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Teamwork: The famous first sentence of an essay en- titled Aphorisms, by Hippocrates, is as follows: "Life is short, the Art long, opportunity fleeting, experience treacherous, judgment difficult." The future of science does not depend so much on the number of scientists or the number of colleges, but rather on the individual qualities and the degree of perfection of a limited group of leading scientists and colleges. These are individual factors which require inherent talent which in turn is a condition evolved after generations of culture. Thus, very elaborate higher education for indiscriminate masses of humanity or students may not necessarily show the expected results. In other words, it is possible that higher specialized education should be given only to the few talented individuals, and their capacity and worth should be judged by as highly qualified and talented teachers. Quality is the greatest of all competitive aids. An essential qualification that must be possessed by a quality mineral industries college is a high caliber teaching staff, for the mineral sciences will advance in the coming years only if the leading minds of today are made avail- able as the mental springboards for our scientists of tomorrow. Mineral industries schools are finding it increasingly difficult to maintain a high caliber staff of instructors and administrators in competition with private business and governmental demands for similar

Jan 1, 1950

By Dermot M. Ross-Brown

Introduction Slope angles are one of the major factors affecting the shape of the final pit and the location of the walls Due to differences in geology, the optimum slope angles vary from pit to pit and within different parts of the same pit. Indeed, it is not unusual to have different slope angles for the top and bottom portions of the same cross section. The optimization of these slope angles is a major study in itself and this chapter is intended as a general introduction to the subject. It is not intended to be a comprehensive text for the absolute beginner The objective is to put the various aspects of slope stability analysis into relative perspective by describing the vari¬ous analytical techniques available and indicating when each may be most appropriately used References are made to the many excellent texts and papers on slope stability for the reader who does not have a formal training in soil or rock mechanics. In writing this chapter, an assumption has been made that a tentative mining plan has been drawn up, includ¬ing a preliminary estimate of the slope angles. It has also been assumed that all the necessary field and laboratory data has been collected and reduced to a form suitable for input into the stability analyses.

Jan 1, 1979

By W. A. McCurdy, Joseph W. Leonard, William F. Lawrence

INTRODUCTION Utilization from the Point of View of the Preparation Engineer The primary interest of the coal preparation engineer is in process design, operation, and maintenance to produce an acceptable product that can be sold at the greatest possible profit. Because of emphasis upon these interests, attention to other potential values of coal is sometimes neglected. The intent of this chapter is to alert the preparation engineer to the utilization possibilities of the product as well as the tributary coal flow moving through a modern coal preparation plant. The basis for any unrealized potential derives directly from the coal seam itself. Most coal seams consist of coal bands and benches sandwiched together in layers that differ visually from each other in physical structure and luster. Randomly selected physical and chemical ranges determined from layers of coal in a single seam can easily differ by as much as 30 Hardgrove grindability indices, 0.30 of a specific gravity point, 20 percentage points of ash, 6 percentage points of dry volatile matter, and 10 percentage points of total su1fur.l Similar wide variations exist for calorific value, seam moisture content, and, undoubtedly, for any other conceivable coal test parameter that might be used for comparative purposes. These observations all point to the long-established fact that coal is not homogeneous, as conventional analytical methods might tend to indicate, but is instead a highly heterogeneous substance.

Jan 1, 1979

By W. M. Gray

The determination of the state of stress existing at a point in any solid body requires the determination of the six components of the stress tensor relative to a convenient set of axes. One general method of doing this in rock is to make strain or deformation measurements associated with local relief of stress in a number of boreholes penetrating a limited volume in the vicinity of the point at which the stress is to be determined. The stress is assumed to be constant throughout this volume. Leeman1 has described a number of the instruments that have been developed for making deformation or strain measurements in boreholes. Panek2 has described the application of statistical methods to the determination of the average components of ground stress from sets of measurements made in boreholes by means of deformation meters of the type developed by the U.S. Bureau of Mines. In this paper attention is given initially to the strain cell developed for use on the flattened ends of boreholes by the Council for Scientific and Industrial Research (CSIR) , South Africa. The equations required for evaluating the average components of ground stress from measurements made by means of the CSIR strain cell are derived. These equations are similar in form to those applying to measurements made by the borehole deformation meter developed by the U.S. Bureau of Mines. The results of an investigation of the properties of the equations are described. These results are important in the practical use of both the instruments mentioned above and any instrument based on similar principles.

Jan 1, 1968

By Herbert R. Hanley

THE One Hundred and Twenty-sixth meeting-of the Institute, held in San Francisco, Sept. 25 to 29, 1922, was a success in every way. Character-istically, San Francisco presented climate suited, to the occasion, while the Committees on Arrangements left nothing undone that would contribute to the interest and entertainment of the members and their wives. There was a registration of over 230, and all sections, save three, were represented. In the technical meetings, under the leadership of Albert Burch in the mining session and C. W. Merrill in the milling session, the greatest interest was manifested in ore-hunting geology and modern ore-dressing methods. The general geologic phase developed numerous discussions and had for its aim the study and correlation of known data and the application-of these to the finding of commercial orebodies. The geologic features of the Comstock and their significance to the development of the present orebodies were discussed. This brought out matters of much technical interest as well as those of romantic nature in the history of the early life of that camp. The profitable application of modern milling methods to ores, non-commercial a short time ago, was discussed with much interest. The recent work on the Comstock ores occupied a conspicuous part in these discussions. Basic principles delineated by mathematical study of mechanical devices for the milling of ore came in for a prominent part in the program as well as the physical-chemical side of the processes devised for the winning of precious metals as a profit.

Jan 11, 1922

By Albert F. J. Bordeaux

The immediate vicinity of the sea-shore, affording special facility for the exportation of ores, makes it possible to work certain mines in the Vladivostok district, which, in more remote places of Siberia., would remain unproductive. Outside of the city of Vladivostok the population is small and the country is very little prospected. Additional discoveries of valuable deposits like the large body of calamine which has recently been opened in the neighborhood of earlier worked lead-silver ores, in the Tetiuhe valley, are still in the field of possibilities. For many years gold alone was produced, in part from the coastal rivers and in part from a quartz-vein on Askold island near Vladivostok. But the production is diminishing, and prospectors are looking for other rivers in the interior, such as the tributaries of the Ussuri. These rivers are now more accessible than formerly, due to the slow but gradual development of colonization by the Russian peasants. The few natives of the country, called Orodjones, are of the Chinese race. They resemble the North American Indian and are hardy fur-hunters. They have given some attention to placers and have already shown good specimens of gold-dust from the rivers Iman, Bikin, Noto, etc. Coal-mining was begun in the Vladivostok region more than 20 years ago, but in a somewhat irregular way. The industry is not as yet important and the best coal-seams are badly prospected, or are even neglected. Copper, lead, and iron exist in several places. The amounts give some encouragement to the anticipation that the discoveries will give rise to important metallurgical works. I here present a review of the various deposits, based upon such safe information as is in hand, when I have not drawn upon my personal observations. Fig. 1 is a map of Eastern Siberia, showing the mineral deposits.

Jan 1, 1913

By Karl S. Kurtenacker

In attempting to find a rapid and economical means for solving many of the subsurface problems that confront the highway engineer, the author for the past two years has utilized a Megger Ground Tester on resistivity surveys in conjunction with highway construction. Electrical surveys in connection with highway work are largely shallow depth surveys, thus differing from most other types of resistivity work. Consequently, the readings are affected by a great many qualifying factors such as the density and moisture content of the media under observation and the amount of weathering and leaching. In most cases the surface layer is decidedly heterogeneous in character, and, because of the great number of side hill cuts, the second layer, which in most cases is rock overlain by some sort of surface soil, silt, or debris, seldom lies in a horizontal position. Shallow strata, lacking homogeneity and not lying in a horizontal position, do not lend themselves readily to accurate theoretical interpretations, therefore the author has used empirical rules to a large extent in interpreting depth soundings. The following empirical rules of interpretation are surprisingly adequate for highway work, since much of the work is in the nature of reconnaissance surveying and the results are construed to be approximations. The writer is careful not to risk interpretation on some special feature of the curve, since such features are usually due to random errors or lack of homogeneity among the subsurface strata. Effect of Surface Medium A resistivity depth sounding taken to a depth of 200 or 300 ft. is not much affected by superficial conditions, but these conditions have a great effect in depth soundings to 25 or 30 ft. In shallow soundings the character of the surface medium has a very marked effect on the entire resistivity graph. Fig. 1 illustrates a very striking example. Graphs A and B are depth soundings taken in approximately the same place. The surface stratum is a clay loam but at the place where graph B was taken

Jan 1, 1934

By H. N. Hall

Various factors must be considered in an engineering evaluation of gravity-drainage reservoirs. Among these are: (1) the effect of producing rate on total oil recovery; (2) the effect upon well productivity and ultimate recovery of the pressure level maintained during the producing life of the reservoir; (3) the economic advantage of full or partial pressure maintenance; and (4) estimate of the rate of gas production and injection and the possible purchase of gas under conditions of full pressure maintenance to ascertain compressor facilities needed. All of these factors can be evaluated only when a reliable method is employed for determining reservoir performance in gravity-drainage reservoirs. The purpose of this paper is to present a general method for calculating the performance of a gravity-drainage reservoir. This method is applicable for conditions of complete pressure maintenance, partial pressure maintenance and normal pressure depletion. Provisions are made to take into account variations throughout the reservoir of reservoir configuration, changes in permeability and fluid composition. Based on the method presented in this paper, an IBM 650 computer program has been developed. The past performance of an actual gravity-drainage reservoir producing under conditions of declining pressure and no gas injection was duplicated using this program. INTRODUCTION In tilted reservoirs the production of oil is influenced by drainage of oil from upstructure to downstructure locations. When this downstructure drainage of oil is sufficient to cause effective segregation of the gas and oil in a reservoir, the reservoir is usually classified as a segregation drive or gravity-drainage reservoir. (Discussion will be restricted to gravity-drainage reservoirs which have no encroachment of edge water.) The important feature in gravity-drainage reservoirs is the density difference between reservoir oil and gas. These phases tend to segregate in the reservoir with the result that in the gas cap the oil saturation is maintained at a higher level by drainage of oil from the gas-cap area. Oil can be produced from the oil zone at a low gas-oil ratio and reservoir energy is thereby conserved. The standard material balance in not adequate for predicting gravity-dramage reservoir performance because it does not take into account the difference in saturation above and below the gas-oil contact. Several authors'.' have presented methods for calculating the performance of gravity-drainage reservoirs in which reservoir pressure is maintained constant by gas injection into the gas cap. Using some simplifying assumptions, these methods can be employed with a desk calculator to give acceptable results. The problem of predicting the performance of gravity-drainage reservoirs under the conditions of declining reservoir pressure is many time more complex than that of constant pressure. fierefore, attempis to develop a method suitable for desk calculation have required excessively simplified assumptions. In the past several years, highspeed digital computers have become more widely available for reservoir engineering problems. These corn puters are well suited to problems such as the prediction of the performance of gravity-drainage reservoirs with pressure decline. Many of the simplifying assumptions necessary for hand computation can be eliminated so that a realistic approach to the gravity-drainage process can be made. CONCEPTUAL PICTURE OF OIL MOVEMENT IN GRAVITY-DRAINAGE RESERVOIRS Before attempting to develop an analytical treatment for conditions occuring in a gravity-drainage reservoir, a concept should be formed concerning the movement of fluids in the reservoir as oil is produced. A review of the literature'.' shows that it is customary to classify gravity-drainage operations into two categories—(1) with complete pressure maintenance, and (2) with declining pressure. The same line of reasoning will be followed in presenting the concept of the movement of fluids in the reservoir because it is easier to visualize the movement of fluids under conditions of complete pressure maintenance. After discussing complete pressure maintenance, an analogy will be made between that and the case of declining pressure. It should be kept in mind throughout that the final aim for the problem of solving gravity-drainage performance with digital computers will be to develop a general program for any kind of gravity-drainage reservoir. COMPLETE PRESSURE MAINTENANCE One feature which is generally common in gravity-drainage reservoirs is a gas cap located at the top of the structure. This is shown in Fig. 1(a). Fig. l(b) shows oil saturations that might occur through the reservoir. In the gas cap, oil saturation is lower than

By J. L. Huiatt, M. C. Fuerstenau, M. C. Kuhn

Dithiophosphatogen is the species responsible for flotation of pyrite when dithiophosphate is added as collector. Oxidation of collector apparently occurs by reaction with oxygen adsorbed on the pyrite surface. Oxidation of dithiophosphate and xanthate is also effected with Cu++, Cu(OH) , and Fe+++ and rates of oxidation are presented as a function of pH. Reasons for the selectivity observed when dithiophosphate is added as collector in a natural ore system as compared to xanthate are presented and discussed.

Jan 1, 1972

By Alexander Squire

One of the principal factors that have contributed to the hesitancy of design engineers to use metal-powder parts is the difficulty experienced in the determination of the mechanical properties of compacted components. Because standard test methods cannot usually be applied in the inspection of such parts, and because adequate special test methods have not been developed, it has been considered desirable to investigate the methods that are applicable. These may then be included in specifications for metal-powder materials and components in order that the design engineer may be assured that the subject parts possess the desired mechanical properties for satisfactory performance. It is known that direct relationships exist between usually nonmeasurable properties as tensile strength and elongation and shear strength and the angle through which compacts may be plastically deformed before fracturing. These correlations are valuable in the inspection of specific parts, but it is necessary to set up standards before they may be satisfactorily employed. Apart from the use of correlations, the number and character of the inspection methods that are applicable to almost all powder parts is limited to three—chemical analysis, density, and hardness. The last of these may or may not be a pertinent characteristic, since the indentation hardness of many powdeied-metal materials is so low as to have little significance. It is, however, occasionally desirable to use hardness measurements as an indication of the uniformity of the structure of pieces of a given type. Chemical analysis reveals very little about the physical properties of metal-powder compacts, since the unpressed powder is usually of a composition almost identical with that of the finished pieces. Density determinations are simple to perform and have the advantage of being nondestructive in character. If the dimensions of a machine part are known (and usually they are), the average density may be determined by weighing a given number of pieces and dividing by the calculated volume of the parts. More accurate measurements may be made by the water-displacement method. It is recognized that mechanical properties of metal-powder materials are related to their density, but usually these relations are determined for only one type of powder, processed under a given set of conditions. Comparisons of the pioperties of compacts formed from different types of powders are made on the basis of compacting pressures instead of density, and for this reason the results obtained by using powders of different types appear widely variant.

Jan 1, 1947

By Alexander Squire

One of the principal factors that have contributed to the hesitancy of design engineers to use metal-powder parts is the difficulty experienced in the determination of the mechanical properties of compacted components. Because standard test methods cannot usually be applied in the inspection of such parts, and because adequate special test methods have not been developed, it has been considered desirable to investigate the methods that are applicable. These may then be included in specifications for metal-powder materials and components in order that the design engineer may be assured that the subject parts possess the desired mechanical properties for satisfactory performance. It is known that direct relationships exist between usually nonmeasurable properties as tensile strength and elongation and shear strength and the angle through which compacts may be plastically deformed before fracturing. These correlations are valuable in the inspection of specific parts, but it is necessary to set up standards before they may be satisfactorily employed. Apart from the use of correlations, the number and character of the inspection methods that are applicable to almost all powder parts is limited to three—chemical analysis, density, and hardness. The last of these may or may not be a pertinent characteristic, since the indentation hardness of many powdeied-metal materials is so low as to have little significance. It is, however, occasionally desirable to use hardness measurements as an indication of the uniformity of the structure of pieces of a given type. Chemical analysis reveals very little about the physical properties of metal-powder compacts, since the unpressed powder is usually of a composition almost identical with that of the finished pieces. Density determinations are simple to perform and have the advantage of being nondestructive in character. If the dimensions of a machine part are known (and usually they are), the average density may be determined by weighing a given number of pieces and dividing by the calculated volume of the parts. More accurate measurements may be made by the water-displacement method. It is recognized that mechanical properties of metal-powder materials are related to their density, but usually these relations are determined for only one type of powder, processed under a given set of conditions. Comparisons of the pioperties of compacts formed from different types of powders are made on the basis of compacting pressures instead of density, and for this reason the results obtained by using powders of different types appear widely variant.

Jan 1, 1947

By L. D. Jaffe, R. K. Pitler

IT would clearly be advantageous to produce molten titanium, suitable for alloying and casting, directly from the relatively inexpensive tetra-chloride, without using a metallic reducing agent. Accordingly, a preliminary investigation has been made of the production of titanium by hydrogen reduction of the tetrachloride in an electric arc furnace. For the reaction: TiCl4(g) + 2H2(g) ? Ti(s) + 4HCl(g), Lockhart and his colleagues' have calculated equilibrium constants at 800" to 1500°K, based on tables of Brewer.' Extrapolating these data on the assumption that the heat of reaction varies linearly with temperature, and using Brewer's value for the heat of fusion, there is obtained for the reaction: TiCl4(g) + 2H2(g) ? Ti(l) + 4HCl(g) an equilibrium constant at 2100°K (100" above the melting point) Kp = (PHCl)4/pTlcl4 (Ph2)2 = 0.167 atm. If this is correct, starting with hydrogen saturated with TiC14 at 25°C, where the vapor pressure of the latter3 is 12.6 mm, and maintaining the overall pressure at 1 atm, 99 1/4 pct of the TiC14 would be reduced to Ti at equilibrium. An arc furnace designed for the melting of titanium and lined with water-cooled copper was used for the preliminary experimental check. Its inside diameter was 2 7/16 in. and height 6 in. The water-cooled electrode was tipped with 3/4 in. diam tung-sten. In the one run carried out, the furnace was charged with a starting batch of 293.35 g of scrap titanium,' analyzing 99.24 pct Ti. After the system was twice pumped out and flushed with argon to remove air, the arc was struck in argon and kept at 400 amp dc, electrode negative, for 1 min to melt the starting batch. Commercial tank hydrogen, dried by passing over silica gel and bubbled through technical grade TiC14 at room temperature, was then admitted to the furnace. The inlet tube directed this gas downward toward the arc and melt; the gas outlet was at the top of the furnace. The quantity of gas passed through was not measured accurately but is estimated to be about 50 liters per min at a few mm of mercury above atmospheric pressure. The arc was held in the H2-TiC14 mixture at 400 amp with little difficulty. After 10 min the arc burned through the copper lining above the melt, admitting water and ending the run. (This had happened frequently in straight melting runs under argon, and is not thought due to the atmosphere used.) In the furnace were found an ingot, several small pieces, and a little metallic powder, evidently formed when water entered the hot furnace. Some titanium also clung to the electrode. The portions were weighed and separately analyzed for titanium. Their total weight was 321.76 g of 94.82 pct overall purity. Much of the impurity consisted of tungsten broken off when the titanium was removed from the electrode. No detailed impurity analysis was made because the starting materials were impure and flooding the furnace introduced further contamination. Thus, the metal recovered contained 305.08 g Ti, as compared to 291.12 g in the starting batch. Titanium could not have been carried over from previous melting runs in the furnace, as the interior was sandblasted and the electrode ground clean before the run. Evidently at least 13.96 g of Ti were produced from TiCl4. Since this would require complete reduction of 430 liters of TiCl, gas at 12.6 mm of Hg, the efficiency of the process must have been rather high. Experimental work is continuing. No reason is seen why the process could not be scaled up to the size of a 30-ton steel-melting arc furnace. In a large unit there would be a large molten pool from which liquid metal could be withdrawn for alloying and casting. The problems of electrodes and power supply are similar to those arising in arc furnaces for melting titanium. Unreacted TiC14 and the HC1 in the exhaust gases could be recovered; unreacted H2 could be dried and re-used. The melt would be saturated with hydrogen, whose solubility in liquid titanium is unknown. Small amounts of hydrogen seem to have little effect on the properties of titanium.5 If the amount introduced was so large as to impair properties or cause casting difficulties, it could be reduced by holding the melt under an inert gas or by pumping on it, prior to casting. Acknowledgment The authors would like to thank I. Preble and M. Goldman for their valuable aid in the experimental work and the thermodynamic calculations, respectively. References 1R. J. Lockhart, J. J. Ward, M. J. Hussey, and J. W. Clegg: In unpublished report, "U. S. Air Force Project Rand. Titanium and Titanium Base Alloys." Battelle Memorial Institute (1949) 37-44. 2 L. Brewer et al: Chemistry and Metallurgy of Miscellaneous Materials—Thermodynamics. Ed. by L. L. Quill. pp 13-39, 60-192. (1950). McGraw-Hill Book Co. 3 K. Arii: Scientific Reports. Tohoku Imp. Univ. (1933) 22, 182. 4 R. S. Dean, J. R. Long, F. S. Wartman, and E. L. Anderson: Transactions AIME (1946) 166, 369-381; Metals Technology (Feb. 1946) TP 1961E. * R. I. Jaffee and I. E. Campbell: Transactions AIME (1949) 185, 646-654; Journal of Metals (Sept. 1949) TP 26813.

Jan 1, 1951

By P. T. Carter, A. B. Murad, H. B. Bell

N. A. Gokcen (Michigan College of Mining and Technology, Houghton, Mich.)—The activities of silica, represented in Fig. 5 for the systems MnO-SiO2 and CaO-SiO2, are in disagreement with the established binary phase diagrams. At Ns102 = 0.50 in MnO-SiO2, and at Ns102, = 0.65 in CaO-SiO2, each binary system is saturated with respect to silica at 1550°C, and therefore as102, is unity in each case. The curves for as102 (FeO-SiO2) and as102, (MnO-SiO,) should nearly co-

Jan 1, 1953

By H. R. Spedden, A. M. Gaudin, M. P. Corriveau

A preliminary study of silver ion adsorption by sphalerite in ion exchange column with influent electrolyte marked with radiosilver is described. Rapid ion exchange occurs at first followed by slow reaction controlled perhaps by solid state diffusion. One experiment with radiocopper instead of radiosilver is reported briefly. IT has been known for many years that sphalerite is floated after it has been activated by a metallic cation, particularly copper.' The activation of sphalerite by copper is known to be an exchange of an atom of copper for an atom of zinc at the surface of the sphalerite.2,3 It has been estimated from various guesses of the available mineral surface that the depth of the copper-bearing coating is of the order of thickness of one atom. However, the exact mechanism of the activation process is unknown. A number of metals other than copper act in the same general manner."' " In particular, it has been known that silver replaces zinc at the surface of sphalerite. As copper is usually divalent, whereas silver is monovalent, it may well be assumed that there are differences, perhaps major differences, in the detailed scheme of activation by these two cations. Furthermore, since silver has unusual photoelectric properties and may be a contributor to the fluorescence of sphalerite, a study of its activating mechanism might open up some interesting avenues for exploring these other phenomena. The choice of silver as an activator of sphalerite was suggested also by the fact that its radioactive tracer, silver 110, is particularly convenient in that it has a long half-life and is energetic enough to permit counting through a counter window. The experimental technique selected, therefore, included the preparation of solutions of silver nitrate con- taining a proportion of active silver nitrate sufficient to give convenient counting data. In further considering the method to be used, a desirable choice seemed the use of batch experimentation in which a given solution was allowed to act on a certain lot of mineral for a given length of time at a given temperature, this period of mutual reaction being followed by analyses of the separated solid and solution. But an alternative method seemed more attractive. This is the method now so familiar to the users of ion-exchange resins, which was first made famous by the Russian chromatographer, Tswett.6-8 It consists in forming the mineral into a porous column through which the solution is allowed to flow at a constant rate. The usual method of allowing a batch of solid to react with solution is the equivalent of a single plate distillation operation while the chromatographic or ion-exchange column is a multiple-plate method—the multiplicity of the plates being represented by the reciprocal of the rate of flow of solution through the column. It seemed to us that the chromatographic method had such

Jan 1, 1952

By Thomas C. Wilder

The activities of both components and the partial and integral molar thermodynamic properties of mixing for the liquid Al-Ge system at 1200°K and for the gertnanium-rich Al-Ge liquidus have been determined from data for eighteen alloys of compositions in the range 0.0593 < 0.880 using the reuersible gal-vanic. cell in the temperature interval 9320 to 1258°K. The liqui-dus compositions above 93 2 °K loere also ve determined by observing the discontinuities in the C us T plots for the high-melting alloys. This system shows moderate negative deviation from ideality throughout, the values for y° being 0.212 and 0.189 for aluminum and germanium, respectively, at 1200°K. Pavtial molar Properties of aluminum on the germanium-rich solidus and at infinite dilution in Ge(s) oboue 932°K were estimated from the foregozng measurements and the equlibrium data of previous investzgators. RECENT compilations of data1" have shown an increasing demand for knowledge of the thermodynamic properties of mixing of metallic alloy systems. In the case of binary-liquid systems where one of the components is a semiconductor this information is useful because, primarily, properties of the second (dopant) component on the liquidus, solidus, and at infinite dilution may be determined more accurately than from calculations based on the phase diagram. In this investigation a reversible galvanic cell was used to determine the chemical potential of aluminum in the two-phase region, liquid + [Ge], on the germanium-rich side of the A1-Ge system in the temperature range 932" to 1193°K. In addition, similar measurements for homogeneous liquid A1-Ge alloys for the entire composition range were obtained for the temperature interval 932" to 1258°K. The cell used was: The experimental technique and the treatment of the data were essentially the same as described earlier394 and are elaborated upon only briefly here. Each cell consisted of a liquid aluminum anode and three A1-Ge alloy cathodes of different composition which were held in Morganite alumina crucibles. The alloys were made up from aluminum and germanium weighed to the nearest 0.1 mg to a total weight of 5 to 10 g. Aluminum was a gift of Aluminum Co. of America and had a purity of 99.995+ pct. Germanium of transistor grade was a gift of Bell Telephone Laboratories. The four electrodes were contained in a larger alumina crucible which also held the prepurified fused chloride electrolyte. Contact to the electrodes was made by tantalum wire leads sheathed in alumina. The tantalum leads were centered in the electrodes by suitable positioning of an alumina radiation shield which fitted on the top of the - alulnina crucible. Two chrome l-alumel thermocouples, sheathed in quartz wells, completed the internal cell arrangement. The entire assembly was enclosed in an alumina tube, fitted with a water-cooled copper head so the system could be evacuated and then flushed with purified argon. *

Jan 1, 1967

By G. Pizzi, G. M. Ciucci, G. L. Chierici

The use of the material balance equation to estimate the volume of hydrocarbons originally present in a reservoir, whose producing mechanism is partly due to water drive, has been discussed in the literature by several authors. There is no general agreement upon the possibility of obtaining reliable results by this method. Gas reservoirs in contact with an active aquifer are considered in this paper. Theoretical considerations based on the cybernetic principle of uncertainty (which states that the internal structure of a system cannot be uniquely determined from its observed external behavior) lead to the conclusion that the volume of gas originally present in a reservoir of this type cannot be uniquely determined from its past history. The range of values which encompasses the actual value of the reserves varies from case to case and must be determined by either numerical or analogical methods. Results obtained for six gas fields are reported. All these fields were produced with small fluctuations in their production rates, as is common practice for gas reservoirs; no gas storage fields were considered. Results obtained show that reserves values in a range of 1 to 2, associated with appropriate aquifers, allow the matching of the reservoir past history with mean-square deviations less than the experimental errors involved in pressure and produclion measurements. Similar results have been found in several other partial water drive gas reservoirs. From these results it is concluded that gas reserves cannot be uniquely determined from the past performance of partial water drive reservoirs, at least in cases where the reservoir has been submitted to small fluctuations in the production rates, and pressure data of normal accuracy are available. INTRODUCTION A number of authors have analyzed the problem of estimating the reserves originally present in a partial water drive reservoir from its past pressure-production performance. Literature which deals with this subject can be grouped, according to their conclusions, as follows. 1. A reliable value for the reserves can be obtained even if reservoir data (pressure and cumulative production) are affected by errors within the normal range.&apos;-&apos; 2. A reliable value for the reserves can be obtained only if reservoir data are very accurate&apos;- or if past production performance has been subjected to abrupt variations in the production rate."&apos; 3. No unique value for the reserves can be obtained from reservoir past production performance. This conclusion has been based upon theoretical considerations" and verified in several field cases. The purpose of this paper, which deals only with partial water drive gas reservoirs, is to test the above conclusions against actual field cases. Some theoretical considerations on this problem are also presented. THEORETICAL CONSIDERATIONS As the behavior of a gas reservoir communicating with an aquifer depends on both the aquifer and the reservoir characteristics, the physical system to be studied is the combined gas reservoir plus aquifer. The information which is available for studying the performance of such a system is the well production rates and bottom-hole pressures, all given as functions of time. The external behavior of the reservoir-aquifer system is therefore described by 2n input variables (Gp, Wp,) and n output variables (p,), n being the number of wells in the reservoir. In reservoir engineering it is common practice to consider the reservoir as a whole, disregarding the internal distribution of pressures and of producing wells. This practice is equivalent to substituting the above multi-variable system with a single-variable system, where the average reservoir pressure is the only output variable and the cumulative production G,(t) and W,(t) are the input variables. The internal structure of such a system, defined by initial gas reserves G, aquifer shape and dimensions, boundary conditions and petrophysical parameters distribution throughout the aquifer, is unknown. Therefore, from a cybernetic point of view the system is a "black-box It has been demonstrated" that for a blackbox the indetermination principle holds. Accordingly, the number of different internal structures (or set of parameters) which can account for the observed external behavior is infinite. As a consequence, the initial reserves cannot be uniquely determined from the reservoir past performance. When W,(t) is known, the determination of G from

By H. J. Gluiskoter

The chlorine content of the coals in the Illinois Basin ranges from 0.00% to more than 0.60%. The chlorine content of the Herrin (No. 6) Coal has been mapped on a regional scale and, in general, increases with the depth of the coal. The depth-chlorine correlation exists because the coal is in apparent equilibrium with the composition of the ground water associated with it, and the salinity of the ground water generally increases with depth. At least part of the chlorine can be easily removed from the coal in the laboratory. In a natural weathering experiment, chlorine values decreased markedly during an 8-week period. Results to date indicate that none of the coals studied has a sufficiently high chlorine content to make it unusable in high-temperature steam boilers, although special steps may be necessary in the preparation or utilization of some of the highest chlorine coals. Investigations into the occurrence and distribution of chlorine in Illinois coals have been in progress at the Illinois State Geological Survey for over 35 years. Since 1948, chlorine analyses of face channel samples and of drill core samples of coal have been made routinely. The increased interest in chlorine and alkalies in coal in the U.S. followed that in Europe, where power plants during World War II were called upon to produce at higher levels than previously and with less down time for maintenance. Higher steam temperatures were reached, resulting in increases in the amount of fouling of external heating surfaces and in corrosion of boiler tubes when high chlorine coals were used. Early studies of the problem showed that coals with high chlorine content were more likely than those low in chlorine to cause difficulties in installations fired with powdered fuel. Crossleyl reported that the first rule of thumb developed for British coals was that coals considered to be high in chlorine (more than 0.30%) caused the most trouble, those intermediate in chlorine content (0.15% to 0.30%) were less likely to cause difficulties and those low in chlorine (less than 0.15%) generally were not associated with alkali bonded deposits and corrosion. However, this relatively simple picture was not adequate to characterize the difficulties that could be expected during the utilization of a large number of coals and Crossley1 developed another scheme for assessing the chances of superheater corrosion. This scheme took into consideration the observation that coals high in sulfur as well as chlorine are more likely to cause corrosion and fouling than coals low in sulfur and high in chlorine. Crossley also considered the ash content. When two coals had the same chlorine and sulfur contents, the one with the greater amount of ash would be the less likely to cause difficulties. Knowing only the amount of chlorine in a coal obviously will not give all the answers. Indeed, the significance of the chlorine content has been much discussed and it has been suggested that perhaps the total alkalies are a better indicator of possible troubles. The observation that the deposits that form

Jan 1, 1968

By M. C. Chang, J. Dasher

The Crucible mine in Pennsylvania, operating on Pittsburgh seam coal, is rated at 5000 tpd. The washing plant, built in 1943, is rated at about 400 tph, using hydroseparator boxes to wash the coarse coal (4 x 5/16 in.) and hydrotator units for the fine coal (5/16 x 0). It is generally acknowledged that gravity concentration equipment cannot be used efficiently to bene-ficiate coal finer than about 65 mesh. Before the present flotation circuit was installed, Crucible recovered its fine coal slurry, predominantly —24 mesh material, by passing it through a battery of five 14-in. and one hundred and ten 3-in. Hey1 & Patterson cyclones in parallel with a 75-ft Dorr thickener. About two thirds went to the cyclones and one third to the thickener. Underflows from cyclones and thickener were filtered, respectively, in one 12-disk Eimco and two 4-disk Oliver filters fitted with stainless steel cloth. The resulting cakes were added to the coarse metallurgical coal. The filtrates, overflow from the 3-in. cyclones, and thickener overflow were recycled to the coarse coal plant. The three major problems encountered in this system became acute when the mine switched from track-mounted machinery to the more economical off-track equipment. The quality and uniformity of product declined, too much slime accumulated in the circuit, and waste pond disposal became highly impracticable. Lowering of Quality and Uniformity: Since the filter cake was not beneficiated in any way, addition of this material, which contained about 18 pct ash. would certainly lower the quality of metallurgical coal. Difficulties of handling the high-ash, high-moisture cake were compounded by the lack of adequate blending facilities at the mine, making it impossible to maintain uniform feed for the coke ovens. For a two-month test period, to verify the source of trouble, all filter cake was excluded from the metallurgical coal. The excluded filter cake was stocked in the yard. Slime Buildup: The moisture retained in the coarse coal products and the filter cake provided daily the only means of slime bleed from the circuit. As this bleed was not enough to offset the incoming fines in the raw coal feed, there was excessive buildup of slimes. To operate at all, it was necessary to purge the system each weekend by pumping all the solids from the thickener to a waste pond. The slimes built up during the week progressively increased the apparent viscosity and density of the circulating plant water, so that hydroseparators and hydrotator units had to be constantly adjusted. Uniformity, yield, and quality of the metallurgical coal suffered in consequence, and the filter cake ash and moisture contents increased from Monday to Friday. Limited Waste Disposal: Location of the plant does not permit unlimited waste pond area. Maintenance of a waste pond for the purpose of emptying the thickener during weekends became a costly burden that could not be tolerated. HOW THE PROBLEMS WERE SOLVED The flowsheet (Fig. 1) chosen to overcome these difficulties is considered the one most economical to install and operate. In a preliminary change made before the flotation circuit was installed, the cyclones and thickener were first operated in series, the overflow from the 3-in. cyclones, after flocculation, being discharged into the thickener and the thick-

Jan 1, 1960

By T. M. Geffen, R. E. Gladfelter

Lipson1 has recently presented a technical note wherein theoretical considerations were used to demonstrate. that the adsorption us saturation relation for a linear absorption method is not necessarily a single valued function of saturation.1 It was concluded that the absorption us saturation relationship is subject to the same hysteretic effect as is the flow behavior between the drainage and imbibition systems. It is the purpose of this note to show, by experimental results, that for the manner in which fluids are distributed in porous materials during fluid flow, the relative X-ray absorption us saturation relationship is single-valued regardless of the saturation history. The design of the apparatus used to measure relative X-ray absorption of cores undergoing fluid flow tests is similar to that described by Morgan, McDowell and Doty. A few modifications have been incorporated in the design to increase sensitivity and simplicity of measurement. The sensitivity is such that for usual types of cores a recording pen movement of approximately 12 linear in. is occasioned between the recording of the core dry and when it is completely full of an absorbing liquid, a solution of approximately five per cent by volume of iodo-benzene in a close-cut hydrocarbon fraction, or a solution of 50,000 ppm sodium iodide in water. Two types of experiments were conducted, one in which the liquid was inside the core, and the other with the liquid outside the core. Tests with the liquid inside the core were run to cover the saturation range encountered in both the drainage (gas drive) and imbibition (liquid flood) flow systems. It is pointed out that the same core was used, but the tests were conducted at different times with the recording mechanism balanced at a different position. Therefore, the absolute values of relative X-ray intensity at any saturation are not the same in each test. In the second type of test the same core was used, but this time its pore space cmtained only gas, and various thicknesses of oil contained in plastic cells were placed in front of the dry core. As before. the relative X-ray ah- sorption was measured and compared to the quantity of oil in front of the core. The arrangement of the fluids with respect to the path of X-rays in these two types of tests represent fluid distributions of a wider difference than can be expected between that established in a core just due to imbibition and drainage saturation flow histories. Thus any deviation from a straight line relationship of the log of the relative X-ray intensity us saturation calibration should be readily apparent. Results of the laboratory tests are given in Fig. 1. A schematic diagram showing the position of the fluids with respect to the path of the X-ray beam is given for the two cases investigated. In the case where the oil existed outside the core (Case B), the log of the X-ray intensity (log, I/I,) is related directly to the cell thickness (amount of oil in X-ray beam path). This correlation is in full agreement with X-ray theory. In the case where the oil or water existed inside the core (Case A) which covers both drainage and imbibition types of flow processes, again the relationship between absorption and saturation (amount of oil in X-ray beam path

Jan 1, 1952

By J. Campbell

Various models are discussed for the evaluation of the negative pressures which may occur in solidifying materials which exhibit various deformation modes: elastic-plastic, Bingham, viscous, or creep flow. The inadequacy of the previously proposed elastic-plastic solution for solidifying metals is revealed by comparison with the more reliable creep results which are given graphically for aluminum, copper, nickel, and iron. The maximum tensions experienced in the liquid phase of solidifying spheres ranging in size from large castings to submicron powders are in the range from —10&apos; to —105 atm for these metals. THERE has been much recent interest in the negative pressures associated with the volume change on solidification and in the possibility of the occurrence of cavitation. Considering the freezing of a highly supercooled liquid, an attempt to evaluate the stresses in the liquid ahead of the rapidly moving solidification front has been made by Horvay1 on a microscale and by Glicksman2 on a macroscale. In a casting of a wide freezing range alloy, the pressure differential due to viscous flow of residual liquid through the pasty zone has been discussed by Piwonka and Flemings,3 In a previous publication4 the author has attempted to estimate the negative pressure occurring in the residual liquid of a spherical casting, employing an elastic-plastic model to describe the collapse of the solidified shell under the internal tension. An earlier model assuming a rigid shell was shown to be inaccurate by many orders of magnitude. The elastic-plastic model is critically reviewed here, and other models are developed which are thought to be more closely related to metals and other materials near their melting points. The spherical geometry (Fig. 1) is chosen because the highest shrinkage pressures would be developed, although the analyses are readily adaptable to cylindrical geometry. A parallel sided casting experiences little internal tension because of the relatively easy dishing inward of the sides. (This commonly observed phenomenon has previously been attributed solely to atmospheric pressure.) Furthermore, small regions of confined liquid in a large solidified volume of a casting approximate reasonably well to spherical geometry. ELASTIC-PLASTIC MODEL The author has shown4 that as solidification proceeds the internal hydrostatic tension builds up until the elastic limit of the shell is exceeded. At this point the internal pressure is closely -2Y/3. Subsequently a plastic zone spreads from the inner surface toward the outer surface of the shell. When the whole casting is deforming plastically a rather more generalized analysis taking account of the externally applied pressure PA + 2y/b gives the internal pressure as: P = Pa + 2y/a + 2ys/b - 2 Y In(b/a) [1] The 2y/a and 2ys/b terms result from the tendency of the liquid-solid and solid-vapor interfaces to shrink, reducing their energy, and thereby helping to collapse the solid phase and compress the liquid phase. The 2y/b term would be important only for powders. The last term arises because of the plastic restraint of the solid, resisting collapse and so effectively expanding the residual liquid. From Eq. [I] it is easily shown that there is a minimum in the pressure at the radius amia= y/Y [2] which is of the order of 103K for the metals aluminum, copper, and iron, and corresponds to the minimum pressure Pmin = 2 Y[l-ln(bY/y [3] The results of a fully worked out elastic-plastic solution are given in a previous reporL4 The main criticism which may be leveled at this analysis when applied to metals at their melting points is the strong dependence of the yield stress on the strain rate. The strain rate varies with both solidification conditions (e.g., whether chill-cast or slowly cooled) and during solidification, as is indicated in the following section. Thus an appropriate choice of Y is very arbitrary. Before proceeding to a discussion of models which are strain-rate-dependent, it is necessary to evaluate the strain rate as a function of the rate of solidification. SOLIDIFICATION RATE Various empirical relations have been deduced5 for the rate of thickening of the solid shell by pour- out tests on partially solidified spheres. These, however, are unsatisfactory for our purposes since they become very inaccurate when the liquid core is very small. A theoretical approach is therefore necessary, and some solutions are set out below. Making the assumptions of constant surface temperature of the casting during freezing, no superheat, and a material freezing at a single temperature, Adams8 deduces the approximate solution: which becomes when b » a: Employing a semiempirical approach vallet6 finds:

Jan 1, 1969