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By Irving Cadoff, Kurt Komarek, Edward Miller

THE lead-telluride phase diagram as compiled by ansen' has one intermetallic compound, PbTe, with solid-solubility limits extending from 22 to 45 wt pct Te (31.4 to 57.1 at. pct). Pelzel2 redetermined the solubility limits on the lead-rich side of the compound by measuring the relative areas of the two phases in samples annealed in the liquid + compound region, and obtained data that agreed with that of Hansen. Recent studies of the semiconducting properties of PbTe3 however, have indicated that addition of either lead or tellurium to PbTe does not produce samples having carrier concentrations greater than about 10 19 cm-3. Assuming that each impurity atom results in one ionized charge carrier, this carrier concentration corresponds to a solubility range of less than 0.04 at. pct. Fritts and Karrar4 have also observed two phases in samples containing from 0.15 to 3.0 pct excess Pb. To resolve the discrepancy between these data, the solid solubility limits of the compound PbTe were reinvestigated, using several other techniques. Ten 25-g samples with compositions of 1/2, 1, 3, 5, and 10 wt pct excess Pb and Te and two 100-g samples of 15 and 65 wt pct Te were prepared, sealed in evacuated quartz capsules, and melted at 950oC. The 1 pct excess Pb and Te and the 15 and 65 wt pct Te alloys were homogenized for 96 hr at 450°C; the remaining specimens were annealed 50°C below the solidus temperature reported in Hansen. The specimens were polished and etched with dilute HNO,. All the samples were two phase, the second phase appearing at grain boundaries or as spheroidized inclusions in the grains. In the case of the tellurium rich specimens, the second phase could be identified as a eutectic. Debye-Scherrer powder diffraction patterns of the i, 1, 3, 5, and 10 pct excess samples were obtained using CuKa filtered radiation. The films were indexed as the B1 or NaCl structure. The calculated lattice parameter of PbTe was the same for all the specimens, with an average of a0 = 6.460 ± 0.0005A. Lines due to excess lead or tellurium were very faint but could be clearly seen in all the films. The relative areas of the two phases in the 15 and 65 wt pct Te samples were corrected for the differences in density of Pb, Te, and PbTe, and taken as proportional to the relative volumes of the two phases. The corrected relative volumes agreed with a phase diagram having negligible solubility of both lead and tellurium in lead tellurium. The density of the two specimens was obtained to give a third independent determination of the phase limits. The specimens were broken into small pieces to eliminate any internal porosity, and adherent air bubbles were removed by vigorous shaking under water for several hours. The density of lead (11.34 g per cm3) and of tellurium (6.25 g per cm3) was taken from the International Critical Tables and that of stoichiometric PbTe (8.25 g per cm3) calculated from the lattice parameter. For the 15 wt pct Te samples, the density assuming no solubility was calculated to be 9.89 g per cm3; the observed density was 9.86 g per cm8. For the 65 wt pct Te alloy, the density calculated for the case of no solubility was 7.24 g per cm3; the measured density wag 7.22 g per cm3. These results are consistent with those of planimetry and X-ray. SUMMARY Data have been presented which show that the solid solubility of both lead and tellurium in PbTe is

Jan 1, 1961

By T. A. Griffin

Surface mining today is faced with a twin challenge: (1) accelerating the rate of removal of massive quantities of overburden and ore, and (2) replacing comparable high volumes of overburden in the mined-out portion of the pit. It is against this background, coupled with increased demands for fossil fuels worldwide and legitimate environmental concerns, that the role of bucketwheel excavators and reclaimers has been raised to new prominence.

Jan 10, 1974

By C. E. Lesher

COAL has been fighting a rear-guard action since the last World War. The battle against competitive fuels has been largely guerilla warfare with more sniping within the ranks than of organized opposition. Oil and natural gas are the fuels that over these twenty odd years have driven coal backward and out of many profitable markets. Now, somewhat timidly, the coal industry is trying a new weapon; namely, Research, or let us more properly say, Organized Research. Engineers have been designing this weapon for many years, supported by those interested in coal, including some coal producers. A part of this pioneer work has been Fundamental Research, the Ph.D. kind that is over the heads .of most of us. Another part has been aimed at immediate objectives and realizable profits, the practical, man-in-the-street sort. That is Industrial Research. Enough has been accomplished to make a fair exhibit, but whether this new weapon will have sufficient fire power to rout the opposition, whether the industry will really go into production and use it, the next few years will tell. NEED FOR COAL RESEARCH To utter "Research" is to use the modern magic word; to conjure up the miraculous-rubber from weeds; radar; magnesium from sea water; yes, even gasoline from coal. Research is a very general term. It means something different to every man. What is the coal industry seeking with its research; or what should it seek? And, specifically, how is it going about the job; and is it taking the best way? There are many who say that Coal has been asleep at the switch, while Oil and Gas have been taking the energy business. In an organized way this is true. Large-scale, privately financed research is just started in the Pennsylvania, anthracite industry, and it is still a dream for bituminous coal. What has been done so far collectively is purely defensive; as, for instance, to improve mechanical devices for burning coal so as to be able to recover markets for house-heating fuel long since abandoned to oil and gas. To appreciate just how seriously bituminous coal has slipped back in the national economy in the past 25 years, one has only to recall that, in the last war the Navy required for its operations all the high-grade, low-volatile coal that could be produced, and that anthracite was withdrawn from the middle and northwest markets to keep the eastern seaboard warm. All coal was "rationed" by zones, if not to individuals. Now the Navy, the Armed forces and the Merchant Marine are propelled by oil and gasoline. Gasoline and heating oil are rationed to individuals. Production of all coal in this country in 1918 reached the historic figure of 678,200, 000 tons, and in 1943, after 25 years, it is expected to reach a special wartime total of 660,000,000 tons. Meanwhile, production of crude oil this year may exceed 1,500,000,000 bbl., and like that of natural gas, reach four times the amount produced in 1918.

Jan 1, 1944

By Mrs. V. J. DeCarlo, G. P. Salvo, H. W. Schadler, L. M. Osika

The lattice parameter of the inlerrnetallic compound Nb3Sn has been measured as a function of temperature from 80° to 1290°K. The results are compared with published data on the thermal ex- ThE recent interest in the intermetallic compound, Nb3Sn, as an engineering material for the production of superconducting devices has necessitated that certain engineering data be obtained. Because of the difficulty encountered in producing bulk pansion of niobium and indicate that the compound when made by diffusion of tin into niobium at 1000°C, would be subjected to a tensile strain of about 0.1 pct when cooled to room temperature. material which is single phase, the coefficient of thermal expansion has not been measured by dilata-tional methods. Therefore the lattice parameters of fine-grained samples of Nb3Sn produced on the surface of a niobium sheet by heating in molten tin at 950°C have been obtained as a function of temperature. The results are compared with published data on niobium2 and Nb3Sn3 and with lattice-parameter measurements made on small single crystals of Nb3Sn.

Jan 1, 1964

By Gray L. L., Max Littlefield, Godbold A. C.

The West Edmond pool of Central Oklahoma, a limestone reservoir, has an area in excess of 29,000 acres and as of Sept. 15, 1946, had produced 53 million barrels of oil from 731 wells at an average depth of 6900 ft. Water has encroached into the reservoir along the west side of the pool and although the area of water invasion is large the net volume of water influx is small, because encroachment has been primarily into a fracture system. The most significant part of this study concerns the character of the Hunton reservoir. Geological study of cores of the producing section was made to supplement core-analysis data. It was determined that approximately 90 pct of the pore volume was contained in intergranular or sand-like porosity and 10 pct in fractures (intermediate porosity). The porous limestone is divided into blocks by the fractures, although in the strongly dolomitic parts of the producing section, fractures are less well developed. The low-permeability intergranular porosity, largely subsidiary to the high-permeability fractures, will produce oil into the fractures by evolution of solution gas. The fractures in effect serve as drainage channels for production of oil from the inter-granular porosity. Because of such a large difference in permeabilities of the two com-ponents, a high degree of by-passing will occur, and, accordingly, the economics involved in undertaking full-scale high pressure gas injection operations have been seriously questioned. Introduction The West Edmond Hunton pool, which covers portions of Canadian, Logan, Oklahoma, and Kingfisher Counties in Central Oklahoma, is the largest reservoir producing oil from a limestone in the state. The total area of the pool comprises about 29,240 acres and development is considered to be essentially complete. In all, 731 producing wells have been completed in the Hunton reservoir at an average depth of approximately 6900 ft, and have yielded a cumulative oil production in excess of 53 million barrels as of Sept. 15, 1946. In addition to wells completed in the Hunton limestone, 21 wells have been completed in the Bartlesville sand at a depth of approximately 6500 ft, which have produced a total of 730,000 bbl of oil. One small producer has been completed in the Cleveland sand at a depth of 5700 ft. However, a study of only the Hunton limestone reservoir will be presented in this paper. The most significant phase of this study concerns the special type of geological core examination that was made in an effort to ascertain the type and degree of porosity in the rock in accordance with lithologic types. Results of this geological study showed the west Edmond pool to be of such a complex nature as to appreciably affect the behavior normally associated with homogeneous reservoirs. Recognition of this condition in the

Jan 1, 1948

By Max Littlefield, Godbold A. C., Gray L. L.

The West Edmond pool of Central Oklahoma, a limestone reservoir, has an area in excess of 29,000 acres and as of Sept. 15, 1946, had produced 53 million barrels of oil from 731 wells at an average depth of 6900 ft. Water has encroached into the reservoir along the west side of the pool and although the area of water invasion is large the net volume of water influx is small, because encroachment has been primarily into a fracture system. The most significant part of this study concerns the character of the Hunton reservoir. Geological study of cores of the producing section was made to supplement core-analysis data. It was determined that approximately 90 pct of the pore volume was contained in intergranular or sand-like porosity and 10 pct in fractures (intermediate porosity). The porous limestone is divided into blocks by the fractures, although in the strongly dolomitic parts of the producing section, fractures are less well developed. The low-permeability intergranular porosity, largely subsidiary to the high-permeability fractures, will produce oil into the fractures by evolution of solution gas. The fractures in effect serve as drainage channels for production of oil from the inter-granular porosity. Because of such a large difference in permeabilities of the two com-ponents, a high degree of by-passing will occur, and, accordingly, the economics involved in undertaking full-scale high pressure gas injection operations have been seriously questioned. Introduction The West Edmond Hunton pool, which covers portions of Canadian, Logan, Oklahoma, and Kingfisher Counties in Central Oklahoma, is the largest reservoir producing oil from a limestone in the state. The total area of the pool comprises about 29,240 acres and development is considered to be essentially complete. In all, 731 producing wells have been completed in the Hunton reservoir at an average depth of approximately 6900 ft, and have yielded a cumulative oil production in excess of 53 million barrels as of Sept. 15, 1946. In addition to wells completed in the Hunton limestone, 21 wells have been completed in the Bartlesville sand at a depth of approximately 6500 ft, which have produced a total of 730,000 bbl of oil. One small producer has been completed in the Cleveland sand at a depth of 5700 ft. However, a study of only the Hunton limestone reservoir will be presented in this paper. The most significant phase of this study concerns the special type of geological core examination that was made in an effort to ascertain the type and degree of porosity in the rock in accordance with lithologic types. Results of this geological study showed the west Edmond pool to be of such a complex nature as to appreciably affect the behavior normally associated with homogeneous reservoirs. Recognition of this condition in the

Jan 1, 1948

By G. Derge, Ling Yang, John Henderson

Self-diffusion coefficients of aluminum have been measured by the capillary reservoir technique in liquids of the CaO-SiO2-Al2O3 system containirg equimolar portions of CaO and SiO2, in the temperature range 1400o to 1520oC. For the melt containing 6.0 mole pct Al2O3 the results can be expressed by the equation D = [(4.3 * 0.3) x 104] exp [(-85,000 * 17,500)/RT]cm~sec-'; for the melt containing 12.5 mole pct Al2O3, by the equation D = (5.4 i 0.2) exp [(-60,000 * 10,00O)/RT] cm2sec-: A concept of the constitution of these melts has been developed which proposes that the ratios O/(Si +Al) and Al2 O3/CaO determine the dominant species present. In recent years considerable work has been done on the system CaO-SiO2-A12O3 with a view to elucidating the structure of liquids of this system. Conductivity,' electromotive force, 3 density,4 and activity5 measurements have all contributed to an understanding of the problem, but as yet there is no entirely satisfactory theory that can account for all the observed experimental results. In principle, measurements of self-diffusion coefficients should give further information which is not obtainable in other ways. Self-diffusion coefficients for calcium, silicon,6 and oxygen7 have been measured. The present investigation extends the series of self-diffusion coefficient measurements to include aluminum and develops a concept of constitution for liquids of this system which is compatible with all the observed experimental results. EXPERIMENTAL The technique used in the measurement of the self-diffusion coefficient of aluminum was the capillary-reservoir method,8 A126 being incorporated in the melt contained in the capillary and inactive aluminum in the reservoir melt. This method was chosen because it minimizes convection currents' in the diffusion zone. It has the further advantage that the boundary conditions are such that a slight modifica- tion of Anderson and saddington's8 solution of Fick's Law yields an equation which requires measurements only of the length and the initial and final average specific activities of the solidified melt within the capillary. where t is the diffusion time, Co is the average specific activity of the melt contained in the capillary at t = O, C is the average specific activity of the melt contained in the capillary at t = t, 1is the length of the capillary, and D is the self-diffusion coefficient. The equation is of somewhat different form than those previously applied to high temperature diffusion studies because the specific activity of the melt in the reservoir was negligible both before and after diffusion. The diffusion apparatus is shown schematically in Fig. 1. It consisted of a silicon carbide resistance furnace containing the inactive melt in a graphite crucible, internal dimensions 7/8 by 4 in., enclosed in a 1 1/4- by 1 1/2- by 30-in. McDanel tube. A 3/8-in. McDanel thermocouple sheath to which graphite radiation shields and a graphite protection tube were affixed, was used to hold the capillaries. By moving this sheath through a rubber seal at the top of the McDanel tube the capillaries could be lowered into or raised out of the melt. Temperature was measured with a Pt-Pt 13 pct Rh thermocouple which was calibrated periodically against a standard couple. The furnace temperature was controlled to ± 5°C through the thermocouple immersed in the melt. Temperature variation over the depth of the melt was less than ± 3°C. The inactive melts were prepared from pure native quartz, assaying better than 99.9 pct SiO2, A.R. grade A12O3 and A.R. grade CaCO,. The same quartz and CaCO3 were used in preparing the active melts, the

Jan 1, 1962

By Frank D. Hoyt

BY far the most conspicuous of the Pennsylvania slate districts is that extending from the New Jersey line at the Delaware Water Gap westward almost to the Schuylkill River. This covers parts of three counties in east-central Pennsylvania: Northampton, Lehigh, and Berks. The most important development, both in geographic size and product importance, is in Lehigh and Northampton counties. The greater part of the region is underlain by only one formation-the Martinsburg, consisting of slates, clay slates, and sandy shales, all of the Ordovician period. The slate-bearing Martinsburg formation is underlain by Cambro-Ordovician limestones. Immediately overlying the Martinsburg formation is the Tuscarora quartzite of the Silurian period. The Martinsburg formation itself is divided into three distinct divisions, termed simply: the upper, the middle, and the lower members. Commercial slate has been extracted from all of these members, but the formation of greatest importance is the upper member, representing 2600 ft of the total formation thickness of nearly 11,000 ft. The upper member is commonly referred to as the "soft slate" and consists of three facies: 1) beds of blue-gray, very sandy, almost quartzitic slate, in many places, approximately a medium-coarse sand- stone with calcareous cement; 2) blue-gray sericitic slat-the dominant rock type of this member-with occasional chloritic beds; and 3) dark gray or virtually black, highly carbonaceous beds, referred to locally as "ribbons."

Jan 8, 1958

By T. S. Spice, H. L. Lovell, R. W. Utley

With the increased demand for lightweight aggregate, such materials have been manufactured from slags, clays, slates and, to a minor extent, the refuse of coal preparation processes. The latter source is attractive due to current interest in eliminating air pollution and improving the unsightly appearance of refuse piles as well as potential economic advantages, if a satisfactory product can be manufactured. A study has been made relating the composition of coal refuse, expressed as washability data, and the properties of a resulting aggregate. Three different refuse samples (bituminous and anthracite) were separated at gravities ranging from 1.4 to 2.96. Their chemical composition was determined. Aggregates were prepared in the laboratory from these fractions before and after ashing, at temperatures between 1250' and 1350°C. The specific gravity, expansion and compressive strength of the products were measured. The response of the refuse to bloat is related to the chemical composition of the ash to yield a glass of desirable viscosity and to the presence of a material which will form a gas in the appropriate temperature range. Carbonaceous material within the particle is a negative factor since after the glassy phase forms, oxygen cannot enter the mass thus inhibiting bloating. Precombustion of the refuse is also detrimental since it removes substances of gas-forming capability. The fraction sinking at 2.60 yielded an aggregate which had the lowest specific gravity, greatest expansion and greatest compressive strength. The purpose of this study was to seek and evaluate possible relationships between the composition of coal refuse, as expressed by washability data and factors affecting the production of a lightweight aggregate from refuse by bloating. The study was related to an intense program in the Department of Mineral Preparation at the Pennsyl- vania State University to study the possible elimination of air pollution from coal refuse fires by producing a low-carbon secondary refuse. Another phase of this program is considering possible uses of such a secondary refuse. Thus one study was to determine if a lightweight aggregate could be produced from this new refuse material and what effect the nature of refuse beneficiation would have upon the characteristics of a commercial aggregate product. It was hoped that these studies would assist in the design of a process and in establishing the optimum specific gravities at which refuse separation could be made in respect to the production of a low grade fuel from the float product and a raw material for lightweight aggregate from the sink product. The combination of producing a saleable low grade fuel and a lightweight aggregate, while at the same time minimizing disposal costs and air pollution contributions would be attractive to the coal mining industry. MECHANISM OF BLOATING Austin, Nunes and Sullivan,1 Ehlers,3 Everhart, 4 Riley7 and others, have stated that bloating is an expansion process in which two essential conditions exist simultaneously. These are: the development of a glassy phase over a relatively wide temperature range (the viscosity of this glassy phase plays a major role in the retention of the evolved gases) and the evolution of gases (SO2, SO3, CO2 and O2) from mineral decomposition in sufficient quantities at appropriate temperatures to form a cellular structure in the mass. Unless these two "type" reactions take place at the same time or in overlapping ranges of time and temperature, cellulation will not occur. In this event, the gas will escape or the melt will be too fluid to retain it; or if retained, the cells may be too large or the walls too thin for good strength in the product. The stages that occur when clays and shales are heated in an oxidizing atmosphere may be summarized as follows: 1) Drying and removal of free water to 200°C. 2) Absorbed water dehydration period (200 to 480°C). 3) Chemically-combined water dehydration period (480 to 700°C).

Jan 1, 1965

By Erminio Ferraris

The development of the mining industry in Sardinia dates from the application of the mining law of 1859, which, following the example of the French mining law of 1810, declared prospecting to be free, and suppressed the liens which had previously attached the mine to surface ownership. The first ore-dressing plants were installed by German engineers upon the classic models of the Harz and of Freiberg; but in 1880 Sardinia commenced to open a new path in that industry, utilizing the refuse from the mining of rich, selected minerals, of poor deposits, and of mixed ores. The first experiments were attempte to adapt the existing apparatus to local conditions, but progress was rapid, as was demonstrated already in 1887 by the calamine-dressing mill of Monte-poni, which exhibited a large plant designed in accordance with the experience gained, and constructed entirely in the machine-shops of the country, after new models and designs.' This example was followed two years later by the Sociékté Malfidano, with a large plant of the same sort, and with the reconstruction of the old-fashioned dressing-mill, built in 1880 by the Austro-Belgian Company. In 1900, almost all the mines of Sardinia had adopted the new designs, and the island contained 32 concen-trating-works, employing 2,000 h.p. and 1,924 workmen. Since that time, there have been added a large dressing-mill for blende at Gennamari, and two for calamine, at San Giovanni and at Masua, while the establishments at other mines have been enlarged and perfected. For the treatment of intimately mixed ores, a large establishment has been built upon the new

Jan 1, 1909

TO THE BOARD OF DIRECTORS AND MEMBERS Of THE AMERICAN INSTITUTE OF MINING AND METALLURGICAL ENGINEERS GENTLEMEN Submitted herewith are the reports of the Treasurer for the year 1947 and the reports of the following standing committees Membership, Admissions, Papers and Publications, MINING AND METALLURGY (Magazine), and Library 75th Anniversary Celebration The founding of the Institute at Wilkes-Barre, Pa, in 1871, vas appropriately commemorated by a three-day Celebration, March 17, 18 and 19, 1947, at The Waldorf-Astoria, in New York City The Celebration had been scheduled for the preceding September but had been postponed, perforce, because of conflict with meetings of the Assembly of the United Nations The Celebration immediately preceded the Annual Meeting which was deferred from the usual February dates The proceedings took the form of a "World Conference on Mineral Resources " More than three thousand people, including eight hundred ladies, participated in the proceedings in one way or another Twenty-eight foreign countries were represented, some of them by five or six individual delegates Likewise, official representatives were designated by fifty institutions of higher learning in the United States A special 820-page Anniversary Volume entitled "Seventy-five Years. of Progress in the Mineral Industry,".(which

Jan 1, 1952

TWO American students entered the École des Mines in 1856, Joseph Lesley of Philadelphia and Thomas Egleston of New York. Lesley remained there only one year, but Egleston completed the whole curriculum and received, in 1860, the certificate given to foreign students in lieu of the official appointment and degree awarded French students. Returning home he received, in 1861, an appointment by Secretary Henry of the Smithsonian Institution to sort, label, and arrange the collections of mineralogical and geological specimens which had been brought to Washington by the various government exploring expeditions in the West. Thomas Egleston, born in New York City on Dec. 9, 1832, was the son of Thomas Jefferson Egleston, who came to New York from Massachusetts some time before 1829. The first American ancestor of the family had settled near Dorchester in 1630. T. J. Egleston and Joseph Battell established an iron-merchandizing business* at 166 South St., New York, which prospered exceedingly; so much so that when Thomas J. Egleston died, July. 12, 1861, his estate had a book value of over $500,000. Since an older brother was expected eventually to take over this business, Thomas, who had a liking for science, went to Yale, where he completed the regular four-year course in 1854, and then remained another year for advanced work in chemistry under Silliman. One biographer says he went to Europe, early in 1856, on account of his health. It was the custom at that time for wealthy young men to make a tour of Europe after completing their academic education. Whatever the precise reason, he began scientific work at the Jardin des Plantes in Paris but soon trans-

Jan 1, 1941

GENTLEMEN Submitted herewith are the report of the Treasurer for the year 1938 and reports for the same year of the following standing committees: Admissions, Membership, Papers and Publications, Mining and Metal¬lurgy (Magazine), Library, Speakers for Local Sections and Student Societies, and Student Relations. To these reports members are referred for further details. Membership.-The end of the year 1938 saw Institute membership at an all-time peak: 12,474, made up of 2898 Student Associates and 9576 members of other classifications. The next highest level had been reached at the end of 1921 when corresponding figures were: total, 10,329; student members, 1450; all other classifications, 8879. The net gain for the year was 1495, of which 751 were Student Associates and 744 in the other categories. Two factors contribute to the growth of membership: (1) the enrolment of new members; and (2) the retention of members already on the roll as reflected in a relatively small number of resignations and suspensions for nonpayment of dues. For the first, much credit goes properly to the general Membership Committee that functioned for a second year under the chairmanship of Clyde E. Williams. With the cooperation of Institute members in general, to whom Mr. Williams expresses appreciation in his report, the Committee has been successful in acquainting eligible nonmembers with the purposes, activities and advantages of the Institute. The result has been the receipt during the year of 1162 applications, exclusive of Student Associates. This compares with 1212 during 1937 and 1266 during 1936. However, in considering this modest decline, account must be taken of the somewhat less prosperous conditions prevailing in the mineral industries and, consequently, among engineers engaged ?in those industries.

Jan 1, 1939

By Frank Hall

THE needs of the World War showed the necessity of a metal stronger than cast iron which would supplement the supply of steel. So patriotic metallurgists were spurred to new efforts to improve the status of that half-breed of the metal world that had been, more or less erroneously, christened semisteel. As a result, it was developed that for certain purposes semisteel was superior to steel in the manufacture of shells. Steel, because of its greater strength and toughness, is able to carry a greater charge of explosive, weight for weight; consequently, a steel shell can be expected to cause greater destruction when used against fortifications or other inanimate objects, while semisteel, because of its comparative brittleness and its resulting greater fragmentation, is capable of inflicting more serious loss of life when used against opposing forces of men. Therefore, each has its proper place in the economy of war. For the present purpose, steel may be defined as a comparatively pure iron whose physical nature is modified by small amounts of carbon, silicon, sulfur, phosphorus, manganese, and possibly other rarer elements; while cast iron generally is limited to approximately 93 per cent. of iron, the remainder consisting of larger percentages of carbon, silicon, sulfur, phosphorus, and manganese. Semisteel may be defined as cast iron in which the carbon and silicon have been reduced to as low a point as is consistent with maintaining the nature of gray iron, and in which the remaining elements are manipulated so as to give the greatest strength.

Jan 1, 1920

By E. W. Filer, R. P. Smith, L. S. Darken

The solubility of nitrogen gas in purified iron and low alloy steels is determined for the y region (930° to 1350°C). The diffusivtiy of nitrogen is estimated from the rate of approach to equilibrium. The investigation of aluminum-killed steels, held in nitrogen, discloses precipitation of aluminum nitride, the solubility of which is determined. ALTHOUGH several investigations of the solu-bility of nitrogen gas in y iron have been reported, all have made use of the method adopted by Sieverts in his classic work, whereby the solubility is determined by the pressure or volume change of the gas. The agreement between different investigators* is rather poor, particularly as compared to the self-consistency of results of several individual investigators. The present report represents a portion of our investigation of the equilibrium of nitrogen and nitrogenous atmospheres with iron and steels. The method adopted in this temperature region (910" to 1400°C) consists of holding the specimen in gaseous nitrogen, quenching (or cooling), and determining the nitrogen content by direct analysis (solution in acid followed by distillation and titra-tion of the ammonia).** Up to 1050°C a 20 in. vertical wire-wound (Kan-thal) furnace was used; this was wound in three sections so that by proper adjustment of relative currents, and use of a modulator1 and a commercial controller (using a chromel-alumel control couple), a zone almost 6 in. long could be maintained uniform within a few tenths of a degree. Since the temperature coefficient of the nitrogen solubility is low, the full precision was not utilized and a variation of l° to 2" was tolerated; a variation of a similar amount also occurred occasionally between the beginning and end of the experiment. At higher temperature a vertically mounted, tubular Globar furnace and control unit was used; the zone of uniformity (l° to 2"C) was here limited to about 2 in.; fluctuations with time were comparable to those in the wire-wound furnace. Reported temperatures were measured by use of a platinum-platinum-rhodium thermocouple, which was frequently com- pared with a similar standard couple which was calibrated at the gold and palladium points and also compared with one certified by the Bureau of Standards; error from this source is believed to be less than 1 "C. Nitrogen gas from a commercial cylinder was mixed with slightly over 1 pct H by use of a gas mixer described previously.' This mixture was passed over hot copper and through ascarite and phosphorus pentoxide to remove oxygen and water vapor. The purified gas contained 1.05 pct H. This procedure was adopted to prevent the formation on the specimens of oxide film, which is well known to be nearly impervious to nitrogen; its success was attested by

Jan 1, 1952

T. T. READ, Secretary of the Committee on Industrial Organization, presents the following very interesting monthly ad interim report: Reports from London are to the effect that 750 housing schemes for workers, involving the erection of 128,000 new dwellings, have been submitted to the Local Government Board. Birmingham alone needs 14,000 new houses, and the Housing and Town Planning Committee of the City Council considers that 5000 new houses must be built each year for the next 20 years. Nine hundred acres of land has been acquired, on which to build 10 to 12 houses per acre for the next two years. The town of Dudley, which built 300 modern dwellings in 1915-1916, submitted schemes for another 500 houses. There is a shortage of building materials required, specially brick. Financial assistance has been received for reopening brick yards that were closed during the war. W. E. Dickson, vice president of the Midvale Steel & Ordnance Co., is reported in the daily press as stating that his corporation is planning to spend $8,000,000 in improving its plant and assisting its employees in building their own homes. The company will advance 90 per cent. of the cost of the house and extend payments over a period of 12 years. Methods of work employed in building 256 houses at Quincy, Mass., for the workers of the Fore River shipyards are described, by Joseph Meltzer, in the Engineering News Record for May 29, 1919. The approximate cost was about $3500 per house, not including water supply, sewers, streets, and sidewalks. "Comparative Costs of Tenantry and Home-Owning;" "A Plain Talk on Helping Home-builders;" and "More Plain Talk on Home Building" are the titles of three publications of the Information and Education Service of the Department of Labor. These publications should be' of a good deal of service in convincing employees that it is to their interest to own their homes rather than to live in rented houses. The same Service has issued pamphlets discussing the cost of materials.

Jan 7, 1919

By James A. Barr

[CONTENTS PAGE Foreword. By JAMES A. BARRI A New Core Barrel for Prospecting for Phosphate in Florida. By I. M. LEBARON 2 Prospecting for Phosphate in Tennessee. By W. F. GUENTHER 6 Machine Prospecting in Tennessee Brown Phosphate. By H. O. PICKARD, JR8 Diamond Drilling through Flint Horizons in Tennessee. By HENDON R. JOHNSTON9] Foreword PROSPECTING methods used in Tennessee have gradually improved with the years, as required by depletion of the easily accessible and shallow deposits and the universal trend toward mechanization, and as necessitated by exploring deeper beds, often occurring under limestone and flinty overburden. In the early days it was a very simple matter to dig pits by hand, using a plentiful supply of local farm labor to expose relatively shallow deposits of "brown rock" under shallow clayey overburden that would stand up without timbering. Visual inspection of the exposed phosphate and expert judgment of the"grade" analysis, aided by a "biting" test to reveal presence of unwanted silica, furnished most of the information required. All this might be helped by a few samples sent to the local chemist[t] who supplemented his income by judicious trading or tanning a few bear skins. The extra curricula activities did not affect the accuracy of the analysis which hold up even under present day standards. Some shot and core drilling was done in Hickman County, mostly for the limestone-like blue Phosphate deposits. The next step was the use of a 4-in. posthole auger, hand operated as described by Guenther, followed by- a completely mechanized rig, as described by Pickard. Both these methods are practically adapted to the prospecting of the relatively soft brown rock deposits at moderate depths of clay overburden. For prospecting in areas of deeper overburden, such as are often found in Hickman County, up to 150 or even 200-ft depths, a modified core-drilling method is described by Guenther. Johnston describes a special diamond-drilling technique, developed by TVA, to penetrate flint horizons, which was adopted by the International Minerals and Chemical Corporation to prospect in Hickman County where deposits had previously been prospected at considerable expense and with difficulty, by Small, temporary, hand-dug shafts.

Jan 1, 1947

OFFICIAL INSTITUTE REPORTS FOR THE YEAR 1924 Report of the Secretary TO THE BOARD OF DIRECTORS OF THE AMERICAN INSTITUTE OF MINING AND METALLURGICAL ENGINEERS Gentlemen -To a Board of Directors keeping in as close touch with all of the affairs under their care as do the Directors of the A -I M. E, through their monthly meetings, a report of the year's progress is almost superfluous To the members who read the monthly reports of the Board Meetings and of the various activities of the Institute as published each month, a yearly report cannot carry much fresh infor¬mation, yet for both it may be well, as is the custom, to glance over the field of our activities during the past year, and to make an estimate for the year to come The beginning of 1924 was not propitious for the members of the mining profession, though tonnage, production for 1923 had been high and the gross value higher than for several years The margin of profit had been narrow, prospecting and development were limited, and many of our members were unemployed or were working in other industries Toward the end of the year, higher metal prices were in sight Old-time optimism began to grow, and it now brightens the outlook for 1925 An excellent barometer of the prosperity of the industry, and that of the Institute, for they go hand in hand, is the work of our Employment Bureau During the past few months, the percentage of our members for whom openings have been found has been increasing to a marked extent, and many members who had fallen in arrears are placing themselves in good standing The number of new members joining has remained about as it was in 1922 and 1923 The Directors have reason to congratulate themselves on the interest maintained during a dull period, for it is not humanly possible to take a keen interest in the technology of an industry when our hands and minds are not actively engaged in it Now, with a much brighter outlook, we can look forward to a year of increasing prosperity for the industry and for the Institute

Jan 1, 1923

By Leonard H. Goldman, Harold E. Marr

The PGT uranium assay probe is a borehole tool developed by Princeton Gamma-Tech over the last several years. It has the ability to do an in-situ assay of uranium in the presence of any amount of disequilibrium. It has some advantages over coring including cost, speed of analysis, and accuracy. In this paper we would like to give a brief description of the measurement and then show some sample logs from South Texas. Uranium exploration and development is carried out primarily by gamma logging since uranium daughters are prolific emitters of gamma rays. The conventional gross gamma tool for uranium logging is limited in value because of the inability of this tool to distinguish uranium from its daughters and other naturally occurring radioisotopes, such as potassium and thorium. This problem becomes severe in cases of disequilibrium. Disequilibrium, in a geological context, is defined as the condition when the gamma radiations from the daughter products are being emitted in a location different from that of the parent uranium. In the decay chain of uranium almost all the gamma radiation emitted in the entire chain comes from the daughter product, bismuth-214. Bismuth-214 is separated from uranium by several long-lived isotopes that are chemically active and have different physical properties, often resulting in shifts in the location of bismuth- 214 relative to the parent uranium. In the United States orebodies exhibiting disequilibrium are a common occurrence and the use of a gross gamma log to delineate uranium orebodies can lead to errors. At present the solution to the disequilibrium problem is extensive coring followed by chemical analyses of the cores. There are several drawbacks in using this technique. First is the high cost of coring, the second is the fact that no results are available for days, or typically, weeks after the drilling is done. Thus for development work, coring and drilling must be done on a grid basis and many additional holes are cored to ensure that the entire orebody is mapped. Another disadvantage to cores is the fact that a small volume is sampled, the volume of the core itself. This leads to problems in the mapping out of the orebody when the ore de- posit is not very homogeneous. The PGT probe described in this paper is a new solution to the disequilibrium problem. Basically, the probe measures radiations that come almost directly from uranium itself. The first daughter of uranium, which is protactinium-234 (Pa-234), is only separated from uranium by a 24-day half-life and no disequilibrium problems build up in such a short time. The PGT probe measures the intensity of a one MeV gamma line emitted by Pa-234 and, using this information, calculates the concentration of uranium. The PGT probe is 24" in diameter and 12 feet long. The probe contains a microprocessor which passes the information to a larger minicomputer in the truck. All data is analyzed on site, and the results from a high speed printer are presented to the geologist. Data is also available on 9- track IBM compatible tape for further processing. The PGT probe output is linear with uranium concentration. The only correction factor is for borehole size, and that only becomes important in boreholes bigger than seven inches in diameter. Dead time is compensated in the probe itself and no problems have been encountered in ore zones up to several percent UjO8. In addition to the uranium assay, a conventional gross gamma log is plotted alongside. Grade thicknesses for zones above cutoff are calculated as well as disequilibrium factors. COMPARISONS During its commercial operation PGT logged a series of 18 holes that had been cored and assayed. All of the holes in this series were logged in normal operation by regular field operators. The time to log each hole was generally under an hour, and in typical operation a PGT logging truck will do between 7 and 8 holes a day. The results of the comparison of the PGT and the core assays are presented in a series of figures showing plots of the PGT assay, core analysis and gross gamma measurements. The first three figures show individual holes with the gross gamma plotted along with the core and the PGT assays. All three logs were from holes on the reduced side of a rollfront deposit in South Texas. In Figure 1 we see the two wings of the roll- front at 143 ft and 150 ft separated by a barren zone. The wings are well defined both by the PGT assay and the core. There is approximately a one foot shift which can be attributed to drilling errors. The gross gamma is showing a rather severe discrepancy, being considerably lower and not showing the barren zone. The grade thickness calcula-

Jan 1, 1980

By G. H. F. Gardner

The boundary conditions F = 1.0 and 4 = 1.0 (100 per cent) are dictated by the definition of F in the equation 1/F = aFp. These conditions have physical significance as the "limiting conditions" for the observed behavior in systems of dispersed particles. The other boundary conditions, cited by Gardner in his Eq. 3 as applying to this system, have no significance in the systems we studied. Maxwell's equation (Eq. 2) cited in Gardner's comments was developed for and limited to a regular, rather than random, dispersion of spheres which are sufficiently removed from each other so that they do not interfere with current flow about their neighbors. These restrictions also apply to Rayleigh's analysis. The title of Rayleigh's paper cited by Gardner is "On the Influence of Obstacles Arrayed in Rectangular Order upon the Properties of a Medium". He is not discussing randomly dispersed spheres. It might be inferred from Gardner's comments that Rayleigh specifically considered the differential equation (Gardner's Eq. 3). This is not the case. Mathematically, Gardner's Eq. 3 is exactly true for the system to which it applies, however, as both Rayleigh and Maxwell note that their equation for F in terms of F is not for randomly dispersed spheres. At the time we wrote our paper, we were aware of the work of Wyllie and Gregory as cited by Gardner. We cited their work in Ref. 5 of our paper. Our comment on page 287 of the paper about the validity of an m value of 1.3 for spheres with a porosity of 38 per cent remains as our answer to Gardner's question on this point. Our data, at 38 per cent porosity, show that the condition a = 1 and m = 1.3 holds for spheres near 40 per cent porosity.