotation machine involves the consideration of a wide variety of factors. Under any condition, all types of machines will promote some kind of separation. Obviously, the correct way of deciding which type of machine is best suited for a particular problem would be to set up all types of machines and test them out in a competitive manner, but the vast number of small concentrating plants are unable to make such complete and exhaustive tests. The experience of the authors of this paper indicates that if all the factors involved in any particular problem can be determined, and if all the flotation-machine characteristics are understood, some basis for selection could be arrived at other than actual comparison. This paper is presented to show how the process factors and machine characteristics have been combined at the mills of the Tennessee Copper Co. from studies of several types of flotation machines. At the two mills of the Tennessee Copper Co. in the Ducktown Basin of Tennessee, four distinct flotation separations are made on the complex sulphide ore. Three different concentrates are produced from the ore-in the order of their importance: iron concentrate, copper concentrate, and zinc concentrate. Four different types of flotation machines are used. The selection of these four machines, for the plant operation, was based upon the study and operating experience of the machine units shown in the following list: Fagergren machine; square cell, size 56 inches Fagergren machine; level type, size 56 inches Denver machine; conical disk impeller, size 24 inches Denver machine; receded disk impeller, size 24 inches Minerals Separation Sub-A, size 24 inches Munro-Pearce deep cell, pneumatic Southwestern air machine, Hunt principle To date the study of flotation machines has been confined almost entirely to the rougher circuits. The various cleaning operations, being relatively a much simpler matter, have not been investigated so thoroughly. Table 1 shows a typical analysis of the two ores as well as of the mineral content. []

Jan 1, 1944

By A. G. Suydam

Ancient as is the art of producing copper, so ancient is one of its eternal problems: refractories. Looking backward, in the light of present knowledge, clouded though it be, one cannot avoid a sense of profound respect for the patience, acumen and courage of those who have wrought so successfully despite difficulties, a more accurate understanding of which seems merely to accentuate. The problem of refractories arises from the necessity for constructing containers in which to bring natural ores into thermal solution in order to effect reduction and separation of the valuable metal content and free it of undesirable contamination while producing a waste slag. The very forces known to produce thermal solution of sufficient liquidity are necessarily destructive of exposed refractory linings in proportions varying inversely with thermal conductivity, directly with the porosity and ease of fluxing of the refractories used, and directly with the temperatures employed. Beyond this, mechanical forces are set up within the refractory lining incident to rapid heating or cooling, shrinkage at high temperatures, and unequal or excessive loading, that frequently pass the elastic limit, causing spalling or distortion. The effects of these forces are often accentuated by the necessity of providing at the same time as hot a bath and as cool a container as are consistent with fuel economy. Evolution in the Use of Refractories Clay Brick.—Fireclay and clay refractories had to yield wherever they were in contact with slags rich in basic oxides, first because of the combining power of those oxides with free silica and secondly because of the tendency of alumina to form either aluminates or alumina-silicates of varying complexity. Of no less importance, the incipient fusion point was low as compared with good clay brick of today, while the brick lacked strength at high temperatures. Expansion was slight, therefore it was difficult to make and maintain tight walls, roof, or bottom. However, the spalling tendency was low because of some of these properties and clay brick have retained their place in roasting furnaces, boiler furnace linings, and in the upper walls of some of the reverberatory types such as some refining, anode and wire-bar furnaces. They have served often and most efficiently for hot patching.

Jan 1, 1934

By G. H. Wilson

INTRODUCED in 1946 to serve a need in power- plant operation, closed-circuit TV has been used by well over 200 organizations in approximately 25 different industries. Known as industrial television, or simply ITV, it can be described as a private system wherein the television signal is restricted in distribution, usually by confinement within co-axial cable that directly connects the TV camera to one or several monitors, Figs. 1, 2. The picture is continuous and transmission is instantaneous, permit- ting an observer to see an operation that may be too distant, too inaccessible, or too dangerous to be viewed directly. Destructive testing or the machining of high explosives can now be conducted hundreds of feet away by personnel who still have close control through the eyes of the TV camera. It is also possible for one man to control operations formerly requiring the co-ordinated efforts of several workers. For example, at a large midwestern cement plant conveyance of limestone from primary crusher to raw mill and loading into five storage bins once necessitated the work of two men, one having little to do but prevent spilling of material by manually moving the tripper on the belt conveyor as occasion required. TV cameras mounted on the tripper now provide bin level indication to the conveyor operator at the crusher position so he is able to control the entire loading operation remotely, Fig. 3. By means of a switch, the picture from either camera is alternately available on a single viewer, or monitor, Fig. 4. Each camera is mounted on the tripper by means of a simple adjustable support and looks down into the bin, which is identified by the number of cross members on the vertical rod. Each associated power unit is located on a platform above the camera, Fig. 5. This centralized control by means of TV often has produced superior results, and in many instancés saving in operating costs has been sufficient to write off equipment costs within six months to a year.

Jan 7, 1954