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By Edmund Shaw

In the year just past there were produced in the United States about 170,000,000 tons of sand and gravel. Much of this was pit-run material used for gravelling roads and as railroad ballast on lines that did not carry heavy traffic. But more than half of it was marketed as washed and sized, or graded, material. The methods used for preparing sand and gravel for the market have long been used in ore dressing and, as in ore dressing, depend on differences in the specific gravity of two substances or in the size or weight of particles. But many changes in the design and operation of plants and machines have been necessary. In ore dressing, the concentrate is only a small part of the feed; in sand and gravel washing, it is much the larger part of the feed. In addition, such close work as is needed when concentrating a metallic ore is not needed when washing gravel; the ability to put through a large tonnage is more important, and sizing, which is only a preliminary process in ore dressing, is an end to be attained. Rock crushers are found in most sand and gravel plants and they are used to break up the larger pieces from the deposit (known as boulders and cobbles) which are removed by a scalping screen. The crusher discharge is usually sent back to the scalping screen, the perforations in this screen setting the maximum size of the finished product. Washing Washing is to prepare sand and gravel so that they may be used as aggregates in concrete and wall plaster and in various processes in which impurities would harm the product. At one end of the scale of washed materials may stand ordinary concrete sand, which in some states may contain as much as 3 per cent, of clay and still be used in highway concrete construction. At the other end will stand the silica sand used for making plate glass, which must be washed so clean that the impurities that can be removed by washing do not exceed a few hundredths of a per cent. The methods and machinery that would produce one of these

Jan 1, 1926

By Reginald S. Dean

Manganous oxide is readily soluble in concentrated ammonia solutions containing ammonium salts. Lixiviants of ammonia and ammonium carbamate permit ready extraction of manganese from reduced ores and the manganese in such solutions may be precipitated by heating to transform the carbamate to carbonate. THE widespread occurrence of manganese in low grade oxide and carbonate ores not amenable to mechanical concentration has led to extensive investigations of hydrometallurgical methods for producing a pure manganese compound suitable for further treatment. Manganese carbonate is the preferable compound. This product when fully crystalline and of not too fine crystal size is easily filtrable and stable in air. It can be converted to other compounds such as the oxides by heating in air or can be reacted with acids for producing salts. A useful hydrometallurgical process must produce relatively concentrated solutions that can be purified easily, reagents must be cyclically used, and heat requirements must be small. Neither the ammonium sulphate nor sulphur dioxide leaching processes that have been tested extensively fulfill these requirements. Other heretofore proposed processes have obvious limitations and have not been tried on a large scale. The present process is based on the discovery by the writer of a new group of aqueous manganese-ammonia complex solutions highly concentrated in ammonia, which permit rapid solution of manganous oxide to concentrations of 80 to 100 g Mn per liter and from which a fully crystalline, easily filtrable manganese carbonate is precipitated by the addition of carbon dioxide and partial ammonia removal. Although the process may be carried out with many ammonium salts, commercial advantages dictate the use of ammonium carbamate, which is obtained when CO2 is passed into concentrated aqueous solutions of ammonia. If the carbamate is used, the only reagents, ammonia and CO2, are volatile and may therefore be recovered from solutions and residues by heating, thus eliminating washing and extensive evaporation. Impurities are controlled easily as most metal oxides are either insoluble in the lixiviant or fail to precipitate with the manganese carbonate. Others are controlled by sulphide addition. The process has been tested extensively on a small scale on a wide variety of ores, including Three Kids, Artillery Peak, Cuyuna, and Chamberlain, as repre-

Jan 1, 1953

By J. E. Sandor, P. F. Schmidt

A general review of the present knowledge of the semiconductor/oxide interface is given, with emphasis on silicon and germanium. The electrical properties of clean surfaces and the changes that occur upon oxidation are described. A brief disczcssion of the methods and mechanisms of oxidation of silicon is given, and the interaction between the semiconductor substrate and the oxide phase is considered. Physical properties of the oxide film, charge storage effects due to the dielectric, and some device applications of oxide films on semiconductors are discussed. THIS paper will be heavily preoccupied with the elemental semiconductors germanium and silicon. Undoubtedly some injustice is done thereby to other semiconductor-oxide systems, but it is not readily possible to cover all aspects of so vast a field in the present review. In considering the semiconductor/oxide interface, we may start out by discussing briefly an idealized clean semiconductor surface, and may then follow the changes brought about by oxidation, as the oxide is allowed to grow progressively thicker. The references given are not a complete list, but are to be taken as guides to the literature. Tamml suggested in 1933, based upon the study of a one-dimensional asymmetrical potential model, that localized surface states may appear at the surface of a crystalline lattice; it was pointed out by Fowler that these states should occur in pairs. shockley3 examined the origin of such surface states on the basis of a more general one-dimensional model and found that surface states may appear in the forbidden region between the highest filled and the lowest vacant band. This happens when the two bands overlap, as, for instance, the "s" and ('p" bands of the diamond structure. In a three-dimensional model these levels would produce a surface band which is half-filled for diamond, and the number of surface states should be approximately equal to the number of surface atoms. This picture of the surface has been refined by more recent theoretical work, like Handler's4 and Koutecky and Tomasek's~ without introducing essential modifications. When these concepts were applied to semiconduc-

Jan 1, 1965

By E. G. Woodruff

(Butte Meeting, August, 1913.) FEW authors of treatises and papers on engineering subjects have . given adequate attention to topographic maps.. The statement applies especially to mining engineering in all branches. Even those who have discussed such maps have treated the subject only in a general way. Therefore it is proposed to outline in this paper a few of the uncommon, yet important relationships which topographic maps and their by-product, structure-contour maps, have to modern methods of mining investigation and development when the facts depicted on such maps are properly interpreted. Topography, as suggested by the etymology of the word, menus a detailed description of particular places. Written descriptions have been found less effective than the pictorial representations, therefore attempts have been made in various ways to picture the surface features of places. Lines and shading have been used, hachures drawn, and, finally, the contour topographic map. To a large extent this style of snap is the result of the demands of engineers. It is designed to meet their needs far more than those of the man untrained in engineering. In fact, the average man obtains a better idea of the topography of an area from the hachure system than from contour maps. . Since the maps. have been made chiefly for the use of the engineer, they ought to meet his demands on the one hand, and, on the other, should be used by him to the fullest extent. Such maps, when properly made, accurately portray a portion of the earth's surface and should present the topography better than a personal examination of the area without a map could present it, because the person making such examination views only a limited portion of the surface at a time, and estimates distances only roughly with his eye. Let the engineer consider carefully the fact that in many instances the topographic map is superior to a personal examination of the surface features of a property because the map is based on careful instrumental measurements, whereas the eye gives imperfect data because it can be used merely for the estimation and

Jan 6, 1913

By N. H. MacMillan, O. C. Dias

Recent work by Westwood et al. (reviewed in Refs. 1-6) has established that many rocks, minerals, ceramics, and glasses exhibit phenomenologically similar chemomechanical (Rebinder) effects when deformed in different liquid environments, apparently as the result of chemisorption-induced variations in their near-surface flow and flow-dependent fracture behavior. In particular, it appears that there exists an empirical, but apparently general, correlation between the near-surface flow stress of an inorganic nonmetal and its surface charge- namely, that such a solid is hardest at its zero point of charge (i.e., when its zeta potential [ ] = 0) and softens as [ ] increases, regardless of the sign of zeta. Moreover, because near-surface flow and fracture phenomena are two of the important determinants of the rates of machining and comminution processes, both Westwood et al. and others7 have been able to use this so-called "[ ]-correlation" to develop cutting fluids and grinding aids that in many instances have given rise to several fold increases in performance. In addition, Westwood et al. have demonstrated that both aqueous and organic environments can give rise to similar improvements in cutting rate for a given combination of tool and workpiece, provided that both impart the same surface charge to the work- piece (i.e., transfer the same number of electrons to or from its surface). This last finding implies that in any application it should always be possible to find some cutting fluid that is at once effective, cheap, nontoxic, and nonpolluting. Thus, reports of apparently similar environmental influences on the mechanical behavior of diamond,8 certain organic crystals and polymers,9-14 and coa1-15-21 suggest that it is pertinent to ask: (a) whether the [ ]-correlation (or any analogous relationship) extends to coal; and (b), if so, whether this relationship can be used to guide the development of superior aids for grinding coal. Accordingly, correlations have been sought between (1) the zeta potentials, (2) the hardnesses, and (3 and 4) the drilling and grinding characteristics of coals of different rank in different aqueous and organic environments. This paper reports the results of that search.

Jan 1, 1980

By S. J. Hardison

IN the fall of 1912, the appearance of water in the oil of the Nevada Petroleum Co., Coalinga, Cal., made necessary the installation of a dehydrating plant to reduce the water below the 3 per cent. limit prescribed by the agency. Unlike the mining industry, technical literature of the oil industry is limited and extremely unsatisfactory. Until the recent efforts of the Petroleum and Gas Committee of the American Institute of Mining Engineers, no concerted movement has been instituted to secure publication of papers dealing with the problems of the oil business, and because of the additional fact that dehydrating of oil has not been practiced in California to any extent up to comparatively recent time, it was found necessary to experiment in order to determine the most satisfactory plan for this purpose. It is easy to write regarding successful enterprises, but, while not so pleasant, it is equally desirable to write of failures so that others may be saved the loss incident to such investments. The water in this oil occurs both free and as an emulsion. Free water easily settles out, but the emulsion requires treatment. So far as can be determined, the emulsion consists of globules of water surrounded and enveloped by a film of, oil. Starting with this hypothesis, the theory has been evolved that in order to break up this emulsion the water must be heated at least to boiling point, when an explosion takes place destroying the globule. Unfortunately, this condition was not recognized in the installation of the first plant, which was planned on the following lines: A heater was arranged so that all the oil from the wells could be heated before reaching the shipping tanks, these being already fitted with coils for steam heating. Tanks were filled with about 4 ft. of water, live steam was turned into the coils and the water brought nearly to the boiling point, when the heated oil was run in. This for a time was partly successful, but the length of time necessary to apply this heat was too great for practical operating.

Jan 3, 1915

By Charles Pack

Die castings may be defined as metal castings made by forcing molten metal, under pressure, into a metallic mold or die. It is necessary to keep this definition in mind to avoid confusing this process with other permanent-mold casting processes. The fundamental principles of the process have been known and practised many years. The simplest application is embodied in the modern linotype machine in which molten metal (usually tin-lead alloy) is forced under pressure into a metallic mold. The pressure is derived from a piston and cylinder immersed in the molten metal. Progress in the art of die casting may conveniently be divided into three groups: Machine for imparting pressure to the metal, material for the die or mold, casting alloys. The problem of delivering molten metal under pressure into a die is comparatively simple, when dealing with low-fusing-point alloys, as the alloys of lead and tin, but it is much more complicated when dealing with metals of higher fusing points, such as the alloys of zinc, aluminum, and copper. Although the art of die casting is comparatively new and, to a large extent, unknown, the records of the patent office are replete with patents on the subject. Fig. 1 shows the Underwood machine patented in 1902; this is probably one of the first machines designed for the production of commercial die castings. The relation of this machine to the linotype casting machine is clearly apparent. A cylinder and piston are immersed in the molten metal, the application of power to this piston forcing the molten metal, under pressure, into the mold or die. The Doehler machine, Fig. 2, patented in 1907, is based on the same general principles. This machine is used to a large extent at the present time, throughout the United States, for the production of zinc, tin, and lead alloy die castings. In the machine shown in Fig. 3, patented by Doehler in 1910, compressed air is used for forcing the metal into the die. In Fig. 4 is shown another of this type of machine. Here compressed air is applied to the surface of the molten metal to force it into the die. In a machine patented by Chandler in 1914, shown in Fig. 5, the

Jan 1, 1919

By C. P. McCormack

The Cuyuna manganiferous iron ores can be a principal source of manganese for the iron and steel industry in the United States, provided metallurgical methods as a whole are adjusted so as to use run-of-mine ore. The use of manganese in steelmaking is growing. Increasing amounts of impurities in raw materials call for more manganese, a constant cheap supply of which is wanted. There are few deposits of ore in the United States carrying over 35 per cent. manganese that can be mined and marketed at a profit in normal times. We are largely dependent on foreign ores. The small domestic deposits should rightly be held in reserve for an emergency, such as a war, when importation might cease. Even the production from lean ores, concentrated it may be, might not carry us through a protracted stringency. The Cuyuna district is, therefore, during normal times capable of supplying a large total of manganese. The ores are iron ores containing 5 to 25 per cent. of manganese with the inverse range of 52 to 28 per cent, of iron. The manganese costs no more per unit in the ore than the iron, because cost of mining, largely by open-pit methods, is not affected by the manganese content. The manganese units should, perhaps, command a higher price, but as their value is contingent on metallurgical practice, a higher price may be justified only when a shortage in manganese occurs. Manganiferous iron ores can never entirely supplant straight manganese ores though methods are employed that will permit them to do so partly. For the manufacture of ferromanganese, ores carrying above 42 per cent. manganese are needed. Ores with manganese running between 20 and 42 per cent. are used for making spiegeleisen. But established practice in certain plants, based on the admixture of manganiferous iron ores to straight iron ores has greatly lessened the consumption of high-priced, scarce, manganese alloys with good results. The substitution of manganiferous ores for ferro and spiegel affects the manufacture of basic iron and its conversion into basic open-hearth

Jan 1, 1925

By E. G. Woodruff

Few authors of treatises and papers on engineering subjects hare given adequate attention to topographic maps. The statement applies especially to mining engineering in all branches. Even those who have discussed such maps have treated the subject only in a general way. Therefore it is proposed to outline in this paper a few of the uncommon yet important relationships which topographic maps and their by-product, structure-contour maps, have to modern methods of mining investigation and development when the facts depicted on such maps are properly interpreted. Topography, as suggested by the etymology of the word, means a detailed description of particular places. Written descriptions have been found less effective than the pictorial representations, therefore attempts have been made in various ways to picture the surface features of places. Lines and shading have been used, hachures drawn, and, finally, the contour topographic map. To a large extent this style of map is the result of the demands of engineers. It is designed to meet their needs far more than those of the man untrained in engineering. In fact,. the average man obtains a better idea of the topography of an area from the hachure system than from contour maps. Since the maps have been made chiefly for the use of the engineer, they ought to meet his demands on the one hand, and, on the other, should be used by him to the fullest extent. Such maps, when properly made, accurately portray a portion of the earth's surface and should present the topography better than a personal examination of the area without a map could present it, because the person making such examination views only a limited portion of the surface at a time, and estimates distances only roughly with his eye. Let the engineer consider carefully the fact that in many instances the topographic map is superior to a personal examination of the surface features of a property because the map is based on careful instrumental measurements, whereas the eye gives imperfect data because it can be used merely for the estimation and

Jan 1, 1914

By J. R. Thoenen

Six or seven years age the United States Bureau of Nines started development of instruments for the purpose of accurately measuring the vibrational movement of the earth in the vicinity of quarry blasts. V For this work a new type of seismometer has been developod.1/ A number of these have been constructed, the accessory field equipment has been assembled, and approximately 200 field tests of actual quarry blasts have been made. The results of some of these tests have been. published 2/ and others arcs the subject of two manuscripts now in preparation. So far the attention of the investigation has been centered on ascertaining the characteristics and behavior of the ground vibrations. Occasionally, when opportunity Prose, measurements of the vibrations occurring in houses or other structures caused by quarry blasts were made, but without Piny attempt et direct correlation or interpretation. During; 1936 the National Bureau of Standards conducted some experiments to determine the normal vibrations to which the walls and floors of buildings are subject. Cooperation of the Bureau of Mine's was requested in measuring the displace-ment. This afforded an opportunity to study the affect of mechanically induced vibrations end make limited comparison with previous records of vibrations from blasting. This paper duels with the experiments made in cooperation with the Bureau of Standards and includes soma comparisons with affects from quarry shots. The results are in the: nature, of , progress report only, and are not intended to draw definite conclusions. Those, tests were concerned with the determination of the maximum amplitudes of vibration possible in the floors and walls of a typical dwelling when subjected to commonly experienced vibrations. The dwelling tested was obtained by the National Bureau of Standards. It was a large four-story stucco building, 41 ft. south off the southerly curb of Park Road, in. Washington, D.C., which was constructed about 1900 and was supported on overburden. The basement floor elevation was approximately that of the pavement of Park Road. Park Road runs east and west; the front door of the house faced north.

Jan 1, 1937

By J. D. Price, W. M. Bertholf

In preparing a paper on coal washing in Colorado and New Mexico, it is difficult to refrain from entering into a discussion of the historical aspects of this subject, for the story of coal washing in these states goes hack well into the last century. This phase of the subject could well make a complete paper in itself, and of necessity this present discussion must be limited to current operations. Therefore, we are taking into consideration only those washing plants which have operated for some period during the years of 1947 and 1948. Summary Of the eight million tons of coal mined in the two states in 1947. ap- proximately two million tons were washed in wet washing plants, using concentrating tables or jigs. The one table plant accounted for 70 pct of the output of washed coal, and two large Baum jig plants accounted for an additional 26 pct, leaving only a small residual tonnage to be accounted for by other types of jigs The necessity for washing coal is occasioned by the desire or necessity of reducing the ash content of the coals— sulphur is not a problem in this area. All washeries, except the table plant, are at or near the tipple, hence wash only one kind of coal. At the table plant a large number of different coals are washed. Only at the table plant is there any occasion for drying any considerable quantity of fine coal— other plants size and/or dewater on shaking screens. The results of washing at the smaller plants are judged by the number (or lack) of complaints about the quality of the washed coal. This is probably as good a system as can he devised for small, intermittent operations. The efficiency of the Baum jig ap-pears to be quite high. This is to be expected as long as the automatic control of the refuse gate operates properly. The efficiency of the concentrating table is not as high as that of the Baum jig, especially when the "difficulty" of washing is taken into consideration. When dealing with coals in which the "bone" is larger than the "coal," the table appears to be at a definite disadvantage, because of its sizing action.

Jan 1, 1950

By Donald C. Barton

Geophysical methods of prospecting taken as a whole do not seem to offer much promise to a young man planning to enter them in the future. They have come to stay, to be sure, and they will continue in at least moderate use for a long time. Domestic use of those methods presumably is at a maximum at the present time. Geophysical prospecting is expensive; the effects of the law of diminishing returns in efficiency in finding prospects can already be recognized. Small oil companies, independent oil operators, and royalty buyers have been doing much geophysical work. But in face of the increasing costs of discovery of prospects and in face of the probably decreasing favorability of the prospects discovered, I expect to see a sharp drop in their use of geophysics within the next 10 years. The major oil companies and the larger small oil companies will continue to use geophysics indefinitely, but it seems doubtful whether the very extensive domestic campaigns of a few companies will be maintained for many years, certainly not for 10 years. The use of the geophysical methods in foreign countries has not yet reached its peak, and probaby will continue to increase for several years. That peak level of activity will probably be held for 10 years, although the site of maximum activity will shift from country to country; by the end of 25 years from now, I should expect the foreign use of the methods to have leveled off to one-fourth to one-half the peak level. Foreign service in geophysics does not seem to offer an attractive career, except for men of exceptional disposition. Young men just out of college, who are willing and who can afford to spend three or four years having a fling at adventure before settling down, will find it attractive, but when their tour of foreign service is over, they probably will have harder work finding a job than when they were seniors, and their foreign experience will count for little, except for further foreign service. A few men, mainly the higher men, will have headquarters at civilized or semi-civilized cities and towns or at permanent oil-company towns, and can

Jan 1, 1940

By George A. Roberts, Robert F. Mehl

WHEN austenite first forms from aggregates of cementite and ferrite, it is not homogeneous.1 This inhomogeneity, consisting of both undissolved carbide and carbon concentration gradients, has a profound effect upon the characteristics of the austenite-pearlite reaction. The rate of formation of pearlite is increased by the presence of inhomogeneities2,3 and because of this (when the inhomogeneity is sufficiently pronounced) the hardenability of the steel is reduced,4,5 In addition to this kinetic effect, inhomogeneities will cause the direct formation of spheroidite from austenite at temperatures just below the Ae1.6-11 The present report attempts quantitatively to evaluate the effect of inhomogeneity upon the rate of the austenite-pearlite reaction, presents a method of determining the austenitizing cycle necessary to obtain "practical homogenization," and considers the effect of inhomogeneity on hardenability. EFFECT OF INHOMOGENEITIES ON REACTIONS NEAR Ae1 Few quantitative data are available representing the effect of undissolved carbide or of carbon concentration gradients upon the rate of the austenite-pearlite reaction. In procuring such data it is necessary to separate the effect of undissolved carbide from that of grain size, and this is not an easy task. The solution of carbide is always accompanied by an increase in the grain size, both effects contributing to the retardation of the reaction rate. It has been possible to make this separation and to obtain data that are independent of the grain size by the use of steels that differ only with respect to their tendency toward grain-coarsening. Steels C and D in Table I are such steels. These steels have been studied previously;1,2,12 they differ only with respect to deoxidation practice; C was deoxidized with silicon while D, teemed from a portion of the same heat, was deoxidized with additional quantities of aluminum in the mold. C therefore is what is normally termed a "coarse-grained steel" and D is a "fine-grained steel." These steels can be compared at the same grain size by heating C to a low temperature and heating D to an elevated temperature, producing a structure of austenite plus residual carbide in the former while forming homogeneous austenite in the latter; in such

Jan 1, 1943

Primarily, 1961 was a year for widespread application of tools and techniques which have become operational in the past several years • • • Raising --Raise climbers and climber raising techniques have been improved; narrow veins as low as 55° dip are now being mined from climber raises. Climber modifications include: larger motors, tighter radius curves negotiated, improved lubrication and new methods of stowing the climber during a blast. Climber raises are now ventilated in several ways: a 12-in. diam flexible vent tube behind the climber rail; a 6-in. diam pipe behind the climber rail (with fan); or a 6 to 8-in. diam drill hole along the axis of the raise. In hot raises, these ventilating techniques have resulted in more rounds per shift. When driving raises from crosscut and lateral development, mucking machine loading of raise rock is preferred over slusher ramp loading for the following reasons: a) faster set-up and teardown of climber facilities; b) easier access for climber maintenance, repair and loading of raising supplies; c) area at the bottom of the raise can be kept cleaner. Both wide and narrow veins are mined from 7 x 7-ft climber raises at Butte and at Republic, Wash. At Republic, climber rollers have been modified to support increased weight when driving 55°dip raises • Drilling-The new largebore, short-stroke push feed drills are much faster drilling than previous models and are most satisfactory in hard ground. Although reports on maintenance studies of the new drills are not yet available, increased steel and bit wear and breakage, and increased drill maintenance are seen as potential problems. Mines in Montana and Idaho continue to test rubber-collared drill steel. The fabricating methods used are successful but advantages in increased steel life have yet to be proved. Underground applications of down-the-hole drills continue. Drilling speed and accuracy are reported as the outstanding advantages. Manufacturers are now hopeful of making drills which will operate in any direction. Present applications are for ventilation holes (to 8 in. diam) for climber raises, holes for hydraulic fill distribution, drain holes and "predrilled" raises. Good drilling accuracy has been reported to a depth of 200 ft. Cutting holes in drifting is seen as a future application

Jan 2, 1962

By Henry F. Adams, Guy H. Ruggles

In this paper the authors aim to chronicle the experience and salient points brought out in changing flotation reagents at a concentrator which had probably been using a minimum amount of oil at a minimum cost per ton, to a more complicated system requiring a partial chemical control. The original oils were coal tar and pine oil. The new reagents are lime, xanthate and pine oil. It was found that there were no insurmountable difficulties and eventually the cost of the new reagents per ton of ore proved to be very little more than that of the old. Lime Plant When the question of handling lime came up there were two propositions open: (1) to handle the lime dry; (2) to handle it wet in the form of an emulsion. Granting that a dry lime feeder would function properly, delivering lime uniformly, the chief objection was the dust that would be raised when these feeders were being charged or operated, as the only possible location was on a gallery beneath which men were working. With this objection the handling of lime as an emulsion seemed to be the better scheme. The lime plant which was first installed was for experimental work on one section. This was gradually changed and developed until it was of sufficient size to accommodate 20 sections. The various changes will not be discussed and the following description deals only with the fully developed plant. Crude as it is, and perhaps somewhat expensive to operate, the lime-handling plant has been quite successful. Much has been learned which will pave the way for a better installation in the future. Burnt lime is received loose in standard gage box cars. This is the product of the kilns and has had no screening or sorting. A grab sample is taken from each car as it is unloaded. An average of the analyses of samples from 44 cars gave the following: Available CaO Total CaO, Oxide and Hy- MgO, Fe²O³ + Al²O³, Insoluble, Per Cent. drate, Per Cent. Per Cent. Per Cent. Pek Cent. 88.3 79.2 1.6 ' 1.3 2.2

Jan 1, 1928

By G. I. Madden, L. H. Van Vlack

WhEN basic refractories which contain peri-clase, MgO, are used in steel furnaces, they are altered by iron oxide to form magnesiowiistite, (Mg,Fe)O, and an iron-rich magnesioferrite, (Mg,Fe)Fe2O4. Silica, which is usually present, produces a silicate liquid that surrounds the solid phases. The individual crystalline grains of the above two solid phases grow at elevated temperatures. Previous papersL" showed that, if either periclase or magnesiowiistite is present as the only solid phase, its grain size increases in proportion to temperature and in proportion to the square root of time; the growth rate is reduced slightly if the amount of silicate liquid is increased. Similar results have been observed for iron-rich magnesioferrite.3 To determine the effect of the presence of two solid phases on the rate of grain growth, micro-structural studies have been made on samples containing both magnesiowustite and magnesioferrite. The experimental procedure was the same as that followed in the previous studies of this type.'12 Briefly, this included determination of compositions from the available phase relationships4 that would produce the two phases of interest at the firing temperature and using reagent-grade raw materials to prepare mixtures of these compositions. The mixtures were pressed into pellet-size samples and then fired at the desired time and temperature. The samples were water-quenched to preserve the microstructure present at the firing temperature. Standard reflected-light metallographic techniques were used for sample examination and sample analysis. Grain sizes were determined by measuring the mean diameter of a number of randomly selected grains in a two-dimensional microsection. A large cross section of the sample was covered to prevent biased data resulting from such effects as localized differences in the radius of curvature of the crystal grains. Examination indicates that grain growth is restricted when more than one solid phase is present. This is illustrated in Fig. 1 for: (a) magnesiowustite plus a silicate liquid; (b) magnesioferrite plus a silicate liquid; and (c) magnesiowiistite and magnesioferrite plus a silicate liquid. Fig. 2 plots the

Jan 1, 1964

By J. R. Campbell

It is the purpose of this paper to review somewhat in detail the literature on the subject that is extant, which ought to provoke considerable beneficial discussion. The value of 1 per cent. ash in blast-furnace practice was brought to the attention of the writer when he was connected with the U. S. Steel Corpn. Various groups of blast furnaces in the Pittsburgh district compiled a statement in which the average saving was about 6 c. per ton on pig iron for every 1 per cent. of ash reduction. Later, the same groups of furnaces, when materials had reached a higher price, compiled a statement in which there was a 30-cent saving on pig iron for every 4 per cent. ash reduction in the Pittsburgh district, which was equivalent to 7½ c. for every 1 per cent. ash reduction. In the Chicago district, on long freight hauls of coal and coke from the Pocahontas district, the set-up was 30 c. per ton of pig iron for every 2 per cent. ash reduction, or 15 c. for every 1 per cent. Some years ago, Ralph H. Sweetser, of the American Rolling Mill Co., presented a paper which provoked considerable comment.' To get the matter again before this body a résumé of his computations is given below: Comparison of Pig Iron Costs Ash in Coal. Ash in CoKe, Fixed Carbon in Coke peR Ton OB PIG Iron peN Day, Per Cent. PeR CeNt. Coke. Per Cent. PIG IRon. Lb. Tons 6.00 8.70 89.80 1800 365.0 7.00 10.15 88.35 1860 353.2 Coke with 8.70 Per Cent. Ash Ore mixture, 4144 It). = 1.85 tons @ $5.50.............................. $10.17 Coke, 1800 lb. = 0.90 ton @ $6.50..................................... 5.85 Limestone, 1000 lb. = 0.50 ton @ $1.50................................. 0.75 Labor, $365 per day on 365 tons....................................... 1.00 Supplies and service, $250 per day...................................... 0.68 Overhead, $200 per day............................................... 0.55 Reserve for relining and depreciation................................... 1.00 Total............................................................. $20.00

Jan 1, 1931

By L. C. Glenn

In the preparation of this paper the writer has drawn freely upon the writings of Orton, Munn, Shaw, Mather, Miller, Hoeing, St. Clair, Jillson, and others, as well as upon his own personal knowledge of the fields of both states. It is to be regretted that certain data gathered by him and his assistants last fall are not available for publication. Oil in Tennessee A few wells drilled for brine for salt making in Tennessee between 1820 and 1840 obtained oil, but no definite search was made for oil until just after the close of the Civil War. Active drilling was then begun in Overton and counties southwest of it on the eastern half of the Highland Rim. A number of strikes were made at shallow depths in the basal part of the Mississippian but the wells were soon exhausted and abandoned. Drilling was revived, about 1892, when the Spurrier district in Pickett County was developed and was followed by the Riverton district in the same county in 1896. A pipe line was laid from the Wayne County, Ky., fields and about 60,000 bbl. of oil were run before a very heavy slump in the production, a failure to find an extension of the field, and excessive local taxation caused the removal of the pipe line in 1906. There was then no production in Tennessee until the discovery, in 1915, of oil near Oneida, Scott Co., at about 950 ft. (289 m.) in fissures in the Newman or St. Louis limestone. This field, however, soon failed and was abandoned. In 1916, oil was found at Glen Mary, Scott Co., in the Newman limestone at a depth of 1232 ft. (375 m.) A number of wells have since been drilled there, some of which were dry while others, close by, were produccrs. The largest one yielded, at first, about 340 bbl. per day and produced for several months, when it suddenly went dry. Several of the first wells began at 6 or 8 bbl. per day and are still maintaining that output. Production is from a fissured part of the limestone and varies greatly in accordance with the size and extent of the ramification of the

Jan 1, 1921

By Howard Eavenson

The data given in the paper were collected to furnish an idea of the amount required in various operations of bituminous mining to produce a ton of coal, the plants selected being well-managed ones. With these are included some figures compiled from U. S. Coal Commission's report showing the average amount of labor in various classes of mines. THE information contained in the following paper was collected at the request of the U. S. Coal Commission, and is, published with the permission of that body and of the various companies furnishing the data. For obvious reasons, the names of the companies are not given. No data were gotten from States south of Virginia or west of the Mississippi River. The data about the amount of labor, in man-hours, required in producing a ton of bituminous coal have been collected with the idea of showing what is being done at some well-managed plants, and not to show the average amount required by all mines, which undoubtedly is considerably higher than the average of the figures shown.* Almost all of the figures were supplied by the various companies in reply to a questionnaire; when they were obtained from other sources the company was asked to verify them. On account of the amount of work required, the data were only requested for one or two months for each plant, and the figures represent in each case a month when the car supply was good and the work was practically steady. In the case of most of the West Virginia and Kentucky mines, these conditions were best met in May and June, 1922. The mines for which the figures are given are arranged by states and as to whether the mine operates under union or non-union or open-shop conditions. The union mines listed are generally considered to be as well-managed as are the non-union ones. The production per month in a few cases includes the amount of slate which is loaded and hauled out of the mine, as of course this requires nearly as much labor per ton as does the coal. These cases are noted:

Jan 1, 1924

By William A. Edmiston, R. E. Grace

A simplified model for the theory of reaction rates near equilibrium has been applied to the reduction of wustite. A linear relationship between the net rate of reaction and the Gibbs free-energy change, ?F, is predicted. The reduction of wustite in H2 -H2O gas mixtures was studied with a microbalance technique at temperatures from 850° to 950 °C. The predicted model was found to be valid to -?F/RT = 0.1 or approximately -200 cal per mole away from equilibrium. ThE theory of reaction rates near equilibrium has been developed by a number of authors. Prigogine, Outer, and Herbo1 have studied the catalytic hydrogena tion of benzene in an attempt to deduce some intrinsic connection between reaction rates near equilibrium and thermodynamics. Manes, Hofer, and weller2 have derived more general expressions for reaction rates near equilibrium from classical thermodynamics. Hollingsworth3,4 has commented briefly on the work of Manes et al. Benson5 has summarized in a general way the results of the earlier contributions. It is the purpose of this paper to apply the theory of reaction rates near equilibrium specifically to the reduction of wustite in H2-H2O gas mixtures. The basic premise is that the reduction of wustite proceeds by a surface reaction, rather than by solid-state diffusion ,or gaseous diffusion. Richardson and Dancy6 and Gellner and Richardson7 have suggested that the reduction of wustite may be governed by iron diffusion in wustite. Mckewan8-11 has proposed that reduced iron layers on various oxides are sufficiently porous to offer a negligible impedance to the reducing gas. The linear motion of interfaces reported by McKewan and discussed by Themelis and Gauvin12 indicates the lack of diffusive control during reduction. The reduction studies of magnetite reported by Quets, Wadsworth, and Lewis13 give additional evidence that reduction rates are linear when the reaction products are porous and nonprotective. The interpretation of measurements reported in this paper is predicated upon a surface-controlled reduction reaction, at least in the earliest stages of reduction when the reduced iron layer is thin.

Jan 1, 1967