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By C. J. Ramsburg

The construction and operation of by product coke-oven plants in America are essential to strong national defense and of the greatest importance to many widely diversified undertakings as well as to safety and health. Carbonization Process Coal used under a boiler or in a locomotive is consumed by combustion. Coal used in a by-product oven is distilled or carbonized, meaning that heat is applied to the coal, out of contact with air, causing a distillation that removes the volatile matter in the coal in the form of gas and vapor, leaving coke as a final product. From the gas and vapor distilled from the coal, many valuable substances can be secured, known as by-products. Hence the name "by-product oven." The simplest example of this principle can be shown by means of an ordinary clay pipe. If powdered coal is placed in the bowl of the pipe, the opening of the bowl is plugged with clay, and the bowl placed in a flame, the bowl will become hot, transferring the heat through the wall of the bowl to the coal within. When this coal attains a temperature of about 750°F., gas will begin to pour out of the pipe stem, and this gas may be lighted. A black liquid also will exude from the stem of the pipe, This is tar mixed with certain other products. What remains in the bowl after distillation is coke. A coke oven corresponds to the bowl of the pipe. A modern oven of the latest type is a refractory brick chamber approximately 42 ft. long and 14 ft. high, averaging 18 in. in width. The oven is filled with coal through closable charging holes in the oven top. Each end of the oven consists entirely of a self-sealing door, the removal of which permits the finished coke to be discharged by means of a power-operated pusher machine. The ovens are built in batteries, and the heating is effected by gas burned in vertical flues in the oven walls, each set of flues heating the walls of two adjacent ovens. Such ovens carbonize a charge of approximately 18 tons of coal in 18 hr., or have a daily throughput of 24 tons per oven, producing about 17 tons of coke. In times of need, the output may be increased by raising the temperature of flues, thus shortening the coking time. There is one great essential difference in principle between distillation in a clay pipe and in a coke oven. In the 18-in. oven, the distillation proceeds from two parallel walls held at a high temperature (over zooo°F.) and instead of all the coal being heated at once, the distillation is a progressive one creeping inward. The average travel of this heating is 35 in. per hour from each vertical wall, and as the volatile products are formed progressively they must push away from the interior toward the wall through the previously formed hot coke, then up the walls and Over the top of the coal charge, finally escaping through the outlet pipe. This results in a cracking of the components into many different and valuable substances not formed when the carbonizing temperature is low.

Jan 1, 1942

By E. P. Palmatier

RECENTLY a cooling system has been in process of installation on the 3400 and 3600-ft. levels of the Magma copper mine at Superior, Ariz. The general system of ventilation employed at this inclined-vein mine is as follows: Ventilating air enters the shafts on the western side of the mine. Booster fans at each level each deliver approximately 38,000 cu. ft. per 'min. to the drifts. This air passes diagonally upward to the upper levels of the mine on the eastern side, where it passes up the shafts to large exhaust fans on the surface. Owing to the dip of the vein, all operations on the eastern side of the mine are above the 2500-ft. level, and those on the western side below the 2500-ft. level. At present, 2500 lineal feet of new drifts are being driven-on each of the 3400 and 3600 levels. The rock temperature is about 135°F. Until the new installation is completed, ventilating air for the two levels is supplied through Flexoid tubing from small booster fans -on the 3200-ft. level. The air picked up by these booster fans has a dry-bulb temperature of approximately 85°F. and a wet-bulb temperature of 82°F. By the time this air reaches the end of the Flexoid tubing at the 3600-ft. level, the dry-bulb rises to 101°F. and the wet-bulb to 86°F. The conditions at the head of the new drift were 102' dry-bulb and 93' wet-bulb.

Jan 1, 1937

By Clarence Merritt

STAINLESS iron, as mild stainless steel is usually called, an alloy ranging from 11.50 to 15.00 per cent chromium with carbon under 0.12 per cent, has been considered to be not appreciably affected in respect to corrosion resistance by heat treatment. This metal, while one of the most widely used of the "straight" chromium stainless alloys, has failed in many applications because of insufficient information regarding heat treatment. These failures have been attributed to many possible causes from an inherent lack of resistance to corrosion and misapplication to mysterious electrolytic effects or comparatively minute non-metallic inclusions. Many uses for a steel with such excellent physical properties is are latent in this alloy have been lost on account of corrosion failures which could have been avoided by applying proper heat treatment. The alloy has not received the recognition or attention it should because of the fact that' the details of its metallurgical behavior were not thoroughly understood. Response to heat treatment of the steel is well known as regards tensile properties, 1,2 but its application has been for improvement in tensile characteristics or on account of machining considerations rather than for corrosion prevention. The potential user of this steel has not been clearly advised in papers, either technical or commercial, that have been written about it in the last 10 years or more, of particular features that are of prime importance in developing the excellent properties of this metal. The data to be presented in this paper are concerned mainly with the effect of heat treatment on the corrosion resistance, but a study has also been made of the concurrent microstructural changes and an explanation developed for the phenomena revealed, as well as a correlation to the other physical properties-hardness, tensile characteristics and impact strength. Stainless steel, largely used for cutlery purposes, an alloy of approximately 13.00 per cent Cr with 0.30 per cent C, must be hardened and the surface prepared by polishing or pickling for best resistance to staining and corrosion.3 Monypenny reports that a loss of hardness is

Jan 1, 1932

By Thomas L. Garrard, James A. Sprague, Rex B. McLellan, Samuel J. Horowitz

A simple rnodel for interstitial solid solutions has been devised in which each solute atom interacts with the solzlent lattice in such a way as to exclude an integral number of nearest-neighbor sites from being occupied by solute atoms. The vemaining interstitial sites ave not affected. In calculating the entropy of such a solution the increase in the number of interstitial sites available to solute atoms due to the ozlerlap of blocked sites is taken into account. The ther-modynamic functions and the solute activity fov the solution rnodel are calculated. It is shown that considevation of the overlap sues vise to a correction term of the order 8' ( where 0 is the ratio of solute to solvent atoms) in the thevmodynamic functions of the solution and the solute activity. The theo,uetical equation for the solute activity was used to analyze the available data for the activity of carbon in austenite at three different temperatures. The use of a computer enabled many comparisons to be made between the experimental activity data and those predicted by both the complex blocking model and the simple, widely used blocking model in which the ozierlapping of blocked sites is not taken into consideration. Even though at the highest concentvations oj carbon the value of 0 is small it is shown that the best fit to the experimental data is found with the complex blocking model. RECENTLY it has been shown by analysis of gas-solid equilibriums that many interstitial solid solutions can be described by the quasi-regular solution model in which the partial energy of solution E, is independent of composition and, apart from a composition-independent term due to nonconfigurational factors, the partial entropy is that of an ideal solution. Dilute solutions of nitrogen in both bcc and fcc iron,' dilute solutions of oxygen and silver,' carbon in a Fe,' and dilute solutions of carbon in ? Fe2 are all quasi-regular. In addition many hydrogen-metal solutions, both dilute and concentrated (with the notable exceptions of the H-Ni and H-Pd systems), can be described by this model.3 However, it has been shown that, at various temperatures, solutions of carbon in ? Fe begin to depart strongly from quasi-regular behavior at low concentrations. A plot of the activity of carbon in ? Fe relative to pure graphite vs atom fraction of carbon (Cc) calculated from Smith's data4 begins to depart from the (nonlinear) plot for a quasi-regular solution at about Cc = 0.02. Several statistical models have been proposed to account for the thermodynamic behavior of carbon in y Fe. Darken and smith4 set up a model in which a carbon atom in its octahedral site in the fcc lattice has either one or no neighboring carbon atoms in the twelve nearest-neighbor octahedral sites. It is assumed that the number of carbon atoms having more than one nearest neighbor is negligibly small and that a solute atom does not interact with another solute atom located at a greater distance than the first shell of interstitial sites. Thus this model contains two characteristic interaction energies. Darken and Smith showed that this model gives reasonable agreement with the measured variation of carbon activity ac with composition. It is noteworthy that Darken and Smith concluded from their analysis of the activity data using this model that there was a repulsive force between carbon atoms in austenite which reduces the concentration of C-C pairs below that corresponding to random mixing. Recently Aaronson, Domian, and pound5 have considered in detail the statistical model developed by Lachere and by Fowler and Guggenheim7 and have shown that it is compatible with the activity data for carbon in austenite. In Darken's model the energy of solution of carbon in austenite is dependent on temperature and concentration; the departure from Henry's law arises from the concentration dependence of the energy of solution. In Aaronson, Domian, and Pound's discussion of the Lacher, Fowler, Guggenheim model the interaction energy wy between adjacent carbon atoms in austenite is strongly temperature-dependent. Aaronson et al . suggested that this temperature dependence of wy and hence the energy of solution of carbon could be explained either by the formation of clusters of carbon atoms (despite the repulsive nature of wy) or by the dual occupancy of the octahedral and tetrahedral sites by the carbon atoms. However, a temperature-dependent heat of solution

Jan 1, 1968

By A. B. Parsons

LAST YEAR (1934) saw the completion of a ten-year program of reconstruction and modernization of the world's largest lead- smelting plant, that of the ' Broken Hill Associated Smelters Proprietary, at Port Pirie, South Australia, which has a capacity for smelting and refining 220,000 (short) tons of lead per year. It deals with the entire output of lead concentrates from the famous Broken Hill district in Australia, being owned .jointly by the three leading companies: North Broken Hill, Broken Hill South, and the Zinc Corporation. These companies, together with the Sulphide Corporation, are credited with a production of 198,000 tons of lead in 1934. When one says regarding any metallurgical plant that modernization is "completed" he should add "for the moment." Development in the art of metallurgy and in the equipment used never ceases; that which seems close to the last word today is likely to be obsolete in a few years even in a process so well standardized as smelting and refining lead. However, the reconstruction at Port Pirie has altered the procedure materially. More im-

Jan 1, 1935

By A. W. Ambrose

The present plans for the Petroleum Division of the American Insti-tute of Mining and Metallurgical Engineers provide for two principal meetings in the year 1928. The first will be at Tulsa, Okla., in September or October, 1928, with the exact date largely dependent upon the date of the .International Petroleum Exposition. The officers wish to hold the meeting at the same time as the Exposition in order that members of the Petroleum Division of the A. I. M. E. may have the advantage of attending both meetings at the same time. It is planned that this meeting will be devoted largely to petroleum production engineering problems. A tentative outline of subjects to be discussed is as follows: 1. Repressuring New Oil Fields, and naturally in conjunction with this falls Repressuring of Old Fields. 2. Air or Gas Lift. 3. Flow Strings in New Wells. 4. Deep Drilling Technique. It is also planned to have at this meeting a general paper relating to Supply and Demand of Petroleum and its Products. The second meeting is planned for February, 1929, in New York at the same time as the annual meeting of the Institute. Special details have not been carried very far on this meeting, although it is expected the program will cover technical problems in relation to production and refining of crude oil, as well as 1928 development in foreign fields and the United States. It is planned during 1928 to cooperate with the Bureau of Mines in an attempt to compile a set of definitions on petroleum engineering. These would be of value to the petroleum engineering profession, in order to better standardize various terms used in discussion of current problems. It has also been suggested that the Petroleum Division study certain problems in which research work is needed by the petroleum industry and outline certain definite programs that could be carried out by the Bureau of Mines and the U. S. Geological Survey, as a follow-up to

Jan 1, 1928

By C. E. Gregor

Current modern trends in mining show that hoisting shafts are being expected to fulfill an important ventilation function. However, where rigid guides and supporting structures are mandatory, ventilating power costs will be high, unless the transverse structures (shaft sets) are streamlined. In the complex configurations of hoisting shaft furniture patterns, either for original design purposes, or for the adjustment of an existing shaft, a useful degree of aerodynamic optimization, by reduction of overall resistance, can only be effectively evaluated by model studies in a special purpose wind tunnel, as described herein. The author has shown that, in one particular case, an annual power cost saving of more than $50,000 was indicated, mainly by the selection of buntons and dividers of improved aerodynamic profile. Mining companies are now realizing the advantages that can accrue through proper attention to the aerodynamic aspects of mine shaft design. With progressive demands of civilization for an ever greater supply of coal and metals, and with greater depths of working, higher rates of extraction, advanced degrees of mechanization, and improved standards of environmental health and work comfort, shaft design is becoming an extremely important aspect of mining operations. In addition, because the cost of sinking, equipping, maintaining, and operating a mine shaft is continually increasing, there is a greater incentive to use a shaft for the maximum duty, consistent with economy. The current natural tendency is therefore to sink multi-purpose shafts, to install as much equipment as is safely and effectively possible to operate; and then, over and above all these functions, to use the shaft to its maximum possible ventilating capacity, as a major, or auxiliary, airway. Clearly, this latter additional function can only be employed at a significant cost, since the most economic operating airways are smooth-lined and devoid of internal rigid furniture. It is true that hoisting functions can be carried out in such shafts if rope guides are used, but only under restricted conditions. Where a manway must be provided, fixed guides and supporting structures are mandatory, and ventilation costs become accentuated. It is generally recognized that the prime element of cost in ventilating a mine can be represented by the power required to drive the fan unit. It is also known that the largest component of total mine resistance is that of the downcast shaft, where this shaft is equipped with rigid guides for hoisting purposes. The pressure loss varies directly as the resistance of the shaft, in accordance with a modification of the Atkinson equation p = RQ2/3600. Furthermore, the air horsepower drawn is given by the equation AHP = (p x 0/33000. Therefore, the power required to drive the fan unit varies as the resistance of the shaft and the cube of the air quantity. Clearly, if Q is a specified minimum, then the only way to minimize the pressure loss (and the power costs) is to reduce the shaft resistance R. (See Table I for a list of symbols.) The resistance to airflow of a shaft equipped with rigid guides and supporting structural sets consists of two components which, for the sake of analytical simplicity, can be regarded as additive. 1) Frictional resistance, represented by the viscous frictional forces within the boundary layer, as air flows along the surfaces of the walls and the periphery of the vertical elements (guides, pipes, cables, ropes, etc.) of the furniture. The friction loss can be readily calculated by the Atkinson equation, after selection of a suitable value for the friction factor K from the McElroy compilation.' KxLxO xQ2 5.2 xA3 Friction loss can be minimized by lining the shaft walls (particularly if of circular or elliptical cross-section) with a smooth continuous lining of monolithic concrete.

Jan 1, 1968

CHARLES CATLETT, Staunton, Va.-A great many important things have been said in an interesting way but the most startling, to me, is that for 25 years, the price has been in the neighborhood of $1.00, with a minimum of 86 cents and a maximum of about $1.25. It is evident that during all that time the price was inadequate. The amount paid to be divided between the land owner, the capitalist, and the laborer was too limited or too irregular to permit of a healthy condition; yet it is evident that the enormous industrial development of this country was fostered by this very cheap coal, probably the cheapest that has been provided in quantity in any country. I entered the coal business when the price was lowest and my interest and sympathy went out to the man who spent his days in the dirt and foul air of a mine and I was filled with schemes for helping. But at the end of the year, after exercising every economy and in blissful ignorance of proper depreciation and obsolescence, there was still only a profit of 1 cent per long ton for what I think is one of the best coals in the world, the best grade of New River coal. We are now paying a great deal more than we did a few years ago and probably will continue to pay more for some time; but any one who thinks we will not have low prices again is very young or very forgetful. Yet we must have larger profits if the industry is to be healthy, if the three parties to the production are to get adequate returns and be in shape to provide the improvements which will be needed to take the place of and supplement the man-power. This will come when the men are making so much money that the operator wants to replace the man by a machine, and when the operator is making so much money as to be in a shape to make the improvements. He will not put in machinery unless the machinery will save money. We have got to pay a higher prime cost for coal, but engineering skill will teach us how to handle it better and use it more economically, and the ultimate result ought to be of advantage to the public.

Jan 3, 1920

By A. Lucian Walker

SILVER is not only of paramount importance to millions of people as a medium of savings and to other millions as a medium of exchange, but it is also valuable and useful in industry. Mexico continues to be the largest producer of this metal, followed by the United States, Canada, and Peru. The largest consumers are China and India, which normally absorb about two-thirds of the world's mine production, hoarding it as savings. The imports by these countries exert a powerful influence upon the price, yet neither country is on the silver standard. China having abandoned it in 1935 and India in 1893, when the rupee was definitely linked to the pound sterling. Other nations such as Persia, Ethiopia, Mexico, and many of the South American countries either have been on the silver standard or have used silver as their chief circulating medium, and most large nations use it for subsidiary coins, this use accounting for 20 to 30 million ounces annually. The arts and industries have consumed 35 to 40 million ounces each year.

Jan 1, 1937

By P. T. Allsman

INTRODUCTION The honor of being the recipient of the Mining Society's Daniel C. Jackling Award for 1966 imposes on me the responsibility to search for the subject that I would be best qualified to discuss. It seems that my experience in the mineral industry — nearly 15 years in private and 30 years in public employment — should uniquely qualify me to comment upon the relationships between the mining industry, mineral engineering as a profession, and government, and the changing economic, technologic, political and social changes that dictate their relationships. Such conditions, the increasing knowledge of the world mineral resource base, the greater demands of an expanding population with a rising standard of living, shall be evaluated with respect to our profession — mineral engineering. In all of these forty or so years, I have been in close touch with many phases of the mineral and energy resource industries, especially those of the United States. Particularly during the past 10 years, I have had a ringside seat at the "goings on" in Washington. During all of this period I have observed and analyzed many of the problems of the industry and its relations with the government. During the past few years, I have had increased opportunity for doing research and have found a need to learn something about the mathematical techniques that are undergoing such a revival since electronic computers were developed. One of these techniques is multivariate analysis, which is a system for correlating a large number of complex variables. By applying this technique to the seemingly chaotic present-day situation, there emerges a course of steady improvement in the minerals resource industries that wars, depressions, and political strife have failed to obstruct for long. In short, I advocate a need for new concepts in mineral engineering to cope with the changes, pos- sibly adding many more specialized areas on one end of the spectrum, and broad engineer-generalist approaches at the other. The meeting place shall be where the intricate mineral resource problems at the frontier of knowledge merge into the socio-techno-logical problems of the world. HISTORICAL INVOLVEMENT OF GOVERNMENT IN MINERAL RESOURCE PROBLEMS Involvement of government in mineral resource problems undoubtedly is as old as government itself. But passage of the Mining Act of 1866, superseded by the Act of 1872, was the first major entry of our Federal Government into the problems of mining. Passage of the law was necessary to resolve many conflicting claims and disputes in mining. The General Mining Law of 1872 and the Mineral Leasing Laws of 1920 apply to millions of acres of public lands and to certain privately owned land on which the mineral rights have been reserved to the Federal Government. The extensive involvement of government in the mineral industry business today often comes as a shock to the mineral engineer who has begun to climb the ladder to the top in his company. He is often poorly prepared to cope with the situation and becomes frustrated and even hostile. Better knowledge of the role of government perhaps would ease his situation. In our political system, private industry is responsible for producing minerals. To make certain that the production is adequate for a peace-time economy, and to guarantee the Nation's security in an emergency, the Federal Government finds it expedient to develop policy and engage in regulatory, educational, and research activities. A few examples will illustrate the varied role of government in relation to mineral problems. In varying degrees many agencies of the Executive Branch of Government have responsibilities that influence the functioning of the mineral and energy industries. In addition, of course, Congress, the Judiciary, and State and local governments exercise great influence. The Department of the Interior is primarily responsible for activities to promote the development and conservation of mineral and fuel resources, and the

Jan 1, 1967

By Clarence G. Merritt

Stainless iron, as mild stainless steel is usually called, an alloy ranging from 11.50 to 15.00 per cent chromium with carbon under 0.12 per cent, has been considered to be not appreciably affected in respect to corrosion resistance by heat treatment. This metal, while one of the most widely used of the "straight" chromium stainless alloys, has failed in many applications because of insufficient information regarding heat treatment. These failures have been attributed to many possible causes from an inherent lack of resistance to corrosion and misapplication to mlysterious electrolytic effects or comparatively minute non metallic inclusions. Many uses for a steel with such excellent physical properties as are latent in this alloy have been lost on account of corrosion failures which could have been avoided by applying proper heat treatment. The alloy has not received the recognition or attention it should because of the fact that the details of its metallurgical behavior were not thoroughly understood. Response to heat treatment of the steel is well known as regards tensile properties,1-2 but its application has been for improvement in tensile characteristics or on account of machining considerations rather than for corrosion prevention. The potential user of this steel has not been clearly advised in papers, either technical or commercial, that have been written about it in the last 10 years or more, of particular features that are of prime importance in developing the excellent properties of this metal. The data to be presented in this paper are concerned mainly with the effect of heat treatment on the corrosion resistance, but a study has also been made of the concurrent microstructural changes and an explanation developed for the phenomena revealed, as well as a correlation to the other physical properties—hardness, tensile characteristics and impact strength. Stainless steel, largely used for cutlery purposes, an alloy of approximately 13.00 per cent Cr with 0.30 per cent C;, must be hardened and the surface prepared by polishing or pickling for best resistance to staining and corrosion. Monypenny reports that a loss of hardness is

Jan 1, 1932

By B. F. Fackenthal

One of the practical questions presented to the blast-furnace manager, with regard to which little help can be obtained from existing technical literature, is the manner of filling and blowing-in. This operation is often performed according, more or less, to traditions which have come down from earlier practice, and which, if not positively detrimental when followed with the large modern furnace, may at least be greatly improved, just as the running of the furnace itself, while in blast, has been improved. It is not necessary, as many of the old furnace-men believed, to make a lot of white or silver-gray iron at the start, or to spend many weeks, or months even, in bringing the furnace to its normal burden. It has seemed to me that the publication of carefully-recorded data of practice on this point may be interesting to the members of the Institute engaged in the management of blast-furnaces. The enlarged blast-furnace at the Durham Iron Works, Riegelsville, Pa., owned by Messrs. Cooper & Hewitt, of New York City, was first put in blast February 21, 1876, since which time it has made seven blasts, and is now running on the eighth. A description of the furnace-plant, together with a record of the fifth blast, was given in my paper read at the Chattanooga meeting, May, 1885 (Transactions, xiv., 130). After some of the early blasts the furnace-lines underwent considerable change, and I have thought best to accompany this paper with drawings showing the lines and the tuyere-arrangement (see Plates I. and II.), and to give also the following summary of the conditions and results of each blast. During the first and second blasts no coke was used, and the furnace ran very irregularly, showing a constant tendency to scaffold, which was attributed, in great part, to the small hearth and other defective lines. The large proportion of air required at this furnace is accounted for by the fact that the engines are defective, and do not deliver into the furnace the amount of air indicated by the pistondisplacement.

Jan 1, 1890

By E. H. Mohr

AT the McGill concentrator of the Nevada Consolidated Copper Co., all flotation operations have been carried out in Forrester cells since November, 1926. In respect to cost of operation, the new cell has proved to be superior to the Callow, which it supplanted, and its incorporation in the flow sheet has resulted in a marked improvement in the metallurgy. Before citing the advantages of the new machine over the old, it should be explained that the Forrester has not only replaced the Callow, but it has made possible the elimination of a number of tables as well. When Callow cells were in use, table concentration preceded flotation. The ball mill pulp was elevated, by means of air lifts, to roughing Wilfley tables situated two floors directly above the flotation floor. On an intermediate floor were additional tables which cleaned the concentrate from those above. The finished table concentrate constituted approximately 60 per cent. of the total mill production, and contained about 40 per cent. of the recovered copper. The table tailings were returned to the classifiers, the overflow from which went to the flotation cells and the oversize to the ball mills. As soon as the Forrester cells were installed, this tabling operation was discontinued. The ball mill pulp now discharges into the classifiers direct, without the intermediate tabling. It was impracticable to employ the present flow sheet when Callow cells were in use, for the reason that unless the greater part of the heavy mineral was first removed, it accumulated on the mats and adversely affected the flotation operation. By tabling ahead of flotation, it was practicable to maintain the concentrator at 10 to 20 per cent. greater capacity (depending upon the pyrite content of the ore) than was possible by flotation alone. This was due to the necessity for finer grinding in the latter case. Even though the table concentrates contained only 6 to 8 per cent. copper content, the low smelting costs made it advantageous to operate at high mill capacity, at the cost of low grade of product.

Jan 1, 1927

By Stefan Boshkov, Malcolm T. Wane

THE validity and accuracy of velocity measurements underground have been questioned repeatedly by those in mine ventilation work. The general disagreement on the subject is well illustrated in an AIME publication.' Although the presence of errors is readily admitted, their magnitudes are not known and often are described by practical operators merely as "great," "small," or "of no importance." The belief that errors are of academic interest only prevails because of a justifiable claim that actual volumes of air circulated are well in excess of those required by law and safe mining practices. Poor understanding of the source and nature of errors inherent in velocity measurements, coupled with questionable determination of cross-sectional area, result in faulty techniques for the purpose of expediting ventilation surveys and render doubtful the calculated volume. Often consistency of readings is confused with accuracy. A succession of check readings showing a maximum deviation of 5 pct in the measured value of velocity usually signifies nothing more than diligent application of technique in a stable ventilating current. This article discusses the errors involved in air measurements underground. Where instrument errors are presented, the treatment is confined solely to the rotating-vane anemometer, recognized as a most useful ventilation measurement tool because of its simple design and easy operation. In the following pages a positive deviation is defined as one which has to be added to the registered air velocity to obtain the true air velocity.

Jan 1, 1956

By A. H. Lindley, Fraizer M. Stewart

For many years large mining companies were able to finance nearly all of their capital requirements from internally generated funds. However, during the last decade, funds needed for capital expenditures, dividends, and scheduled debt retirement have grown faster than cash flow. As a result the minerals industry has had to rely increasingly on other sources of funds. Getting the capital for new mining projects is a challenge, particularly for smaller companies. New methods of financing and new variations to old methods have been developed and more are needed. Commercial banks are short-term lenders. By policy their loans are limited to low risk loans-those made solely on the borrower's general credit, and secured loans where cash flow is sufficient to provide repayment within a comparatively short term. To maintain liquidity, banks prefer to make loans of less than seven years' term. If a longer loan is needed an insurance company or pension trust may take the long-term part.

Jan 1, 1971

By NEWTON B. KNOX

THE Guianas region is a geological unit, consisting of the northern lobe of the Brazilian Shield, but political accident and the fact that rivers act as the principal means of transportation have divided the region between five separate sovereignties. Brazilian and Venezuelan Guiana have already been considered. The French, Dutch, and British colonies consist of a coastal plain some fifty miles wide, which, together with the lower reaches of the principal rivers, support the greater part of the population. Inland from this tidewater region is a wide area of low, forest-covered hills, under-lain by gneisses, schists, granites, and pegmatites of the Shield. As in Venezuelan Guiana, these rocks are overlain by a thick series of horizontal continental sediments intruded by moderately basic magmas. Gold, bauxite and diamonds have been the principal products of the colonies. The first metal is quite widespread in the hill country. The quartz mines are small, though occasionally rich; probably the greater number of veins remain undiscovered because of the thick mantle of decomposition product that covers the schists and gneisses. The greater proportion of the gold, therefore, is derived from placers which are exploited in all three colonies. Some geologists claim that they occur in two belts parallel to the coast; whether this feature has its origin in the location of the primary mineralization or in the gradients of the rivers is not clear. In some instances the river gravels grade into auriferous laterite. The laterites are well developed in the Guianas and represent the weathering products of the more basic rocks.

Jan 1, 1946

By C. E. Lundin

The Ce-H system was investigated in the temperature range, 573° to 1023°K, and the pressure range, 10-3 to 630 Torr, as a function of 'composition up to 72 at. pct H. Families of isothermal arid isopleth curves were plotted from the pressure-terr~perature-composition relationships. From these curves the solubility relationships were determined for the system. The isopleths are analytically represented by equilibrium dissociation pressure equations. The relative partial molal enthalpzes and entropies of solution of hydvogen in the systerrz were calculated fronz the dissociation pressure equulions and are tabulated. The integral free energies, enthalpies, and entropies of mixing in the Ce-H system were determined from the relative partial quantities and are also tabulated. The standard free energy, enthelpy, and entvopy of reaction of the dihydride phase at kcal per kcal per mole H2, and ?S° = -34. 1 cal per deg mole H2, respectively. The equilibrium dissociation pressure equation in the two-phase region is: UNTIL recently very little was known of the detailed solubility and thermodynamic relationships of the Ce-H system. Two previous investigations1,2 are noteworthy. However, significant discrepancies and omissions exist on analyzing them. The work of Mulford and Holley1 on cerium did not clearly delineate the boundaries of the two-phase region, Cess - CeH2-x. The plateau partial pressures were not thoroughly defined and were considerably displaced in pressure compared to those from the work of Warf and Korst.2 These latter authors concentrated their studies primarily from 823° to 1023°K in the pressure range of 1 to 760 Torr. No data were determined to outline the regions of primary solid solubility and the hydride phase. Also the establishment of the plateau partial pressures was rather limited in scope. In neither work was a treatment conducted of the relative partial molal enthalpies and entropies of solution of hydrogen in the single-phase regions and the integral thermodynamic quantities of mixing throughout the system. Therefore, it was the objective of this research to determine the complete equilibrium solubility relationships and thermodynamic data for the system by pressure-temperature-composition studies. EXPERIMENTAL PROCEDURE The cerium metal for this study was donated by the Reno Metallurgy Research Center of the Bureau of Mines. Total impurity content was 0.13 pct with only 60 ppm O. The metal was checked metallographically and contained only minor amounts of second phase compared to cerium from other sources. Specimen preparation was done in a dry box flushed with argon gas. The surface of a small rectangular piece of cerium (about 0.2 g) was filed with a clean, mill file. Final weighing was done in a tared enclosed vial containing argon gas. The specimen was then loaded quickly into the reaction chamber which was purged several times with high-purity hydrogen gas and then allowed to pump to about 10-6 Torr. The furnace was heated to the reaction temperature and the run started. The equipment used to conduct the hydriding was a Sievert's-type apparatus. Basically it consisted of a source for pure hydrogen, a precision gas-measuring burette, a heated reaction chamber, a McLeod gage, and a mercury manometer. Pure hydrogen was supplied by the thermal decomposition of uranium hydride. The 100-ml precision gas burette was graduated to 0.1-ml divisions and was used to measure the quantity of gas and admit it to the chamber. The reaction chamber was a quartz tube. Prior to each run, the cerium specimen was wrapped in a tungsten foil capsule to prevent reaction of the cerium with the quartz. Control of the temperature was achieved within ±1°K. Pressures in the manometer range were measured to ±0.5 Torr and in the McLeod range (10-3 to 5 Torr) to ±3 pct. The compositions of hydrogen in cerium were calculated in terms of hydrogen to cerium atomic ratio. These compositions were estimated to be ±0.01 H/Ce ratio. The technique used to study the equilibrium pressure-temperature-composition relationships of the Ce-H system was to develop experimentally a family of isothermal curves of composition vs pressure. The range of pressure through which each isotherm was developed was from 10-9 to about 630 Torr in the temperature interval, 573° to 1023°K. RESULTS AND DISCUSSION The hydriding characteristics of cerium are iso-morphous with those of the elements of the light-rare-earth group (lanthanum, cerium, praseodymium, and neodymium) wherein the region from the dihydride to trihydride is continuously single phase.' The structure of this phase is fcc.3 The heavy rare earths form a trihydride,2 which is hcp, separated by a two-phase region from the fcc dihydride phase. The Ce-H system is represented by the family of experimental isotherms in Fig. 1. Due to the small scale required to draw the curves, the experimental points are omitted; however, a total of 240 experimental data points were taken to prepare these curves. The solubility relationships can be deduced therefrom. Three distinct regions of partial pressure and composition can be seen. The region of cerium solid solution is represented by the rapidly rising isotherms in the dilute composition range. In accordance with Gibbs Phase Rule only one solid phase, the cerium solid so-

Jan 1, 1967

By Ta M. Li

Recent start-up of the Pinto Valley mine and mill is expected to add to domestic copper mine capacity by some 62,500 tpy. Owned and operated by Cities Service Co.'s Miami Operations, the complex lies approximately 5% miles west of Miami, Ariz. The estimated $100- million project, the largest single construction project ever undertaken by Cities Service, includes the Pinto Valley open pit mine, a 40,000-tpd concentrator, and a 10-mile slurry pipeline that will transport a 28% copper concentrate slurry to a new filter plant located in Miami. Concentrate will be treated nearby at Inspiration Consolidated Copper Co.'s new smelter complex. The current pit design contains reserves of approximately 350 million tons of ore averaging 0.44% Cu. Based on an initial production target of 40,000 tpd ore and 60,000 tpd waste, mine life is estimated at 24 years. The current stripping ratio is 1.5: 1, requiring the ultimate removal of more than 500 million tons of waste and leach-grade material.

Jan 6, 1975

By W. E. Rice

THE ceramic industry has to do with forming or molding articles of clay, and imparting to them their characteristic properties of permanence, strength and color by subjecting them to heat treatment in kilns. This heat treatment is commonly known as "firing" or "burning." The art of firing clay ware antedates the industrial use of coal; hence wood was the fuel first used, and the earliest kilns were built to burn wood. The majority of the clay ware produced today is fired in periodic kilns that are essentially enlarged structures similar to the earliest enclosed kilns; a kiln consists of a large chamber 16 to 32 ft. dia. (or rectangular) in which the ware is charged and fired either in direct contact with flame or hot gases from the fuel, or in saggers which shield the ware from direct contact with the gases. The fuel is burned in a number of small furnaces built in the thick .wall that encloses the chamber; these furnaces are from 16 to 36 in. wide and from 3 to 5 ft. long; some of them have horizontal or sloping grates, but many have no, grates; the last are called "dead-bottom" furnaces. The temperature necessary to mature the charge in the kiln varies for different clays; for some it is as low as 1800°, and for others as high as 2700° F. Wood was an ideal fuel for the low temperatures that were used in early kilns; it burns freely and produces along, clean flame, which promotes uniform distribution of the heat in the kiln; it does not coke and so restrict the passage of air through the fuel bed; the ash does not melt in the fuel bed to form clinker; and the ash that is carried into the chamber and deposited on the charge does not contain iron and sulfur to discolor the clay. The extent of the ceramic industry now precludes the general use of wood in kilns, so that today this industry is one of the large users -of bituminous coal, burning more than eight million tons annually in kilns. Manufacturing plants usually are at or near the source of clay, with deposits of coal suitable for kilns occurring near the clay. The cost of coal is the largest single item of expense in the manufacture of clay ware, and, because all coals are not equally suitable for the process, the careful selection of coal is important. In this selection the desidera-

Jan 1, 1932

By Sam Tour

SOME years ago, the writer described heat checks or thermal cracks that occur in die-casting dies.1 The life of dies was considered in relation to the casting temperature, the material used for the die, and the heat to be absorbed by the die per unit volume of casting made. The mech-anism of the action that results in thermal failure of dies was described. In the present paper the writer proposes to describe some additional observations in regard to heat checking, make one or two suggestions as to the method or methods for further attack of the problem, and give the results obtained on some work carried out along these lines.

Jan 1, 1934