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By George Mah, Charles Wert

Internal-friction peaks caused by diffusion of oxygen and nitrogen have been observed in ytterbium. They are thought to be caused by the redistribution, under stress, of strain dipoles around an interstitial oxygen or nitrogen and a neighboring substitutional impurity. With the use of a simple geometrical model, diffusion coefficients for oxygen and nitrogen between special interstitial sites have been calculated. a) APPLICATION OF INTERNAL FRICTION TO MEASUREMENT OF DIFFUSION RATES IN DISSOLVED INTERSTITIAL ATOMS In bcc metals, the interstitial atoms occupy the centers of cube faces (0, 1/2, 1/2), or their equivalents, the center of the cube edges (0, 0, 1/2). An interstitial atom in this position causes an aniso-tropic distortion in the lattice. When stress is applied, mechanical relaxation can take place by the movements of the interstitial atoms. This relaxation has been used to obtain information concerning the movements of the interstitial atoms in the bcc metals. Data for these alloys have been compiled by Stanley and Wert. Other researchers have extended the investigation of interstitial diffusion to the close-packed metals. Gupta and weinig2 found an oxygen peak in a titanium, the height of which is linearly dependent on the oxygen concentration. They assumed, therefore, that they were dealing with movement of atomic ally dispersed oxygen in titanium. KG and wang3 determined that the diffusion coefficients of carbon in fcc steels and in nickel obtained by internal-friction methods were consistent with those obtained by macrodiffusion methods at much higher temperatures. Bisogni found oxygen and nitrogen peaks in hafnium by use of which he deduced the diffusion coefficient of these gases in hafnium. He observed further that the half-widths of these peaks corresponded almost exactly with those of a single-relaxation process; he assumed it to be caused by movement of atomically dispersed oxygen and nitrogen. From these studies, the deduction can be drawn that, in general, diffusion data can also be obtained for the interstitial diffusion in close-packed metals (or more precisely, in slightly impure close-packed metals). One group of such metals for which little data exist for the diffusion of dissolved oxygen and nitrogen is the rare earths. They have great affinity for gases, which enter solution interstitially. In this investigation results were obtained for the Yb-O and Yb-N interstitial solid solutions with traces of substitutional impurities; these solid solutions are of fcc structure. b) MECHANISM OF THE RELAXATION IN FCC CRYSTALS In the fcc structure, an interstitial gas atom is usually situated in the octahedral position (1/2, 1/2,

Jan 1, 1964

As 1970 develops and industrial minerals stand at a crucial point in their progress, research and development programs appear to be the key needed to open up new uses for each mineral's future growth. Radically new processes are needed for making a host of new synthetic products from mineral raw materials which will more nearly meet the demanding specifications required for high performance in space, nuclear and defense applications. Consumer applications for high temperature environments will be needed and are important for continuing the nations economic mineral position. In addition, an acute materials problem limits the effectiveness of some of the newer concepts for controlling ail pollution. What is needed then, according to a report printed by the National Academy of Sciences, is the carefully planned development of a limited number of major centers at universities to provide for both basic research and training of personnel; the nurturing of interdisciplinary mechanisms for research and problem solving within these centers; the achieving of a better balance between physics and chemistry within research, emphasizing the chemical aspects of the material sciences; and the enhancement of a broader professional identity by unifying the various disciplines involved into a possible federation of existing societies which have an interest in the problems. [EE] presents its 1969 annual industrial minerals review, where individual authors evaluate the status of each industrial mineral and recount the major developments which occurred during the year.

Jan 1, 1970

By E. J. Hall

(Butte Meeting, August, 1913.) THE iron-nail method of assaying has been used for a number of years, but has not met with the approval of all assayers. The method possesses advantages which may be given as follows : (1) no preliminary treatment is required ; (2) a lead button of proper size can be obtained (3) it is economical. On, the other hand, it has its disadvantages, which may be summed up as follows: (1) it is not applicable to ores containing large amounts of impurities other than sulphur, as practically all the base metals will contaminate the lead button ; (2) the slag is unsatisfactory in the larger number of fusions; (3) the method was known to give low silver results under certain conditions and the gold results were questionable. It was with the idea of determining the extent of this latter disadvantage that the following investigation was undertaken. It is well known that the fusion obtained in the lend assay is far more satisfactory than that in the " nails method " for gold and silver. The principal difference in the charges as a class is the presence of considerable reducing agent in the lead charge, and a limited oxidizing action in the nails charge, due to PbO. The possibility of improving the nails fusion by simulating the lead charge was the reason for using argol in some tests, even though there were reasons for expecting this would have -au objectionable effect on the results.

Jan 6, 1913

By A. G. Rozner

TRANSVERSE rupture tests have been commonly used in mechanical investigations of brittle materials. The specimens are simple, easy to prepare, and loading presents no difficulty. Owing to the complexity of stress distribution in bending1 one can determine stresses rigorously only for the elastic range. The bend-test results, however, are at times converted into tensile-strength data, determined as maximum fiber stress. The assumption is made that for small plastic deformations the linear stress-strain relation applies. This problem was experimentally investigated by Bach3 who tested cast iron in bending and in tension and found that the maximum fiber strength obtained in bending exceeded the experimental tensile strength by a factor depending on the geometry of the tested piece. The factor varied from 1.57 for a rectangular cross section to 2.12 for a circular cross section of the tested beam. Since this work was carried out 60 years ago, the cast iron used could be expected to have been highly brittle, thus the extent of plastic deformation prior to fracture very small. We have therefore carried out a number of tests on magnesium-modified cast iron with an average elongation of -5 pct. It was hoped that the data obtained from the tests would serve as a guideline for comparing data obtained in tension and bending for brittle materials. Mechanical properties were measured at room temperature on an Instron tensile machine at a crosshead speed of 0.05 in. per min. The three-point bend test employed cylindrical bars 0.20 in. in diameter with a 1.0-in. span. For the tensile test, cylindrical tensile specimens with a gage length of 0.85 in. and a diameter of 0.160 in. were used. Results are summarized in Table I. From Table I one can see that fracture strength

Jan 1, 1965

By R. W. D. Clarke, J. C. Folinsbee

INTRODUCTION This paper deals with a procedure for planning the mining of an orebody for which cross-sections, plans, grade of ore, and a geological estimate of the ore reserve have been prepared. The procedure begins with the preliminary selection of a mining method or methods on which an engineering evaluation will be carried out. The engineering evaluation is described in three parts: Conceptual Studies Engineering Studies Detailed Design An overall planning model is presented, plus an expanded model for the Engineering Study Throughout the discussion of the planning procedure, reference is made to three bulk mining methods, including block caving, sublevel caving, and longhole sublevel stoping, including a summary of the main characteristics of each of these mining methods. The planning model is designed for a longhole sublevel stoping method, but with modification, will apply to other methods. PRELIMINARY SELECTION OF A MINING METHOD To experienced mining engineers, identification of the nominal mining method for a given orebody normally involves a large measure of judgement. The geological data is reviewed to determine the configuration of the orebody, including size, shape, dip, grade, and metal distribution. Geotechnical data is considered, including the competence of the ore and host rock, faults, fracture patterns, groundwater, and the potential for in situ stresses. Geographical data, including the natural and societal conditions, are evaluated for their effect upon the mining method, and finally, economic data, basically defined as the value of the ore in the ground, but more specifically, including grade of mineable ore, distribution of ore grade throughout the orebody, and metallurgical recovery, will have a bearing on the nominal method selected. Preliminary evaluation of these factors will result in the elimination of the obviously inappropriate mining methods, leaving some method or methods for further, more detailed study. Since ore does not occur in simple geometric shapes, the method selected for more detailed study will require some variation to the standard. A few key factors will bear heavily on the selection and provide a basis for the most realistic choice. Geological Data The configuration of an orebody defined by the horizontal and vertical dimensions, the dip and strike, and the possibility of repetitive occurrences will have the major influence on the selection of the mining method. For bulk mining methods, the dip of the orebody should be steep, or the orebody must be thick so that gravity can be utilized to deliver fragmented ore to a central gathering area. Geotechnical Data The geotechnical data will be studied in greater detail when the nominal mining method has been selected and the engineering evaluation is undertaken. However, some basic initial information must be available. The structural strength of the ore and host rock, including the effect on it of faulting, fracturing, and insitu stresses, must be known. Data from exploration drilling and examination of drill core will assist in the preliminary assessment of these factors. Highly fractured ground may suggest a caving method of mining for certain orebody configurations, whereas highly competent or strong ore might indicate that for a similar configuration, longhole sublevel stoping will more likely succeed. Data obtained on groundwater from exploration drilling will be considered to determine if it can be controlled, or if it will represent a long term major expense or a hazard for which no control is possible.

Jan 1, 1981

By CHARLES HOPPER

In preparing the Steep Rock Lake iron ore body for mining, it was necessary to drain Steep Rock Lake. Using diamond drills, a cut 1800 ft long, 100 ft wide, and maximum depth of 95 ft amounting to 300,000 cu yd of material, was excavated in Greenstone to provide a drainage channel. This was done under the general contractor C. A. Pitts, of Toronto, who in turn employed a diamond drill contractor, Boyles Bros., to do the drilling. The method of excavation was selected be- cause a clean square cut and grade could be maintained in the bottom of the channel. Bootlegged holes would have left blocks of rock in the corners which would have created a situation which would have become progressively worse as the open cut advanced from one side of the ridge to the other.

Jan 1, 1949

By F. W. Aul, R. C. Glenn

EXTRACTION techniques are of particular importance in determining size, shape an: crystal structure of particles smaller than l000Å in steels and other alloys. However, artifacts that can arise during the preparation of extraction replicas may lead to erroneous conclusions. The purpose of this note is to illustrate some of these artifacts and the misinformation that can result from their presence. An alloy of iron with 0.8 pct Cu was investigated in the following conditions: 1) Solution treated 3 days at 925°C in dry hydrogen and quenched in water. Aged in steps to precipitate copper, as follows: heated to 700°C, held 1 day; then furnace cooled to 50O°C, held 3 days; then furnace cooled to room temperature. 2) Solution treated 3 days at 925OC in dry hydrogen and furnace cooled to room temperature. 3) Solution treated 3 days at 925OC or 17 hr at 1100°C in dry hydrogen to dissolve all copper, then quenched in water. A normal parlodion dry-extraction technique was employed after etching the specimens with super picralP or with 2 pct nital. A wet-extraction method

Jan 1, 1962

By J. E. Lawrence

Copper-decorated lattice disorders in silicon have been analyzed by electron transmission microscopy, chemical etching, and P-N junction reverse current measurements before and following different gettering treatments. Lattice disorders acted as the nucleating sites for copper precipitation. Copper precipitates in silicon resist chemical etching, absorb electron beams more than silicon, and cause excess reverse currents. Totally gettered disorders will chemically etch rapidly, be transparent to electron beams at extinction contrast, and not contribute to excess reverse currents. Three different gettering procedures were performed to determine the effectiveness of different EXTRANEOUS metal contamination can alter the minority carrier lifetime and resistivity of bulk silicon as well as cause excessive reverse currents in semiconductor devices. Previous workers have reported such activity for gold,1,2 copper,'-* iron,' and rnanganese.2,5 Gettering is a method employed to render these impurities electrically inactive. However, some property of the junction-degrading metals prevents gettering procedures from being wholly reliable. The comparative effectiveness of gettering with different agents has been the topic of earlier publications.2,3,6-11 Two mechanisms for gettering metallic impurities have been proposed: the distribution coefficient mechanism by Thurmond and Logan7 and the compound formation mechanism by Goetzberger and Shockley.2 Both of these models evolved from data gettering mechanisms. First, phosphorus was allowed to enter a protective SiO2 film but remain away from the Si-SiO2 interface to test the effectiveness of the compound formation gettering mechanism. Second, phosphorus was allowed to enter the backside of silicon wafers to test the effectiveness of the lattice strain gettering mechanism. Finally, nickel was diffused into the backside of silicon wafers to test the effectiveness of the distribution coefficient gettering mechanism. In each case, copper precipitates dissolved as a result of the gettering treatment. Tightly packed precipitates will resist gettering more than loosely packed copper precipitates. acquired by the electrical analyses of gettered semiconductor materials. An electrical analysis, however, cannot identify the fate of the gettered metals. The radiotracer technique has recently been applied to determine the redistribution of metals following different gettering treatments.3,9,10 The spatial resolu tion of the radiotracer technique prevented the analysis of metal precipitates which contribute to the excessive reverse currents of P-N junctions. The gettering processes employed by the earlier workers, almost without exception, allowed the gettering agent to enter the silicon lattice. This procedure makes it quite difficult to differentiate between the distribution coefficient and the compound formation mechanisms. The metallographic analysis of gettered copper precipitates discussed in this work supplements the earlier work by obtaining direct evidence of silicon lattice defects decorated with copper before and following different gettering treatments. The effectiveness of a process which restricts the gettering agent, phosphorus, to a dielectric film and thus away from the silicon lattice is discussed in addition to the ef-

Jan 1, 1969

By John W. Cabot

The fact has long been known, that the temperature at which steel is made and cast bears a very important relation to the molecular condition of the cast ingot. But until quite recently this fact has not received the consideration which its importance seems to justify. That the ingots from a very " hot " blow in the Bessemer converter, for instance, would not roll as well as those made at a lower temperature, was observed very early in the development of the process; but the further investigation of the effects of varying temperature from "hot" to "cold," has not been carried out with that degree of fulness which has been accorded to the effects on the rolling of the chemical elements, and other conditions in the manufacture. In the following pages will be presented the results of an investigation of this subject, undertaken with the view of determining how far the influence of temperature extends, through how great a range its effects can be traced, and what temperature in the making and casting will give the best results in the rolling of the ingots. In the series of observations forming the basis for the conclusions arrived at, while it was not possible to get the full chemical analysis of every heat considered, a complete record of each, in other details, was made, and a large number of these were averaged together to

Jan 1, 1886

By John J. Sense

The Mission unit of the American Smelting and Refining Co., located 20 miles south of Tucson, Ariz., is a high-volume, 15,000 tpd operation which utilizes a relatively light equipment fleet. As such, management is very conscious of the mechanical and operational availability of the equipment in use. One of the key items in attaining this efficiency is a complete and reliable record of mechanical and operational machine availability which is an invaluable guide for: 1) Estimating future equipment and personnel requirements of an operating property. 2) Planning an expansion program of an operating property. 3) Estimating equipment and personnel requirements of a new property. 4) Selection of replacement equipment. 5) Comparison of separate operating properties.

Jan 3, 1964

By S. W. Parr

FRom a study of sulfur with reference to its specific combination in coal, published as University of Illinois Bulletin No. 111, 1919, it is now possible to determine the various forms of this constituent with a good degree of accuracy. This fact suggests two questions: (1) Are the same analytic methods applicable to coke? (2) Is there any correlation between the forms of sulfur as it occurs in coal and the residual sulfur found in the finished coke? The answer to the second question might be helpful in answering a still further question as to what chemical route the sulfur travels during the carbonization process. While the special studies along these several lines are by no means complete, a few preliminary statements are herewith presented. They may, at least, prove suggestive of further possibilities from a continuation of research along these lines. There is no reason, chemically, why the analytic methods devised for coal should not apply to coke and a fair amount of experience in connection with such use affords confirmation of this statement. The procedure in the case of coal may be briefly outlined as follows: Combinations of sulfur as sulfate, or sulfides other than FeS2, are readily dissolved without disturbing either the pyrite sulfur or the sulfur that is in organic combination by means of dilute hydrochloric acid— 1 part of concentrated HC1 to 10 parts of water or approximately 3 per cent. acid. Digestion at 60" C. for 24 hr. insures the complete removal of the sulfur thus combined. In freshly mined coal the amount of such sulfur is very small; weathering processes, however, may very materially increase the amount of sulfate present. Sulfur in the form of iron pyrites, or marcasite, may be quantitatively removed without oxidation of the organic sulfur as follows: A dilute solution of nitric: acid is prepared having 1 part of concentrated HNO3 to 3 parts of water or with an approximate specific gravity of 1.12. The coal sample, ground to 100 mesh, is digested with this solution at room temperature for 3 or 4 days, filtered and evaporated to dryness, taken up with water, and acidified with hydrochloric acid. It is now ready for precipitation with barium chloride in the usual manner. If sulfate is present in the original sample to an appreciable amount, it should be removed by the procedure outlined above. It is not necessary here to give the methods for determining the two

Jan 1, 1920

By C. M. Shigley

The record of the largest magnesium plant in the country utilizing sea water as a primary raw material stands as another victory in the struggle for large-scale production of pure chemical elements from the oceans. Bromine was the first element to be economically and commercially recovered when, in 1933, a six million pound per year unit was built on the Atlantic Coast near Wilmington, North Carolina, by the Ethyl-Dow Chemical Co.' The bromine was reacted with ethylene to produce ethylene dibromide, a necessary associate of tetraethyl lead in ethyl antiknock fluid. Within eight years that plant was doubled and redoubled, and another large unit was put into operation at Freeport, Texas, taking bromine from the Gulf of Mexico. In 1940, in fortunate anticipation of the impending demand for magnesium and the limitations of the production from natural brines, the Dow Chemical Co. turned again to the sea, and designed and erected a plant at Freeport to produce 18,000,000 lb. of magnesium per year from sea water.2 In March 1941, two months after the new plant had been put into successful operation, construction of an 18,000,000-lb. Government-financed addition was started. Late in 1941, as a part of the $400,000,000 defense program intended to produce 600,000,000 to 700,000,000 lb. of magnesium per year, Dow was asked to build and operate for the Government a 72,000- ooo-lb. plant near its original plant at Freeport. Within a few days after the Japanese made their attack at Pearl Harbor, preparation of a site was started at Velasco, Texas, for the construction of the Texas plant of the Dow Magnesium Corporation—the largest known magnesium plant utilizing sea water as its raw matcrial. Less than six months after the first piling was driven, urgently needed magnesium was in steady production. Five months later, the plant had exceeded its rated capacity. It remained above rated production until the general magnesium curtailment was applied to Government-owned plants in September 1944. Credit for the construction and operation record of the Dow magnesium plant must be divided among the efforts of a very determined group of men, an extremely favorable location, and a simple process. It is with the two latter aspects of the plant that this article will deal. The site for the new enterprise was chosen near Velasco, Texas, on property bordering the Brazos River at a point approximately 6 miles inland from the original magnesium plant and 7 miles inland from the Freeport Harbor on the Gulf of Mexico. This location was far enough away from the operating units to reduce both interference from construction and the vulnerability of closely bunched manufacturing operations to the then feared air attack. Yet the distance inland was not too great for the economical construction of a barge canal from the harbor to serve both the transportation of raw

Jan 1, 1949

By H. A. Wahl

This paper presents methods of designing hydraulic fracture treatments in formations saturated with slightly compressible liquids. Howard and Fast describe the fluid-loss control resulting from the viscosity and compressibility effects of the reservoir fluid in terms of a fracturing fluid coefficient. However, for horizontal fractures, this coefficient is applicable to infinitely thick reservoirs. These methods of evaluating fluid loss from horizontal fractures during treatment differ from previous methods in that: (I) formation thickness is incorporated in the velocity function describing the rate of fluid loss to the formation; and (2) for a given thickness the relative position of the fracture to the horizontal boundaries of the reservoir or any interrnediate permeability barrier is incorporated in the design procedure. This theory is applied to several actual and hypothetical field cases. The results of these calculations demonstrate that the eflect of formation thickness on fluid loss from horizontal fractures may result in fractures several times larger than predicted by other methods. INTRODUCTION Hydraulic fracturing has been the dominating well-stimulation technique during the last decade. From the time it was commercially available, fracturing has had a very favorable success ratio compared to other stimulation methods. However, numerous wells that were successfully stimulated remained economic failures. Only in the last few years has the oil industry recognized the importance of designing treatments for each well which will yield the maximum profit. This implies that for a given set of treatment conditions the size and general physical characteristics of the fracture can be determined. One of the outstanding contributions in the field of fracture design was presented by Howard and Fast.' In their paper, three flow mechanisms that control fluid loss from the fracture to the formation are defined: (1) viscosity effects of the fracturing fluid, (2) viscosity and compressibility effects of the reservoir fluid, and (3) wall-building effects of a treated fracturing fluid. The rate of fluid loss to the formation adjacent to a fracture is shown to be a function of time. For each flow mechanism the velocity function v(t) is expressed as a constant or fracturing fluid coefficient divided by the square root of time. This form of v(t) can be used in the Carter equation, as developed in the Howard and Fasc paper, to estimate the areal extent of fractures. This equation may be written as In the following sections the effect of formation thickness on fluid loss from horizontal fractures is evaluated when the controlling flow mechanism is the viscosity and compressibility of the reservoir fluids. The major assumptions inherent in the Carter equation are brought out in subsequent mathematical developments. THE EFFECT OF RESERVOIR FLUIDS ON FRACTURE EXTENSION When a fracture treatment is performed using a fracturing fluid identical to the reservoir fluid, the only flow mechanism controlling fluid loss is the viscosity and compressibility effects of the reservoir fluids. In developing a fracturing fluid coefficient for this mechanism, Howard and Fast considered a segment of the formation bounded by a unit area on the fracture face and extending to infinity in the direction of leak-off as shown in Fig. 1(a). The direction of leak-off z is normal to the fracture face. The equation governing the linear isothermal flow of fluid into this segment is where a = Eq. 2 is a form of the diffusivity equation. It is derived from the equation of continuity, Darcy's law and Eq. 3

E. S. BARDWELL,* Great Falls, Mont. (written discussion ?).-There are several points in. connection with the manufacture of ferromanganese in the electric furnace which it seems to me. might prove of interest in this connection. Recent observation of a, number of electric furnaces varying considerably in size and transformer capacity, and all working under the same conditions, shows the small furnaces to be much more efficient in operation than the large furnaces. The furnaces examined were all of the same type. The crucibles consisted of tanks varying in size from 71-z by 15 ft. by 4 ft. deep, to 12 by 20 ft. by 9 ft. deep, with linings formed of carbon electrode butts. The smaller furnaces had transformer capacity rated at 1500 k.v.a.; the largest furnace had a transformer rated at 3000 k.v.a. All of the furnaces were operated on three-phase, 60-cycle current, the three electrodes being in a straight line. The voltages varied from 65 volts in the smaller to 100 volts in the larger furnaces. The charges consisted of manganese ore, coal, iron turnings, and limestone in proper proportions. The small furnaces, operating at low voltage, were making good recoveries. The slag loss was low and the volatilization loss almost nil. The larger furnaces, operating at higher voltages, showed increased loss of manganese in the slag and greatly increased volatilization loss when working on the same charges as the smaller furnaces, or on charges similarly calculated. The exact reasons for this state of affairs are difficult to state; a number of factors probably contribute to the results obtained in the large furnaces. First as to the effect of the higher voltage on manganese content of the slags. Increasing the voltage of the furnaces apparently tends to promote irregular working. The current takes the path of least resistance; this means superheating in certain areas in the crucible and insufficiently high temperatures in adjoining areas. The partially reduced manganese in the cooler areas passes into the slag and escapes further reduction.

Jan 11, 1918

By Myron Rodgers

IN rock- or ore-crushing tests all data, in order to be valuable for study and comparison, should be obtained and tabulated under conditions as uniform as possible. The results of many such tests have no value for comparison, because of incomplete data and the lack of uniform conditions, screens and scale of sizing, etc. The purpose of this paper is to suggest a form of standard specifications which may be developed by the Milling Committee and approved by the A. I. M. E. for rock-crushing tests. It is not intended to discuss any theories of rock crushing. Reports of rock-crushing tests should include the following details: 1. Description of the machine employed (jaw or gyratory crushers, rolls, stamps, tube mills, Chilean mills, etc.). 2. Method and material (timber, concrete, etc.) of foundation. Much power is dissipated in the vibration of poor foundations. 3. Locality from which the rock or ore was obtained, and geological, mineralogical, and physical characters of the material. 4. The power consumption of the machine running with no load and with full load, the unit of power being 1 hp, per 24 hr. 5. The capacity of the machine in tons (of 2000 lb.) per 24 hr. 6. The duty in tons per horsepower-day. 7. The screen analysis of feed and product by the proposed A. I. M. E. standard screen scale. On the foregoing statement, the following remarks are offered.

Jan 9, 1915

By E. P. Jennings

Large deposits of titaniferous iron-ore occur at Caribou, an old silver-mining camp in Boulder county, Colo., 17 miles west by south of Boulder, and a few miles northwest of the tungsten-mines. Professor Regis Chauvenet1 published a part analysis of the ore many years ago, but gave no description of the wall-rock. Caribou hill, which contains both the silver-bearing veins and the iron-ore deposits, is a low dome of gabbro surrounded by the Archæan schists and gneisses of the Front range of the Rocky mountains, the peaks of which, a few miles west of Caribou, attain an elevation exceeding 12,000 ft. The gabbro stock is roughly elliptical in outline, with approximate diameters of 1 and 3 miles. The crest of the dome is 10,500 ft. above sea-level, and the town and ore-cleposits are 500 ft. lower. Outcrops of the iron-ore occur in the town and extend NW. for 2,000 ft., where they disappear under the swampy meadows of Caribou park. Portions of the deposit are covered by drift, but one continuous outcrop is 900 ft. long and from 200 to 250 ft. wide. A second deposit is 0.25 mile south of the town along the eastern slope of the hill. It is not as well defined as the north bed, but is approximately 1,000 ft. long and from 100 to 200 ft. wide. The easily disintegrated ore does not form prominent outcrops, but the outlines of the deposits are readily traced by the large amount of ore fragments that cover the ground. Trenches and pits sunk on the outcrop expose a roughly banded magnetic iron-ore, with pyroxene as the principal gangue-mineral. The Gabbro. This rock was classified in the field as a gabbro from the presence of pyroxene and striated feldspars, and for convenience the field-name will be retained.

Jan 1, 1913

By D. A. Dahlstrom

In the paper, a comparison was made between flowsheets using the screen bowl centrifuge and disc filters, respectively, as the primary dewatering device. The authors very effectively show that by raising feed temperature, mechanical dewatering is enhanced through reduced viscosity of the water. When a final coal moisture of 10% is required, the net effect of heating the feed is a reduction in thermal requirements because of the lower evaporated load on the dryer. The flowsheet comparison on this, however, was not completely correct. Disc filters do not generally utilize enhanced mechanical dewatering through increased temperature. Horizontal belt filters, through the optimal use of steam heating of the filter cake, have shown significant cost reductions over disc filters where steam is not used. In addition, the authors forgot to mention that there is a certain fraction of the feed that is so fine that it cannot be recovered by the centrifuge economically. That is the function of the filtration device shown in [Fig. 4]. In subbituminous pipeline coals, this fraction represents more than 10% of the feed. Even after flocculation and belt pressing, the moisture content in the fine fraction is 30%-40. Recent tests on a subbituminous pipeline coal slurry, compared an Eimco-Extractor horizontal belt filter with the screen bowl centrifuge flowsheet shown in [Fig. 4]. Mechanical dewatering was enhanced through the use of a steam dry zone after the initial dewatering zone. Vacuum pump horsepower was reduced by more than 50% through the use of condensers, and heat recovery was utilized to minimize thermal costs. Thermal drying to 10% moisture by weight was required in both flowsheets. The 0.5 wt% fines in the filtrate were flocculated and recycled to the filter, thus eliminating the belt press and solids mixers. When the three major operating costs (which normally account for 50%-75% of the coal operating costs) of steam, electricity, and flocculants at current prices were calculated, the flowsheets utilizing the Eimco-Extractor had cost savings vs the centrifuge flowsheet of 89c/t (81c per st) of surface dry coal. This advantage increases with increasing thermal and electricity prices. I congratulate the authors for the strides made with the screen bowl centrifuge. However, filtration flowsheets continue to be improved and their simplicity and low thermal and electrical requirements should not be so quickly dismissed.

Jan 1, 1984

By Arthur C. Simmons

The Pennsylvania-grade oil industry suffered a serious decline in 1938, which can be largely accounted for by the decrease in the use of lubricating oil. Production was considerably lower than in previous years and prices were very much lower. Operating profits undoubtedly were lower than the year 1933, for the average price of Bradford crude in 1938 was $1.898 as compared with $1.86 in 1933, and the difference in average price of $0.04 per barrel was more than offset by increased operating costs and taxes. Bradford Field Production in the Bradford field in the state of Pennsylvania averaged 36,759 bbl. per day in 1938 as compared with 41,300 bbl. in 1937. The decline in average daily production of 4541 bbl. can be attributed to low market price and pipe-line proration rather than to the actual physical capacity of the field. Pipe-line proration was in effect for the last eight months of the year and the daily average production per month fluctuated between a maximum of 41,852 bbl. per day in March 1938 and a minimum of 33,649 bbl. per day in November. Production figures for Bradford field have been corrected to include only the parts of the Bradford field that arc within the state of Pennsylvania, but the well-completion data for the Bradford field cannot be segregated and include those of the entire Bradford field, part of which is in Sew York state. Production from the Bradford field was obtained almost wholly by water-flooding and no radically new methods or practices occurred. Intensive research work was carried on both by individuals and companies and as a cpooperative enterprise, and minor improvements are gradually occurring in spacing, shooting, application of pressure and water conditions. Drilling Central and Southen Pennsylvania.—Pennsylvania production in central and southern Pennsylvania was obtained largely by air and gas repressuring together with the usual amount of natural production, and the repressuring operations in other than the Bradford field have not

Jan 1, 1939

By Arthur C. Simmons

The Pennsylvania-grade oil industry suffered a serious decline in 1938, which can be largely accounted for by the decrease in the use of lubricating oil. Production was considerably lower than in previous years and prices were very much lower. Operating profits undoubtedly were lower than the year 1933, for the average price of Bradford crude in 1938 was $1.898 as compared with $1.86 in 1933, and the difference in average price of $0.04 per barrel was more than offset by increased operating costs and taxes. Bradford Field Production in the Bradford field in the state of Pennsylvania averaged 36,759 bbl. per day in 1938 as compared with 41,300 bbl. in 1937. The decline in average daily production of 4541 bbl. can be attributed to low market price and pipe-line proration rather than to the actual physical capacity of the field. Pipe-line proration was in effect for the last eight months of the year and the daily average production per month fluctuated between a maximum of 41,852 bbl. per day in March 1938 and a minimum of 33,649 bbl. per day in November. Production figures for Bradford field have been corrected to include only the parts of the Bradford field that arc within the state of Pennsylvania, but the well-completion data for the Bradford field cannot be segregated and include those of the entire Bradford field, part of which is in Sew York state. Production from the Bradford field was obtained almost wholly by water-flooding and no radically new methods or practices occurred. Intensive research work was carried on both by individuals and companies and as a cpooperative enterprise, and minor improvements are gradually occurring in spacing, shooting, application of pressure and water conditions. Drilling Central and Southen Pennsylvania.—Pennsylvania production in central and southern Pennsylvania was obtained largely by air and gas repressuring together with the usual amount of natural production, and the repressuring operations in other than the Bradford field have not

Jan 1, 1939

By E. J. Rapperport, J. P. Pemsler

We have made calculations to evaluate the sensitivity of atomic absorption as a technique to measure vapor pressure changes with temperature. Our conclusion, supported by the experimental findings presented in this work, is that the ultimate sensitivity of the technique is well below lo-' Torr. This magnitude of vapor pressure sensitivity makes the method extremely attractive for thermodynamic studies. Atomic absorption techniques have been used previously in this connection by Scatchard and Boyd' and by vidale2 with a much lower sensitivity reported. Scatchard and Boyd's work measured cadmium pressure over Ag-Cd alloys in the range 0.02 to 0.3 Torr, and Vidale estimated that sensitivities of only 10"5 to 10"6 Torr are to be expected. Atomic absorption appears to be particularly well-suited to thermodynamic studies for several reasons: A) It is extremely sensitive; our experiments indicate an ability to measure vapor pressure changes of 10"9 Torr. B) It is highly selective; there is seldom interference among the resonant wavelengths of the various species. C) It may be performed in an absorption cell under static conditions. This alleviates such problems as surface impoverishment of alloys, attainment of equilibrium, and temperature measurement and control. D) Simultaneous, or near-simultaneous, vapor pressure measurements may be made for several elements in a given system. Experimental. The physical basis of the technique is the highly selective absorption of particular wavelengths by specific atomic species. In most atomic absorption work the element of interest is incorporated into a hollow cathode lamp to provide a characteristic spectral source of high intensity. The spectra lines characteristic of the element in the cathode are attenuated by atoms of that element in the radiation path. Radiation from silver or cadmium hollow cathode lamps was directed along a path containing a 10-cm evacuated silica cell. The cell was positioned within a silica windowed furnace and contained silver, cadmium, or an Ag-Cd alloy. As the furnace temperature was elevated, the number of atoms of the absorbing element in the vapor phase within the cell rose, and the resonant radiation was increasingly absorbed. Intensities were measured by passing the radiation through a Techtron Model AA-4 one-half meter grating atomic absorption spectrometer equipped with a photo-multiplier detector. In order to minimize instabilities in the source, the hollow cathodes were allowed to warm up for several hours and were run at only 2 5 to 30 pct of their maximum rated amperage. In addition the attenuated beam was monitored before and after each reading. The attenuation of resonant wavelengths may be related to vapor pressure by the following relationships.

Jan 1, 1969