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By Steven J. Page, John A. Organiscak

Airborne dust generation is one of the byproducts of coal mining, processing, and handling. The amount of airborne total dust (ATD, respirable size and larger) and airborne respirable dust (ARD) generated is of primary interest for designing the level of engineering controls needed for adequate dust abatement. Laboratory crushing experiments were conducted in a wind tunnel with a roll crusher to identify relationships among crushing parameters, product size, coal rank properties, and airborne dust generation. Through the first series of experiments, the effect of primary and secondary breakage processes on both product size and airborne dust generation was examined. Through a second series of experiments, the effect of coal rank properties on product size and airborne dust generation was studied using a uniform crushing process with secondary breakage. Laboratory results indicate that secondary breakage of a particular coal notably increases the specific amount of ATD generated, while negligibly impacting the specific amount of ARD generated. A strong positive relationship was identified between the specific amounts of ATD and ARD generated during the primary breakage process (with minimal secondary breakage), but a negligible relationship was observed between the same two variables when secondary breakage was introduced into the crushing process. This indicates that most of the ATD and ARD is generated from the primary breakage, while secondary breakage has a more of an influence on generating additional amounts of larger sized ATD. Additional experiments involving the uniform crushing of eight different bituminous coals showed that the coal rank, expressed as the inherent moist fuel ratio (MFR = fixed carbon =(volatile x inherent moisture)), had diverse relationships between the product size created and the amount of airborne dust generated. As bituminous coal rank or MFR increased, the amount of coal product fines < 250 gm increased while the mass percentage of ATD and ARD liberated from these < 250 µm product fines decreased. Air dry loss (ADL) moisture in the coal was found to be inversely related to the dust cloud electrostatic field, influencing dust liberation from the coal product fines. Since the MFR was directly related to the dust cloud electrostatic field, opposite the ADL-electrostatic field relationship, the diverse relationships between the product size created and the amount of dust liberated from the < 250 µm product fines were explained. Finally, 12 to 14 times more ATD was generated as compared to the ARD generated during these experiments. These results should provide a fundamental basis for initial estimation of the airborne dust loading requirements of engineering control methods for coal crushing.

By Antonio Huerta

The effects of potassium ethyl xanthate collector and potassium dichromate used as a depressor on a PbS mineral were studied by high frequency impedance technique. Measurements of complex permittivity, at 100 MHz suggested that is possible to obtain from isotherm adsorption the adequate industrial collector concentration being this in the range of lE-3 to 5E-3M of KEX. The e&apos; values (320-420) in the PbS-KEX system was increased as the KEX concentration was lowered). In the other hand the PbS- K2Cr2O7 system showed higher values of e&apos; (420-510) as the K2Cr2O7 concentration was increased. The PbS-KEX-K2Cr2O7 system was evaluated.

Jan 1, 1997

By Mary H. Brown

The heats of formation of oxalic acid and sodium, potassium oxalates, and lithium oxalates were related by solution calorimetry to the heat of formation of (COOH)2.2H20, a value believed to be reliable as reported in the literature. The following heats of formation were determined: (COOH)2(a), -198.1±0.1; (COOH)2(ß), -197.8±0.1; UAW,, -328.7±0.4; Na2C204 -316.2±0.1; K2C204, -321.9±0.2; and K2C204-H20, -393.5±0.2 kcal/mole. The heat of the crystalline transformation (COOH)2(a) ? (COOH)2(ß) was determined to be 0.30±0.02 kcal/mole at 298.15° K.

Jan 1, 1970

By P. G. Coombs

The kinetics of the cyclic oxidation and reduction processes for palladium powder were examined in the temperature range 848 to 923 K. The changes in oxidation behavior due to cycling are shown to result from the decrease in surface area. Sintering is found to occur only during the reduction process. Oxidation kinetics were found to follow a cubic law with time and yield a relation for the oxidation rate constant of k x = (1.05) 106 exp P74.0). 103 / RT] The kinetics of reduction are demonstrated to be first-order with the rate constant described by the expression: kr = (7.69) 1012 exp [-(208.0) 103 / RT] . In both expressions R is in J.mo1-1.K-1.

Jan 1, 1984

By Takao Mori

Novel rare earth boron icosahedral compounds are investigated as potential high temperature thermoelectric materials. REB50-type compounds and REB22C2N compounds were synthesized and the thermoelectric properties measured. Seebeck coefficients in excess of 200 V/K are observed at temperatures above 1000 K for the REB50-type compounds. Strikingly, n-type behavior was observed for REB22C2N. Up to now, non-doped B12 icosahedral compounds have all been p-type. The discovery of an n-type compound is extremely important in terms of the potential development of this class of compounds as viable thermoelectric materials. Low thermal conductivities of < 0.03 W/cm/K at room temperature was observed for these rare earth boron cluster compounds.

Jan 1, 2006

By Jim Breedlove, Stephen P. Case, Mike Fabio

To meet salt production needs over the remaining life of the Cayuga Mine at Lansing, New York, the Salt Division of Cargill, Inc. decided to build a new underground screening plant. The new plant required a chamber 50 feet wide by 250 feet long and nearly 70 feet high. On advice of their mining contractor, Dynatec Mining Company, the company chose an ingenious excavation method similar to sublevel stoping. This method eliminated the need for an access ramp, reduced equipment needs and excavation time substantially.

Jan 1, 1996

By Callaghan T

The Henty Gold Mine is located approximately 30 km north of Queenstown, at the head waters of the Henty River on the west coast of Tasmania at 41¦50&apos;S, 145¦40&apos;E on the Queenstown (SK 55-5) 1:250 000 and Sophia (8014) 1:100 000 map sheets (Figure 1). The mine is accessed from Queenstown along the A10 Highway and Anthony&apos;s Road. The town of Queenstown is located 260 km north west of Hobart on the A10 Highway, and

Jan 1, 1997

Potential hlghwaJl mining reserves in Australia are large, but geotechnical and operating conditions are quite different from those where highwall mining has evolved in the USA. In order to achieve safe and effective resource recovery, equipment and procedures should be developed to penetrate 250 m in the Australian mining environment. This paper identifies key auributes to be incorporated in such machinery and methodology. These suggestions are intended to promote discussion on innovations to satisfy Australian requirements for highly productive, safe and environmentally acceptable techniques.

Jan 1, 1993

By Raymond W. Hiteshue, Sam Friedman, Robert Madden

Experiments were made in a semicontinuous unit to provide engineering data for designing experimental continuous systems . These systems would be used to study the hydrogasification of hvab coal and char (from lowtemperature carbonization ) to high - Btu gas . In experiments at 800 ° C and with a coal residence time of several seconds , yields of hydrocarbon gases increased from about 2,000 scf / ton of maf coal at 250 psig to 7,000 scf at 1,000 psig . With 15 minutes residence time , yields increased from 8,000 scf/ton of maf coal at 250 psig to 17,500 cubic feet at 1,000 psig . In all cases , small quantities of heavy oils were produced along with the gaseous hydrocarbons . Production of oils could be minimized with a corresponding increase in gaseous hydrocarbons by increasing the retention time of the volatiles within the hot zone . Yields of gaseous hydrocarbons from char were slightly greater than from coal under similar conditions . Although the hydrogasification reaction is very pressure dependent , substantial quantities of coal (40 to 60 percent ) could be reacted to gaseous hydrocarbons at pressures as low as 50 psig provided reaction temperatures were increased to 1,200 ° C. It was also demonstrated that a hvab coal could be hydrogasified continuously without incurring agglomeration . This was achieved by dispersing coal in a relatively large reactor with concurrent flow of hydrogen . At 1,000 psig and 800 ° C , it was possible to react about 35 percent of the coal and to produce a gas containing up to 52 percent methane .

Jan 1, 1964

By Leiliane Alves de Oliveira

O aço EUROFER (9Cr – 1W), pode ser utilizado em turbinas para geração de energia, vasos de pressão, reatores nuclear ou aplicações, onde o material é submetido a temperaturas de serviço entre 250°C e 450°C. Uma forma de melhorar as propriedades do aço, para que ele trabalhe a temperaturas mais altas ou que se torne mais estável é adicionar partículas de segunda fase na sua matriz. Estas partículas podem estar na forma de óxidos, carbetos, nitretos ou até mesmo em solução sólida quando alguns elementos químicos são adicionados ao material. Neste contexto, este trabalho objetiva estudar o efeito da adição de 3% de carbeto de tântalo na matriz metálica do aço ferrítico/martensítico. Para isto a metalurgia do pó foi a rota empregada para a produção deste compósito de matriz metálica (CMM). Duas moagens distintas foram realizadas. A primeira com o aço EUROFER e a segunda com o aço EUROFER com adição de 3% de carbeto de tântalo (TaC). A moagem de alta energia foi realizada durante 5 horas. Em seguida, os dois pós produzidos foram sinterizados em um forno a vácuo (10-4torr) a temperatura de 1.250°C durante 60 minutos. O produto final foi caracterizado por microscopia óptica, microscopia eletrônica de varredura (EDS) e ensaio de microdureza. Os estudos iniciais dos sinterizados obteve uma resposta positiva nas propriedades mecânicas independente do processamento. Com valores de microdureza maior que 100% do valor de 333,2 HV obtidos para o aço puro como recebido(barra).

Aug 8, 2018

By F. S. Hoseinian, M. Irannajad, M. Safari

In this study, the effect of chemical interactions of materials used in ion flotation on the removal of Ni(II) ions from low concentration synthetic wastewater was studied. Sodium dodecyl sulfate (SDS) and ethylhexadecyldimethylammonium bromide (EHDABr) as collectors and methyl isobutyl carbonyl (MIBC) and Dowfroth250 as frothers were used. To investigate the effective parameters and interactions of them, 16 experiments including 6 level variables were performed by supporting DX7 software and on the bases of 2-level factorial method. In the first step, the tests were conducted in a Hallimond tube. The result showed that collector of SDS and frother of Dowfroth 250 had appropriate interaction with each other at pH = 3. In the second step, optimal results from the first step were evaluated in a mechanical flotation cell. The removal of Ni(II) ions increased by increasing the time of flotation and they have a direct relation with the water removal. The kinetics study shows that the order and the rate of removal of the reaction do not follow any of the zero-order, first-order and second-order equations. The flotation rate curve on the removal of Ni(II) ions will divide the separation process to two stages, a fast flotation rate at the first stage and a slow flotation rate at the second stage. Ni(II) ions removal was obtained 88% at the best condition.This study showed that the use of ion flotation was a very effective method for Ni(II) ion removal from industrial wastewaters.

Jan 1, 2016

By A. M. Glendinning

"IntroductionLocationTHE PROPERTY of Aunor Gold Mines, Limited is in Deloro township, Ontario, about three miles southeast of the town of Timmins. It consists of a group of eleven claims located between those of Buffalo-Ankerite Gold Mines, Limited, and Delnite Gold Mines, Limited.GeologyThe ore zone at the Aunor mine consists of a narrow band of fine grained pillowed andesite, irregular bands of 'brown to green carbonated andesite, and lenticular bodies of quartz feldspar porphyry. The zone strikes N.80°E., dips 60 North, and has been traced for 5,000 feet across the property. It varies in width from 0 to 250 feet and is bounded on the north and south by masses of dark bluish-grey tale chlorite schist. These schist bands have widths up to 500 feet.The ore occurs in a series of parallel and branching veins confined to the limits of the zone. These veins tend to terminate and die out on the footwall schist contact, striking generally parallel with the ore zone. In wide sections of the zone, 150 to 250 feet, the veins range in width up •to 3.5 feet and may occur in two or three horizons across the width of the zone, each mineable independent of the other. They tend to dip a little flatter than the general dip of the zone. Where the zone is narrow, the veins are so closely spaced and numerous they can be mined together and in some places the complete zone has been mined from schist to schist."

Jan 1, 1953

By S P, F Villanueva, R Palomo, D Meadows

During 2002, design and development of the worldÆs largest flotation cell was completed. The cell is the mineral industryÆs first 257 m3 flotation cell, and represents a major development in the design of larger flotation cells, with a 50 per cent increase in cell volume over the widely installed 160 m3 WEMCO« SmartCellTM flotation machine. It is anticipated, in the next few years, world-class copper sulfide concentrators will incorporate 257 m3 flotation cells in their rougher-scavenger flotation circuits. The prototype 257 m3 cell, No 250 SmartCellTM flotation machine is installed in Minera Los PelambresÆ existing rougher flotation circuit. The machine is located in front of the first cell in Row 1 and is followed by nine No 130 SmartCellTM flotation cells. The unit has been in operation since April 2004, and has proven itself in this duty. A key to the successful development of the equipment has been the emphasis placed on fundamental hydrodynamic scale-up criteria. Hydrodynamic factors include superficial gas velocity, water (pulp) circulation through the draft tube, and pulp mixing (distribution) characteristics. This paper will review the scale-up criteria of the No 250 flotation cell, and a case study will be presented on the in-plant testing of the equipment. The case study will document the metallurgical and hydrodynamic performance of the machine. It will also illustrate the economic benefits derived by incorporating larger flotation cells in a modern copper sulfide concentrator.

Jan 1, 2005

By Steven P. Case

To meet salt production needs over the remaining life of the Cayuga Mine at Lansing, New York, the Salt Division of Cargill, Inc. decided to build a new underground screening plant. The new plant required a chamber 50 feet wide by 250 feet long and nearly 70 feet high. On advise of their mining contractor, Dynatec Mining Company, the company chose an ingenious excavation method similar to sublevel stoping. This method eliminated the need for an access ramp, reduced equipment needs and excavation time substantially.

Jan 1, 1996

By Ray W. Carpenter, Ralph Hultgren, Raymond L. Orr

Heats of formation of Au-Zn alloys of compositions Au3Zn and AuZn were rneasured at several temperatures by liquid tin solution calorimetry. The data for Au3Zn show that much smaller heat and entropy effects are associated with the a2- a1 transformation than for the a1 - a transformation. This result is consistent with reported X-ray diffraction studies which indicate that the a1 and (a2 phases have ordered structures which only slightly differ, whereas the a phase is disordered. The heat of formation of AuZn(ß&apos;) does not change significantly between 322o and 8000 K, confirming that the ß&apos; alloy remains highly ordered to high temperatures. Not many measurements have been made of the energies of order-disorder transformations in alloy phases. In many cases these energies may be conveniently determined by measuring heats of formation as a function of temperature. Many alloy phases approximately obey Kopp&apos;s law of additivity of heat capacities; as a consequence their heats of formation do not change with temperature. In ordered alloys, however, a decrease in degree of order with increasing temperature will contribute an endothermic component to the heat of formation. Thus, for ordered phases where other anomalous contributions to heat capacity in the alloy or its pure components are absent, a measured change in the heat of formation may be attributed to the energy of disordering. A portion of the Au-Zn phase diagram1" is shown in Fig. 1. The composition AuZn(ß&apos;) has a well-ordered superlattice structure of the CsCl type at room temperature. The alloy is considered to remain ordered to its melting point,1 although, from X-ray diffraction data and electromotive force measurements of zinc activities, Terpilowski3 concluded that considerable disordering began at -673°K. The Au3Zn composition is a disordered fee solid solution (a) at high temperatures. Between 693o and 543oK, the ailoy orders to form the a1 phase, having a structure based on the L12(AuCu3) type, but with a regular distribution of ordering faults in the c direction, making it tetragonal. Below 543oK, the alloy orders further by means of slight atomic shifts, without diffusion, yielding a complex long-period orthorhom-bic superlattice structure, a2.4-7 Heats of formation of Au3Zn(a2) and AuZn(ß&apos;) were measured at 363°K by Biltz et al.8 by aqueous solution calorimetry. Heat capacities of several alloys between 14.9 and 38.4 at. pet Zn in the range from 373" to 723°K were measured by Iwasaki ef al.6 Stoichiometric Au3Zn, however, was not included in the alloys measured, the nearest composition being 26.1 at, pet Zn. Also, the heating rate used for the measurements, 2 deg per min, may not have permitted equilibrium to be reached in the neighborhood of the transformations. Heat contents of solid and liquid AuZn were measured between 488o and 1138°K by Kubaschewski.9 It was decided to determine the ordering energies of Au3Zn and to check on the possible disordering of AuZn by measuring the heats of formation of these alloys at several temperatures. The present paper reports measurements by liquid tin solution calorimetry of the heats of formation of the three phases of Au3Zn at temperatures within their regions of stability, and of AuZn at a low (322°K) and a high (800°K) temperature. EXPERIMENTAL Alloy Preparation and X-Ray Examination. Ten-gram ingots of Au3Zn and AuZn were prepared by melting weighed amounts of gold (99.95 pct Au) and zinc (99.99 pet Zn) together in sealed evacuated Vycor tubes at 1060°K, followed by rapid quenching. The resulting ingots were homogenized at 900°K for 10 days. The Au3Zn alloy lost no weight in preparation, the loss from the AuZn alloy was enough to introduce an uncertainty of only 0.1 at. pet in its composition. Filings for X-ray examination were taken from various parts of each ingot and strain-annealed at 723°K for 20 min in vacuo. The Au3Zn filings were quenched rapidly to retain the disordered phase. Diffraction patterns were determined with an X-ray dif-fractometer using copper Ka radiation.

Jan 1, 1968

By Robert E. Wood

The temperature dependency of the low-density viscosity coefficients, ?°T, of helium and of nitrogen, 100° to 1,000° K, is correlated with empirical equations, and the temperature and composition dependencies of the low-density viscosity coefficients, ?°T, of helium-nitrogen mixtures are correlated with the Chapman-Enskog expressions by using the Lennard-Jones (6:12) potential function. The residual viscosity, ?T,P - ?°T (the difference between the viscosity of a compressed gas and the dilute gas at a given temperature), was found to be a function of the thermal pressure coefficient, (?P/?T)V, and two parameters, a and 1, which are characteristic of gas composition. The equation ?T, P = ?°T + a [(?P/?T)V]ß represented 1,340 higher pressure experimental viscosity values with a mean absolute deviation of 0.86 percent, and this equation was used to compute viscosities of the gaseous helium-nitrogen system for a range of temperatures and pressures including those encountered in Bureau of Mines helium purification processes and in a crude-helium conservation gas reservoir. Tabular viscosities for helium, nitrogen, and 13 helium-nitrogen mixtures are presented for 110 temperatures, 133° to 740&apos; K, and 49 pressures in the range 1 to 240 atmospheres. The accuracy of the tabulated viscosities varies because correlation parameters were obtained from experimental data of unequal reliability. It is estimated that uncertainties in the computed viscosity values are ±5 percent for the region 325° to 740° K, ±2 percent for the region 183° to 325° K, and ±5 percent for temperatures below 183° K. The latter uncertainty may rise to y10 percent as critical conditions are approached.

Jan 1, 1970

By F. R. Brotzen, L. D. Whitmire

Single crystals of high-purity molybdenum were de-formed at temperatures from 195°to 473°K, and the effect of deformation on the electrical resistivily was deler-mined. To separale the resislivity components of point and line defecls some cryslals were annealed at 473°K. The vale of resislivily increase wilh strain was nearly linear and was strongly dependent upon the deformation temperature. Point dejects are annealed out without any effect on the flow stress. At low temperatures the flow stress is a linear function of the square root of the resistivity increase attributable to dislocations. ELECTRICAL-resistivity measurements have been used successfully to gain information on structural changes in metallic materials. During plastic deformation the electrical resistivity rises because of electron scattering from newly created lattice defects. Such measurements lend themselves, therefore, to corroborating results from direct observation of lattice defects and, to a certain extent, to correlating defect densities and distribution with mechanical properties. Published information on research with single crystals of the bcc metals of Group VI, particularly molybdenum, is still limited. Yet, molybdenum single crystals of relatively high purity can be readily prepared by electron-beam-melting techniques. Furthermore, some valuable information on the defect structure of deformed crystals by direct observation is available. Lawley and Gaigher,1 for example, have examined dislocation configurations in deformed molybdenum crystals by means of transmission electron microscopy. Their results revealed that the dislocation density and distribution were strongly dependent upon the deformation temperature. These findings differed from those by Keh and weissmann,2 who found that the average dislocation density in polycrystalline iron deformed between 138° and 298°K depended only on the degree of strain and not on the deformation temperature. Martin3 and peiffer4 showed that point defects introduced in polycrystalline molybdenum by cold work can be eliminated by annealing at a relatively low tempera-ture. In view of their work it became apparent that resistivity measurements of suitably annealed crystals could disclose changes in their dislocation structure and contribute to the understanding of the work hardening of molybdenum crystals. EXPERIMENTAL PROCEDURE Crystals were grown by electron-beam zone melting5,6 of 0.062-in.-diam molybdenum rods (99.99 pct) supplied by General Electric Lamp and Wire Division, Dover, Ohio. The crystals, about 4 in. long, were prepared by using five zone-refining passes at a speed of about 6 mm per min in a vacuum of about 5 X l0-6 Torr. The resistivity ratio of the crystal, p(4.Z°K)/p(273°K), was generally near 10-3. These crystals were used as tensile specimens of uniform diameter in the "as-grown" condition. They were oriented for maximum shear on the (011)[111] slip system (Schmid factor >0.49). The specimens were held in spherically seated Templin-type grips so as to minimize bending. Samples were deformed on an Instron machine at a strain rate of about 5 X 10-5 sec-1 in an isopentane bath with dry ice at 195°K, in ice water at 273°K, and in a vegetable-oil thermostat at 373° and 473°K. The temperature in the latter was maintained constant within +2°K. Resistance measurements were carried out with a Kelvin double bridge. The resistance of the potential leads was kept low by using large-diameter wires outside the low-temperature bath. Many of the resistance data were checked by measurements made with an ac bridge. Current and potential leads were spot-welded to the specimens. The distance between the potential leads, about 3 in., was also considered to be the gage length for the strain measurements. Diameter and gage length of the samples were measured optically with an error of less than 2 pct. These measurements were used also to insure that the deformation had been uniform over the gage length of the specimen. Resistivity changes were then determined from the resistance measurements at 4.2°K assuming constancy of volume. In the course of a test, the crystal diameter, gage length, and resistance at 4.2°K were determined first in the initial state and subsequently for various amounts of elongation.

Jan 1, 1968

By Gearge C. Wallick

This paper describes experimental procedures for the calibration of capillary tubes to be employed as comparison standards in gas flow-rate measurements and considers several types of flow which were observed in the calibration of seven capillaries of varying diameter. It is shown that under certain experimental conditions deviations from Poiseuille flow are observed which may not be attributed to turbulence, and that this flow behavior may be described empirically by introducing the classical kinetic energy correction into the Poiseuille equation. INTRODUCTION Techniques have been developed for the measurement of the volume rate of flow of nitrogen through glass capillary tubes as a function both of the differential pressure applied and of the absolute gas pressure. Capillary tubes thus calibrated are frequently used to determine the rate of gas flow through a porous sample in the measurement of slip-corrected permeability. The purpose of this note is to describe the calibration procedure and to discuss some observed deviations from the ideal flow behavior predicted by the Poiseuille equation. EXPERIMENTAL PROCEDURE The volume flow rate of nitrogen as a function of the differential pressure was determined experimentally for a series of seven glass capillary tubes of varying diameter. As is shown in Table 1, the capillary radii in the series ranged from 0.004 cm for K1 to 0.07 cm for K7. The capillary tubes were cut from capillary tubing purchased on special order from several manufacturers and the bore radii were determined by microscopic measurement. The gas volume flow rate was measured for each capillary tube at a series of differential pressures in the range from 0 to 3 cm of mercury and at average absolute pressures of 1.0, 2.5, 4.0, and 6.0 atm. Experimental Procedure for Small Capillaries A schematic diagram of the apparatus used to calibrate the three smallest capillaries, Kl, K2, and K3, is shown in Fig. 1. By means of a standard Ruska Instrument Corp. volumetric pump (equipped with a synchronous motor drive, two stages of gear reduction, and a quick-change lathe gear box), nitrogen was displaced by mercury from a metal cell immersed in a constant-temperature bath. The pump, the line to the cell, and a part of the cell were filled with mercury. As mercury was forced into the cell, it displaced nitrogen which passed through the capillary tube being calibrated and into a large container with a volume of approximately 30 liters. Since the volume of this container was very large compared to the total volume change of the gas resulting from the action of the displacement pump, the absolute pressure of the system was essentially constant throughout any one run. Prior to any determination this pressure could be set at any desired level by means of an auxiliary nitrogen cylinder. The differential pressure across the capillary was measured with a Meriam Red Oil manometer and recorded together with the corresponding pump displacement rate which was equal to the gas flow rate. By repeating this process for a series of different displacement rates at each of the absolute pressures of interest, the data necessary for plotting the calibration curves for capillaries K1, K2, and K3 were obtained. All calibration measurements were made in a constant temperature room to minimize errors due to temperature fluctuations. In each run. the flow was maintained until equilibrium was established. Experimental Procedures for Large Capillaries The flow rates through Capillaries K4, K5, K6, and K7 required to obtain the pressure drops desired were larger than could be obtained from available constant displacement pumps, and it was thus necessary to employ an alternative calibration procedure. The arrangement of apparatus used in calibrating these capillaries at an average pressure of one atmosphere is shown in Fig. 2. Each capillary was calibrated by flowing nitrogen through the capillary and recording the differential pressure as a function of the flow rate. &apos;The differential pressure was measured with a Meriam Red Oil manometer and the flow rate was determined by collecting the effluent gas over water at constant pressure and recording the increase in volume per unit time after an equilibrium had been established. Appropriate corrections were made for the

Jan 1, 1953

By Leo Brewer, Kazuyoshi Shimakage, Mamoru Mitomo, Toshiyuki Nishimura, Yoichiro Uemura, Shinji Hirai

"In the synthesis process of ß -La2S3 via the sulfurization of La2O3 powder using CS2 gas, La2O2S was formed. This occurred at an initial stage of the reaction for sulfurization temperatures below 973K, and ß -La2S3 was also formed at a shorter period for higher sulfurization temperatures. It was found that the oxygen content in ß -La2S3 powders decreased gradually with an increase in sulfurization temperature. On the other hand, the carbon content in these powders increased gradually with an increase in the sulfurization temperature. Though it has been reported that ß -La2S3 was transformed to Y -La2S3 at 1723K± 50K, the sintered compact of double-phase Y -La2S3 and ß. -La2S3 was formed at a rather higher temperature of 1973K when the synthetic powder of ß -La2S3 containing a high amount of oxygen was used. However, phase transformation of -La2S3 to Y -La2S3 progressed preferentially with a decrease in the oxygen content of synthetic ß -La2S3 powder. The Seebeck coefficient of the sintered double-phase Y -La2S3 and -La2S3 was higher than that of the single-phase Y -La2S3, reported previously.Introduction La2S3 exists in three polymorphic forms that are similar to a series of Ce2S3, Pr2S3 and Nd2S3: a, ß , and Y'. The a -La2S3, which is stable at low temperature, is irreversibly transformed to ß -La2S3 of various compositions in the solid-solution range between La2S3 and La3S4, at 923 ± 50K. The -La2S3 may also be an oxysulfide of La10S14O2. Moreover, the ß .-La2S3 phase is transformed to Y -La2S3 ,which has a Th3P4 structure, at 1573 ± 100K. The melting point of Y -La2S3 is 2398 ± 30K where this temperature is similar to those of common refractory materials such as silica and alumina. Therefore, it can be predicted that y -La2S3 which has a high melting point and a thermodynamic stability due to the strong affinity of La for S, would have &high refractory character and chemical inertness in many molten metals. The y -La2S3, colored vivid faint yellow is stable up to 623K in air, where oxidation starts. y -La2S3 is frequently used as pigments for plastics and paints3. Furthermore, Y -La2S3 which is a semiconductor, is considered to be useful as a thermoelectric conversion materials, because it has a high Seebeck coefficient."

Jan 1, 2000

By L. B. Pankratz

High-temperature heat-content values of pure lutetium sesquioxide and dysprosium sesquioxide were measured over the temperature range from 298° to 1,800° K. Similar data for cerium sesquioxide were calculated from measurements of a mixture of cerium sesquioxide and dioxide and known values for cerium dioxide. The results for lutetium sesquioxide are regular. Dysprosium sesquioxide has a minor thermal anomaly near 1,590° K, the extra heat absorption being 220 cal/mole, Hexagonal cerium sesquioxide undergoes a transformation around 1,050° K, which is only slowly reversible; consequently results were obtained for both the low- and high-temperature varieties. The original heat-content data are reported, and smooth values of heat content and the corresponding entropy increments are tabulated. Equations were derived to represent the heat-content values.

Jan 1, 1963