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By Marie L. V. Gayler

Without diffusion taking place in liquid metals and alloys, no castings could be made; it is therefore the most important factor affecting the structure of metals. Diffusion involves the interchange of atoms, a process which takes place during the life history of an ingot. In the liquid, atoms are in a state of high thermal agitation, but this thermal vibration is reduced in amplitude with falling temperature. When solidification sets in, the atoms arrange themselves on an ordered space lattice and the changes in structure which take place in the solid are due to the interchange of atoms on this space lattice. The rate of atomic interchange—e.g., of diffusion—is most rapid at temperatures close to the melting point and decelerates as the temperature is lowered. At room temperature, the rate of diffusion is practically negligible in most alloys, and any change in structure can only be brought about by using methods which will accelerate the rate of diffusion. The rate of diffusion depends on three factors (I) temperature; (2) concentration gradient and (3) activation energy. The growth of grains and particles in the solid alloy also depend on these factors and are therefore intimately associated with diffusion. The rate of homogenization in a cast alloy depends on several factors, such as: (I) rate of solidification, which involves grain and particle size which, in their turn, depend on diffusion: (2) the nature of the constituents; (3) the temperature interval between the melting point of the metal or alloy and the temperature at which it is being heat-treated. It is well known that coarse, cast structures are extremely difficult—if possible— to homogenize, and the finer the grain size and particle size, the more readily solid solution will take place. The rate of diffusion depends, also, largely on the nature of the constituents; for instance, copper and magnesium form solid solutions with aluminum quite readily but nickel and iron do not; neither do certain intermetallic compounds, such as alpha and beta FeSi. Furthermore, the actual formation of intermetallic compounds may be a very slow process, particularly when they are formed in the solid state as equilibrium products. For example, BFeSi is formed in the solid as the result of the reaction aFeSi + A1 —+ PFeSi. The particles of aFeSi become surrounded with a reaction ring of PFeSi. This layer is formed as the result of diffusion of atoms taking place between the aluminum matrix and aFeSi. As the amount of aFeSi surrounding the core of aFeSi increases the concentration gradient becomes low and so the rate of diffusion of atoms also decreases until it practically ceases. This occurs after a comparatively thin layer of ßFeSi has been formed. It follows that when intermetallic compounds of this type are formed in the solid, as the result of diffusion, it is generally impossible ever to attain equilibrium, since the forma-

Jan 1, 1944

By W. A. Jr. Slippy, E. P. Dahlberg, R. B. Reed-Hill

A large room-temperature mechanical-hysteresis effect under cyclic tensile loading was observed in zivconium specimens prestrained at 77°K so as to form large numbers of (1121) twins. The observed hysteresis loss was a maximum when the prestrain was just under 1 pct It also depended strongly on the maximum applied cyclic stress, but only moderately on loading rate and temperature (-72°to 100°C). The phenotnena have also been studied in terms of the elastic aftereffect where the data has been found to cotlforln closely to the functional relationship between strain and time, c = -RT/a In tank ft. t to)/Zr, for strains cts large as about 10-4 This eyication can be derived directly from the strain-rate equation There may be important commercial implications to the present discovery since it appears that within rather wide limits it may be possible to obtain any desired magnitude of damping capacity in zirconium melal. The damping propevties may also be given directional characteristics. It is shown that the observed anelaslic phenomena can he explained on the assumiplion that they are the resuilt of stress-induced twin-boundary movements in which the average twin increases its thickness by only a few percent. In polycrystalline zirconium, a grain is least favorably oriented for slip when its basal plane, containing the (1130) slip directions, lies nearly perpendicular to the principle normal stress. Mechanical twinning is favored by this orientation and under simple tensile deformation at room temperature the primary twinning mode is {1012).' The (1012) twinning shear is small (0.17) so that, during deformation, twin growth does not greatly enhance ductility. At 77°K, on the other hand, the predominant twinning mode shifts to {1121), and many thin (1121) twins can form at small strains.' Twins thus nucleated can grow readily during subsequent room-temperature deformation and permit easy deformation in unfavorably oriented grains. In addition, the (1131) twinning shear is large: 0.63. These facts have lead to a process' for greatly improving the room-temperature ductility of zirconium when it contains a sizable fraction of grains with basal planes nearly normal to the stress axis. Optimum results are obtained by slightly less than 1 pct prestrain. The effect is large so that a 50 pct elongation increase is readily attained. A large room-temperature mechanical-hysteresis effect has also been observed in zirconium specimens prestrained at 77°K. The present paper is concerned with some aspects of this effect which the experimental observations strongly indicate is primarily the result of strain-induced {1121) twin-boundary movements. This clearly suggests that mechanical twins formed by plastic deformation can cause anelastic effects similar to those previously observed2 for annealing twins and twins associated with phase transformations. EXPERIMENTAL PROCEDURES All specimens were prepared from arc-melted sponge zirconium plate stock as previously described,3 which has a preferred orientation with basal planes aligned parallel to and uniformly distributed around the rolling direction. Both lonti-tudinal and transverse tensile specimens, with axes parallel and transverse, respectively, to the plate rolling direction, were cut from this plate. In a longitudinal specimen most grains are favorably oriented for slip, while in a transverse specimen a large fraction are unfavorably oriented. Prestraining at 77°K was performed in two ways. In one, annealed zirconium plate stock was cooled in liquid nitrogen and then rolled in the transverse plate direction to strains varying from 0.5 to 12 pct. Cylindrical 1/8-in.-diameter by 1-1/4-in.-gage-length tensile specimens were machined from this material. In the other, previously machined tensile specimens were prestrained in tension at 77°K between 0.2 and 3.8 pct. Type FA 25-12 SR4 strain gages were cemented to all specimen gage sections. All tests were performed on an Instron testing machine of 10,000-lb capacity. EXPERIMENTAL RESULTS Fig. 1 shows a typical two-cycle room-temperature stress-strain diagram for a specimen prestrained 0.65 pct by rolling at 77°K. The maximum stress in both cycles was 14,500 psi. Note that in the first cycle the loading and unloading curves are unsymmetrical so that a residual strain, er, remains after unloading. In the second cycle the stress-strain curves form a nearly symmetrical hystere-

Jan 1, 1965

By B. D. Lichter

The lattice parameters of zirconium and zirconium-oxygen solid solutions (hcp) were determined from measurements of back-reflection X-ray photograms obtained at 29°C using a symmetrical focussing camera. The following linear equations between parameters (c,a) in angstrom units (10-8 cm) and atom ratio (m) of oxygen to zirconium were obtained: c = 5.14764 + 0.2077m a =3.23168 + 0.1099m. The linear equations given are valid over the range 0 to 5 at. Pct 0. The accuracy of individual parameter measurements approaches the limiting accuracy determined by the spectral broadening of the incident characteristic radiation, and exceeds the accuracy of previously reported values. THE present work was undertaken in order to determine the lattice parameters of zirconium-oxygen solid solutions with an accuracy that allows quantitative determination of oxygen in zirconium. The results indicate that this is possible if very careful measurements are made, since the parameter change is only a few hundredths of a percent per at. pct 0.1, 2 In the present investigation the desired accuracy was achieved with large-grained samples using a back-reflection focussing camera and maintaining good temperature control during exposure. In addition a digital computer was used for calculation of the parameters by means of an analytical extrapolation.37 Suitable diffraction photograms were obtained from large-grained samples by using a modification of the technique described by Graf and Monteil.5 This consists of simultaneous rotation and oscillation of the specimen about two mutually perpendicular axes during exposure. Whereas, normally the upper limit of grain size is about 50 µ for useable diffraction photograms, this technique allows extending the upper limit of grain-size to exposure of a single crystal. EXPERIMENTAL Preparation of Alloys for X-ray Diffraction—Zir-conium, designated as hafnium-free, Westinghouse "Grade 1," was swaged from l/2-in.-diam crystal bar to 3/8-in.-diam rods. Substantially all of the hydrogen was removed from the zirconium by annealing at 1200°C in a high dynamic vacuum. The rods were then swaged to 0.2 in. diam without intermediate annealing, and 2 in. lengths were cut for alloying with oxygen. Samples for chemical analysis were taken from portions of the rods between each 2 in. length. Chemical analysis of the dehydroge-nated zirconium is given in Table I. Commercial tank oxygen (99.5 pct 0) was condensed in a liquid nitrogen-cooled trap, and part of the condensate was slowly reevaporated into 5-liter storage flasks. Nitrogen remained as a reactive impurity, and the calculated maximum increase in nitrogen content after a 5 at. pct 0 addition to zirconium was 50 ppm by weight. However, chemical analyses of several of the prepared alloys indicated that the maximum increase in nitrogen content was 10 ppm. The storage flasks, a Sieverts-type gas burette and manometer, and associated traps, pumps, and pressure gauges were connected through a glass high-vacuum manifold to comprise the gas addition system. A fused silica tube, connected to the mani-

Jan 1, 1961

By Cyril Wells, Robert F. Mehl

THE two earlier papers in this series1,2 presented data on the rate of diffusion of carbon and of manganese in gamma iron. Apart from their scientific interest, these [] data are needed chiefly in order to treat data on carburization, on the rate of formation of pearlite, and on the rate of austenizing in a quantitative way. 1,2,9,10 In the present investigation rates of diffusion of nickel in -?-Fe over wide temperature and concentration ranges have been determined, and the effects of carbon, of impurities, and of grain size on these rates have been studied. Claussen,3 using the data of Fry,4 has calculated the diffusion coefficient of nickel [ ] in -?-Fe as 9.2 X 10-11 sq. cm. per sec. at 1200T., but had no data from which to calculate the variation of D with concentration, temperature, and percentage of carbon. METHOD AND MATERIALS Method.-Nickel was diffused along the axis of a cylindrical specimen across a concentration gradient, concentration-penetration curves were determined and D values calculated from Grube or Matano solutions.5 Details of the method are given

Jan 1, 1941

By Elton A., Youngberg

The Holden mine operated by the Chelan Division of the Howe Sound Co. is on the east slope of the Cascade Range in north central Washington on the south slope of Railroad Creek valley at an elevation of 3500 ft. The mine may be reached by a 40 mile boat trip from the town of Chelan which is at the southern tip of Lake Chelan, to Lucerne at the mouth of Railroad Creek and an 11 mile bus ride up Railroad Creek to Holden. All freight and concentrate is moved over this route to Chelan Falls on the Columbia River which is on the railroad four miles below the town of Chelan. The mine is now producing 2000 tons of gold, copper, and zinc ore per day which is treated in the Holden mill. Gold-copper and zinc concentrates are made, the first of which is shipped to Tacoma, Wash., and the latter to Kellogg, Idaho, for smelting.

Jan 1, 1949

By F. C. Canney

Geochemical prospecting seeks hidden mineral deposits by sampling for variations in the chemical composition of naturally occurring materials. Usually the samples are of soils and other products of weathering and erosion-surface materials extremely susceptible to contamination by human activities. Except when a survey is conducted well away from populated areas, contamination is an ever-present hazard. The program's success is particularly endangered when the contaminants are the elements sought; if these occur erratically throughout an area, spurious anomalies completely unrelated to mineralized areas can be formed. Evenly distributed contamination can be dangerous too, if it raises the background to such a level that true anomalies can no longer be easily detected. Suppose, for ex- ample, that in an area where the lead background is 20 parts per million the soil over a lead vein contains 1000 ppm of lead. Here the contrast would be 50 to 1, which is very satisfactory for geochemical surveying. Now if 1000 ppm of lead from some source were added evenly to the soil in this area, the contrast would be reduced to about 2 to 1, and the anomaly would no longer be readily detectable because a threshold of significance twice the value of the background is the minimum generally used for interpreting geochemical data.

Jan 2, 1959

By Fred C. Bond

There is acute need for a method that will measure the size distribution of finely divided materials, particularly when the particle sizes are smaller than the openings of the finest screen cloth regularly available for testing. Several methods and types of apparatus are in common use, but none are entirely satisfactory for all purposes. The commonest methods are microscopic grain counts, elutriation by liquids or air, and sedimentation. Valuable results have been secured by air elutriating devices, typified by the Haultain Infra-Sizer and the Pearson Air Analyzer. These are especially useful in obtaining sized fractions that can be examined and analyzed separately. They are particularly advantageous because the sizes of the samples produced are adequate for a considerable amount of subsequent manipulation and testing. The sedimentation methods, such as the Wagner and Klein turbidimeters, and the sedimentation balance, do not deliver sized fractions, but they do provide a means for reasonably rapid comparative determina-tions of fineness and surface area, which are important in many industries. The sedimentation balance consists essentially of a balance pan suspended in a liquid that contains falling particles. These are weighed as they settle onto the pan, and the time rate of settling is determined. The size distribution is computed from the settling rate. The balance appears to be inherently more accurate than any of the other methods, and it has served a useful purpose in the study of numerous problems, but there have been limitations which have restricted its scope of application. Because of the essential simplicity of the method, it was felt that intensive investigation might lead to modifications that would make it a valuable tool [or the operators in industries that require precise information regarding the results secured from grinding equipment. A large number of size-distribution determinations below 200 mesh were required in connection with a particular research problem in fine grinding. The sedimentation balance was used in this investigation, and a technique was gradually developed that ultimately gave good results. A serious difficulty appeared early in the work. It was discovered that less material always settled on the sedimentation pan and more on the bottom of the containing jar than could be accounted for by calculation, and also that the material that settled to the bottom of the jar outside the edges of the pan was considerably finer than that on the pan. This segregation was so great that the distribution obtained for the finer sizes was obviously very much in error; material ground to about the degree of comminution of cement might have only 60 per cent of the calculated weight actually settling on the pan, and the error increased with the fine-

Jan 1, 1943

By Fred C. Bond

THEM is acute need for a method that will measure the size distribution of finely divided materials, particularly when the particle sizes are smaller than the openings of the finest screen cloth regularly available for testing. Several methods and types of apparatus are in common use, but none are entirely satisfactory for all purposes. The commonest methods are microscopic grain counts, elutriation by liquids or air, and sedimentation. Valuable results have been secured by air elutriating devices, typified by the Haultain Infra-Sizer and the Pearson Air Analyzer. These are especially useful in obtaining sized fractions that can be examined and analyzed separately. They are particularly advantageous because the sizes of the samples produced are adequate for a considerable amount of subsequent manipulation and testing. The sedimentation methods, such as the Wagner and Klein turbidimeters, and the sedimentation balance, do not deliver sized fractions, but they do provide a means for reasonably rapid comparative determinations of fineness and surface area, which are important in many industries. The sedimentation balance consists essentially of a balance pan suspended in a liquid that contains falling particles. These are weighed as they settle onto the pan, and the time rate of settling is determined. The size distribution is computed from the settling rate. The balance appears to be inherently more accurate than any of the other methods, and it has served a useful purpose in the study of numerous problems, but there have been limitations which have restricted its scope of application. Because of the essential simplicity of the method, it was felt that intensive investigation might lead to modifications that would make it a valuable tool for the operators in industries that require precise information regarding the results secured from grinding equipment. A large number of size-distribution determinations below 200 mesh were required in connection with a particular research problem in fine grinding. The sedimentation balance was used in this investigation, and a technique was gradually developed that ultimately gave good results. A serious difficulty appeared early in the work. It was discovered that less material always settled on the sedimentation pan and more on the bottom of the containing jar than could be accounted for by calculation, and also that the material that settled to the bottom of the jar outside the edges of the pan was considerably finer than that on the pan. This segregation was so great that the distribution obtained for the finer sizes was obviously very much in error; material ground to about the degree of comminution of cement might have only 60 per cent of the calculated weight actually settling on the pan, and the error increased with the fine-

Jan 1, 1939

By Fred C. Bond

There is acute need for a method that will measure the size distribution of finely divided materials, particularly when the particle sizes are smaller than the openings of the finest screen cloth regularly available for testing. Several methods and types of apparatus are in common use, but none are entirely satisfactory for all purposes. The commonest methods are microscopic grain counts, elutriation by liquids or air, and sedimentation. Valuable results have been secured by air elutriating devices, typified by the Haultain Infra-Sizer and the Pearson Air Analyzer. These are especially useful in obtaining sized fractions that can be examined and analyzed separately. They are particularly advantageous because the sizes of the samples produced are adequate for a considerable amount of subsequent manipulation and testing. The sedimentation methods, such as the Wagner and Klein turbidimeters, and the sedimentation balance, do not deliver sized fractions, but they do provide a means for reasonably rapid comparative determina-tions of fineness and surface area, which are important in many industries. The sedimentation balance consists essentially of a balance pan suspended in a liquid that contains falling particles. These are weighed as they settle onto the pan, and the time rate of settling is determined. The size distribution is computed from the settling rate. The balance appears to be inherently more accurate than any of the other methods, and it has served a useful purpose in the study of numerous problems, but there have been limitations which have restricted its scope of application. Because of the essential simplicity of the method, it was felt that intensive investigation might lead to modifications that would make it a valuable tool [or the operators in industries that require precise information regarding the results secured from grinding equipment. A large number of size-distribution determinations below 200 mesh were required in connection with a particular research problem in fine grinding. The sedimentation balance was used in this investigation, and a technique was gradually developed that ultimately gave good results. A serious difficulty appeared early in the work. It was discovered that less material always settled on the sedimentation pan and more on the bottom of the containing jar than could be accounted for by calculation, and also that the material that settled to the bottom of the jar outside the edges of the pan was considerably finer than that on the pan. This segregation was so great that the distribution obtained for the finer sizes was obviously very much in error; material ground to about the degree of comminution of cement might have only 60 per cent of the calculated weight actually settling on the pan, and the error increased with the fine-

Jan 1, 1943

By Fred Bond

THERE is acute need for a method that will measure the size distribution of finely di-vided materials, particularly when the par-ticle sizes are smaller than the openings of the finest screen cloth regularly available for testing. Several methods and types of apparatus are in common use, but none are entirely satisfactory for all purposes. The commonest methods are microscopic grain counts, elutriation by liquids or air, and sedimentation. Valuable results have been secured by air elutriating devices, typified by the Haultain Infra-Sizer and the Pearson Air Analyzer. These are especially useful in obtaining sized fractions that can be examined and analyzed separately. They are particularly advantageous because the sizes of the sam-ples produced are adequate for a consider-able amount of subsequent manipulation and testing. The sedimentation methods, such as the Wagner and Klein turbidimeters, and the sedimentation balance, do not deliver sized fractions, but they do provide a means for reasonably rapid comparative determina-tions of fineness and surface area, which are important in many industries. The sedimentation balance consists essen-tially of a balance pan suspended in a liquid that contains falling particles. These are weighed as they settle onto the pan, and the time rate of settling is determined. The size distribution is computed from the set-tling rate. The balance appears to be in-herently more accurate than any of the other methods, and it has served a useful purpose in the study of numerous problems, but there have been limitations which have re-stricted its scope of application. Because of the essential simplicity of the method, it was felt that intensive investiga-tion might lead to modifications that would make it a valuable tool for the operators in industries that require precise information regarding the results secured from grinding equipment. A large number of size-distribu-tion determinations below 200 mesh were required in connection with a particular research problem in fine grinding. The sedimentation balance was used, in this investigation, and a technique was gradually developed that ultimately gave good results. A serious difficulty appeared, early in the work. It was discovered that less material always settled on the sedimentation pan and more on the bottom of the containing jar than could he accounted for by calculation, and also that the material that settled to the bottom of the jar outside the edges of the pan was considerably finer than that on the pan. This segregation was so great that the dis-tribution obtained for the finer sizes was obviously very much in error; material ground to about the degree of comminution of cement might have only 60 per cent of the calculated weight actually settling on the pan, and the error increased with the fine-

Jan 1, 1939

By Alexandre Mitinsky

The theory of elasticity, the science of the strength of materials, and all our calculations regarding engineering structures are based on Hooke's law, that in loaded bodies the deformations are proportional to the load producing them. Without this law it would be impossible to design intelligently engineering structures such as bridges, frames, axles, etc. This being the case, the proportional limit,l that is, the point at which deformation ceases to be proportional to load, is the most important factor in engineering design. Further, the working fiber stress should be fixed in reference to the proportional limit instead of, as is usual, in reference to the ultimate strength. The incorrect use of the ultimate strength instead of the proportional limit in setting the working fiber stress is probably due to two reasons: (1) it is a more delicate operation to measure the proportional limit; (2) it is usually assumed, though incorrectly, that the proportional limit is determined by the ultimate strength. In Germany the poin't at which permanent set first appears is often taken instead of the proportional limit. The two points will coincide if Gerstner's law, that elastic deformations are proportional to the loads producing them both before and after permanent set, is true; and the limit of proportionality and the elastic limit or point of permanent set will both be represented on a stress-strain diagram, by the point at which the line ceases to be a straight line and becomes curved or changes its inclination. It is to be further noted that the difference in definition between proportional limit and elastic limit introduces a difference in methods of determination in the testing laboratory. The German method of determining the elastic limit by alternately loading and unloading the test specimen is a lengthy process and time has in itself a very considerable influence on the results of physical tests.

Jan 1, 1916

By W. W. Dudley

Inflow of ground water is an important engineering and safety consideration during construction of large openings underground. The initial step in predicting groundwater inflow involves hydraulic tests in exploratory drill holes. Zones within the area of interest are isolated in the drill hole by inflatable packers and are tested by measuring the water level responses to applied hydraulic stresses. These responses may then be translated into significant hydraulic characteristics of the tested rocks such as transmissivity, hydraulic conductivity, hydraulic potential, and storage coefficient by using a type-curve solution. Once the geometry and necessary hydraulic characteristics have been determined for the rock in the vicinity of the proposed opening, a model can be developed using certain assumptions that will lend itself to treatment with available mathematical methods. The mathematical method applied to the model considers conditions of partial penetration and nonsteady-state, leakyartesian, constant-drawdown discharge of ground water. A type-curve solution results in a curve that gives the variation of discharge (inflow) with time. This technique of predicting ground-water inflow has been used in planning construction of cylindrical chambers for use in underground nuclear experiments by the U.S. Atomic Energy Commission. These chambers have been constructed in low-permeability rocks at depths as much as 6000 ft and under hydraulic heads of thousands of feet.

Jan 1, 1973

By R. L. Whiting, H. J. Ramey

The basic study from which this paper was prepared was started as the result of the growing need throughout the world for increasing quantities of energy in all forms. Quite obviously, natural forms of energy that are readily available at low development cost are those in greatest demand. The underdeveloped countries — and particularly those having little or no petroleum resources — are the countries in which the most interest is being shown in the newer energy sources. One of the least expensive energy sources is natural geothermal steam.'-* Although this form of energy has been recognized for centuries, it has been only during the past 20 years that serious efforts have been made to harness it. Natural geothermal steam energy in Italy, New Zealand, Mexico, Japan, and California is now being produced through wells to drive turbines and generate electricity. Further, active exploration for natural geothermal steam is being conducted in Hawaii, Fiji, Taiwan, Chile, Russia, Greece, and Katanga. It is surprising to find that most geothermal steam exploration is in the "steam seep" stage. That is, surface studies are made and exploratory wells are drilled in the general area of steam seeps. However, in the larger geothermal steam areas, there have been efforts to apply the most modern geological and reservoir engineering principles in order to define the reservoir parameters, particularly those relating to estimates of reserves and future productivity. This paper is concerned with the development of appropriate equations and techniques to facilitate these estimates. Production of natural steam or hot water presents problems different from those experienced in the production of oil and gas. For example, steam or hot water systems may be essentially single-component systems, while hydrocarbon systems are most frequently multicomponent fluid systems. Heat effects are much larger for water than for hydrocarbon systems; and the natural steam production may or may not be isothermal, while production of petroleum reservoirs is considered normally to be isothermal. Petroleum reservoir engineering principles may be applied to natural steam or hot water reservoirs if the inherent differences in the systems are considered. The basic considerations involved in geothermal steam reservoir engineering are: thermodynamics, physical and thermal properties of water, materials and energy balances, fluid influx, and performance matching and predicting. Thermodynamics Fig. 1 is a pressure-temperature diagram for the liquid-vapor region for pure water, showing the critical point and five other points representing possible initial conditions for a geothermal steam reservoir. To generate a physical appreciation for the mechanics of natural steam production, it is helpful to consider

Jan 1, 1970

By C. C. Herrick

The vapor pressure of indium has been measured by the torque-effusion technique, as a function of temperature between 1102o and 1422oK. For liquid indium, the vapor pressure (in atmospheres) can be represented by the equation -R In P = 5.782 x104/T - 25.29from 1000o to 1422oK. Extrapolation yields a calculated normal boiling point of 2329°K and a heat of vaporization at 298 oK of 58.09 kcal per mole by the third-law method and of 58.39 kcal per mole by the second-law method. Calculations indicate that the free-energy functions of Hultgren are to be preferred to those of Guruich. BECAUSE of the potential uses of liquid metals, it is important that convenient experimental methods be developed which will lead to a sufficient body of thermodynamic data so that reasonable estimates of properties of liquid metals can be made. Indium is particularly well-suited to investigation, since it remains liquid over a long temperature interval, it alloys readily, suitable containers for it are easily procured, and relatively few investigations of its thermodynamic properties in the region above 1000°K have been made. PREVIOUS RESEARCH The first determination of the vapor pressure of indium was made by Anderson,' using the Knudsen method and silica-lines stainless-steel cells. Kohlmeyer and spandau2 determined the normal boiling point, and a mass-spectroscopic investigation has been made by Lyubimov and Lyubitov.3 (Unfortunately, only an equation representing the data of the latter investigators has been available to us.) Hultgren et al.4 and Gurvich5 have published discordant tables of the free-energy functions for indium. EXPERIMENTAL METHOD The torsion-effusion principle has been described amply in the literature.8,7 With this method, one observes the angular deflection induced by effusion of vapor from a multihole effusion cell which is suspended from a filament producing a small rotational restoring force. The pressure within the effusion cell can be computed from the relation ziaifiai where k is the torsion constant of the filament, 6 is the observed angular deflection, and ai, fi, and qi are the area, force factor, and moment arm of the ith effusion orifice. The force factor f is analogous to the Clausing factor,' and corrects for the reduction in effusive force attributable to the finite geometry of the effusion orifice. Schultz and Searcy' have tabulated the force factors for various tube geometries. EXPERIMENTAL APPARATUS The physical arrangement employed in this study is shown in Fig. 1. The furnace elements are six Globar heat rods with 15-in. hot zones. Temperature is maintained to * 1°K by a Beck mechanism driving two 26-amp Powerstats in parallel. A Pt (Pt, Rh 10 pct) thermocouple serves as the sensing element. Four inner tubes act as vibration isolators; the air pressure required for maximum isolation was determined empirically, and is maintained by a solenoid valve. The tungsten fiber, 9 by 0.002 in., is joined to an 0.008-in. tungsten wire or graphite rod via a machined lightweight chuck.

Jan 1, 1964

By J. HUNER

Twenty-four new fields were found in Louisiana during 1945. Of this number 15 were oil fields, eight were gas condensate, and one a dry gas field. None of these fields, with the exception of West Delhi, is as yet of any great consequence. The Weeks Island field in Iberia Parish may eventually develop into a considerable reserve.

Jan 1, 1946

By E. A. Gulbransen, W. S. Wysong

THE behavior of molybdenum and its surface oxides in oxidizing and reducing gas atmospheres and in high vacua at elevated temperatures is a question of scientific and technical importance The use of molybdenum as a metal or as an important component in alloys in oxidizing atmospheres at elevated temperatures has been limited because of the unprotective nature of its oxide film and the volatility of this oxide at moderate temperatures. This communication will present results of a vacuum microbalance study 1,2 of the following problems. (11) the oxidation kinetics in the temperature range of 250° to 450°C; (2) the reduction with pure hydrogen of thin oxide films formed on molybdenum; (3) the volatility of the thin oxide films, and (4) the vacuum oxidation of molybdenum at high temperatures. Molybdenum is an interesting metal to study for the following reasons: (I) although the oxide-to-metal-volume ratio is greater than one, the metal is not considered protective; (2) the metal oxidizes readily at temperatures of 250°C and higher; (3) the oxides of the metal are reduced at temperatures as low as 500°C by pure hydrogen; (4) the oxide MoO3 melts at 795°C; and (5) the oxides of molybdenum are volatile at moderate temperatures. The following variables are studied in the oxidation kinetics. time, temperature, pressure, surface preparation, surface area, concentration of inert gas in the lattice, cycling procedures in temperature, vacuum effect and high temperature vacuum oxidation The general interpretation of many of these factors has been previously discussed. LITERATURE The oxidation of molybdenum has not been studied critically. Although" many studies have probably been made on the kinetics of the oxidation process, none has been reported in the literature available to us. The crystal structures found in the oxidation of molybdenum have been studied by Hickman and Culbransen 4 Their results showed that MoO2 is the oxide which is stable in contact with the metallic subgtrate throughout the temperature range 300 to 700°C. As the film thickens in the low temperature range, MoO3 becomes predominant on the surface. Above 400°C, Mo03 is no longer observed, Mo02 being the only oxide found. Hagg and Magneli5 have shown from an X ray study that the a-phase, orthorhombic MoO3 is stable up to 1050°C. Two other phases, ß and ß', with compositions close to Mo02 90 are also obtained The formula for the ß phase is not given but that of the ß' phase is defined as Mo9026. The ß' phase is found to be built upon a monoclinic unit cell. A -?-phase is isolated from a preparation M00275 heated for 17 hrs at 670°C. This phase is

Jan 1, 1947

By James L. Sweeney

The Project Independence Evaluation System (PIES) is a complex evaluation, forecasting, and analysis system which represents the U.S. energy production, conversion, transportation and consumption activities. The system includes various models: An econometrically estimated energy demand model, used to evaluate the final demand functions for energy commodities ; A collection of supply models, used to evaluate the cost curves or supply curves for domestic crude oil, natural gas, coal ; An integrating model used to describe energy conversion and transportation activities and to calculate prices which equate energy supply and demand in each market. PIES has been used to generate conditional forecasts of the 1980, 1985, and 1990 states of the energy system--forecasts conditional upon the world oil prices, the energy policy environment, and other uncertainties. Scenarios have been structured to separately examine conservation initiatives, domestic energy supply enhancements, an extensive electrification strategy, and oil and natural gas well -head price regulation. This paper presents the basic model, discusses its use for examining policy options, and describes several forecast results. The paper draws heavily upon work completed for the 1976 National Energy Outlook, published by the Federal Energy Administration.

Jan 1, 1977

By Richard W. Markley

The predominant methods for mining coal in the USA are room and pillar and longwall. Approximately 95 percent of the coal is mined by room and pillar and 5 percent by longwall. The U.S. Department of Energy (DOE) has an ongoing program to improve the rate, quality, and cost effectiveness of stabilizing the roof for both of these mining systems. In room and pillar mining, the installation of permanent roof support is often the task which paces the system operation, and it thus controls the level of production achieved during any mining shift. Two automatic roof bolt insertion equipment developments are discussed, as well as a flexible drill for operation in thinner seams. Progress will be reported on under- ground trials of a particular flexible drill which has been combined with a bolt inserter to form a compact, reliable module for retrofitting to continuous mining machines. In longwall mining, the use of hydraulic supports on the working face provides roof stability. The DOE has several trials ongoing with shield- type supports in difficult strata conditions which are described, as well as a co-funded project with the Bureau of Mines on a resin injection remedial method for consolidating a shear zone at one site. A project to improve the match of strata conditions to shield design is also described, which involves the use of a 1360 tonne vertical load mine roof simulator.

Jan 1, 1983

By Georges Fleming

The new burden preparation plant of ARBED Luxembourg, Belval- Works, which comprises 2 large sinter strands, is equipped with a process computer connected to a comprehensive process control system. The main jobs done by the computer are the control of the raw mix composition, and thus the monitoring of the stacking of the piles at the bed-blending plant, and the optimization of the sintering process. Among the optimization criteria, quality is considered as the most important. The sinter quality, characterized by the mechanical strength and the state of oxidation, is controlled automatically. The control system which we have dev loped is highly reliable; as a result, the standard deviation of Fe++, for the control of bivalent iron, has been narrowed to 0,5 % and the standard deviation of the IS0 + 6, 3 mm index, for the control of the mechanical strength, has been kept within 1 %. Thanks to these results, the combined savings in fuel consumption at the sinter plant and at the blast furnaces have covered the total costs of the optimization project in 2 years. By applying automatic control, the optimum driving range of the sinter plant has been defined and these new guidelines are used for monitoring the sinter production.

Jan 1, 1977

By J. J. Bowman, E. H. Dix

A lack of experimental data illustrating the effect of composition, particularly in respect to impurities, on the mechanical properties and corrosion resistance of aluminum-alloy die castings induced the authors and their associates to undertake a limited study of these relations. A number of commercial alloys and several experimental variations of a commercial alloy were used for the investigation. Mechanical property, growth, steam, paraffin, salt spray and atmospheric exposure tests were employed. This paper deals with the more accelerated tests and the results they have produced. It is concluded that a high-silicon alloy with all impurities except iron strictly limited to small amounts will develop an excellent resistance to corrosion and retain satisfactory mechanical properties and casting characteristics. As a direct result of this investigation an alloy of this character with superior corrosion resistance is now available commercially. In general, copper increases the strength and decreases the elongation and corrosion resistance. Tin reduces the mechanical properties and the resistance to corrosion. Iron reduces the elongation and, if excessively high, may adversely affect the tensile strength. Even excessively high iron contents do not affect the corrosion resistance, which is fortunate for the die caster as it is this element that is the most difficult to control. Nickel and zinc in limited amounts do not seem to affect the properties or corrosion resistance of at least the high-silicon alloy. Growth tests have confirmed the previous common belief that dimensional changes under either dry or wet conditions at 100" C. are too small to be of practical importance. Introduction The technical literature contains numerous papers describing die castings, their production, compositions and uses, but nearly all of these

Jan 1, 1935