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By John W. Wagner, Robert K. Willardson

Single crystals of Pbl-xSnxTe have been grown from nonstoichiometric, cation-rich melts with the objective of producing as-grown, bulk material containing carrier concentrations ranging from 1016 per cu cm to 1018 per cu cm. Three specific crystal composi-tions were investigated in detail; x = 0.00, 0.10, and 0.17. Pull rates of from I to 3 mm per hr were used. Single crystals were successfully pulled from melts containing as little as 30 at. pct Te. Hall coefficients, resistivities, and carrier mobilities of these materials were determined. The relationship between the composition of the melt and the carrier concentration in the as-grown crystal has been studied for the three crystal compositions of interest. BULK single crystals of Pb,-,Sn,Te have previously been grown from stoichiometric melts.1,2 Such crystals are p-type and have relatively high carrier concentrations ranging from -9 x 1018 per cu cm for PbTe to -8 x l020 per cu cm for SnTe at 77°K. These carrier concentrations result from deviations from stoichiometry (lead vacancies) in the as-grown crystals. Since lower carrier concentrations are desirable for electrooptic device applications, these crystals are usually subjected to long-term, isothermal anneals.' This paper reports on the growth of Pbl-xSnxTe single crystals from nonstoichiometric melts with the primary objective of producing as-grown material containing relatively low (1016 to 1018 per cu cm) carrier concentrations and also reports on the general characteristics of these crystals. The phase relationships in the Pbl-xSnxTe systems are such that materials solidifying from nonstoichiometric, cation-rich melts will have smaller deviations from stoichiometry than materials grown from stoichiometric melts. Fig. 1 is the T-x phase diagram for PbTe in the vicinity of the stoichiometric composition.3 A crystal grown from a stoichiometric melt will solidify at a melting point maximum at which the solid will contain -0.5002 atom fraction of tellurium. PbTe single crystals grown in our laboratories from stoichiometric melts have carrier concentrations of 9 x 10" per cu cm, indicating that the excess tellurium in the crystals is as expected from this phase diagram. However, growth of PbTe from a lead-rich melt will result in material having a more nearly stoichiometric composition. Although the addition of Sn to the melt shifts the solidus curve further toward the tellurium-rich side,4 the general discussion given for PbTe applies to the Pbl-xSnxTe systems as well. EXPERIMENTAL Single crystals of Pb1-xSnxTe have been grown in our laboratories from nonstoichiometric, cation-rich melts using the Czochralski technique and boric oxide liquid encapsulation. The details of the growth apparatus and growth technique have been reported in a previous paper on growth of these alloys from stoichiometric melts.2 In the present study, three specific crystal compositions were investigated in detail; x = 0.00, 0.10, and 0.17. Growth of alloy crystals from nonstoichiometric melts requires considerable care, and good quality single crystals were obtained in this study only by optimizing the mechanical and thermal stability of the growth system and by using pull rates of from 1 to 3 mm per hr (Pbl-xSnxTe crystals are easily pulled from stoichiometric melts at rates of from 5 to 10 mm per hr). The liquid encapsulation technique was found to yield near-ideal conditions, since the B2O3 layer increased the thermal stability at the growth interface, permitted easy attainment of near-ideal thermal gradients, and dampened vibrations at the melt surface. The hygroscopic character of the B2O3 was a slight problem and vacuum heat treating was necessary to completely remove the water from the boric oxide. During initial growth, the seed diameter was reduced and a narrow neck (1 to 2 mm diam) of several millimeters length was grown. The latter steps were found to be necessary for the growth of single crystals, i.e., if either of these two requirements were

Jan 1, 1970

By M. M. Neale

The pottery department has been aptly described as the "heart of the zinc plant," md every operator of a horizontal-retort plant is acquainted with the fact that good retort practice is the keystone of the smelting process. Since retorts and condensers are clay products, it is obvious that improvements in other branches of the ceramic industry should be observed for possible adoption in the pottery process for zinc smelting. Deaeration of clay bodies is one of the improvements that have become fully, established in many brick and pottery plants. Our investigation of a number of these installations always yielded the same answer—improved practice. Improvement in workability, elimination of laminations, less porosity, greater wet and dry strength, were among the claims put forth for this process. All of these features are exceedingly desirable characteristics in the manufacture of a zinc retort. A preliminary test, which involved truck transportation of deaired slugs over a relatively long distance, did show the value of many of these characteristics in forming the retort. Results from the standpoint of , longer retort life in the smelting furnace were not outstanding. The idea lay dormant for several years but was revived again in 1940, when it was decided to make whatever changes were necessary in the equipment for pottery manufacture to fully demonstrate the process. A number of the manu- facturers of machinery for clay work were asked to submit proposals, and the plan finally adopted was extremely simple and economical. Machine FOR DeaeRRATING Selection of the ''Straight-line'' principle for conversion of the "Wettengel" pug mill to a ''vacuum-extrusion" machine preserved some usable parts of the original equipment, such as the drive mechanism, and main shaft. The converted machine consists of a feed hopper, a compression and shredding zone, a vacuum chamber, and an extrusion barrel, as shown in Fig. I. In operation the clay mix travels from the feed hopper into the compression zone, where it is compressed and finally forced around the tapered cone into the vacuum chamber. As it enters this chamber the clay body is shredded into thin plates, for exFosure to the vacuum. The shredder consists of a hub mounted on the main shaft, to which are bolted segmental sections, each of which carries shredder knives. The compression zone and extrusion barrel function as seals for the vacuum chamber and the shredded clay mix is agitated thoroughly during its exposure to the vacuum. A vacuum pump, equipped with a 3-hp. motor, is attached to this chamber, and maintains 25 to 26 in. vacuum during operation of the mill. Changes in Practice Prior to the adoption of the deaeration process, our standard pottery practice called for double mixing in the combination 7

Jan 1, 1944

By R. L. Dietrich

[ ] We at The Dow Chemical Co. have recently done some work on the deformation of magnesium alloys and although it is far from complete there have been a few observations which may be of interest in connection with this paper. In the first place, I should like to point out that the deformation of polycrystalline magnesium alloys has not been completely explained by the work on single crystals. Bakarian and Mathewson found slip on the ( 101) and {002) planes, and (102) twinning as the deformation mechanisms in magnesium single crystals, but in compression when the (002} planes were within ii° of parallel t0 the compression surfaces, fracture occurred at all temperatures up to 340°C (644°F). In commercial working processes, particularly in rolling, an orientation is quickly produced which should be unfavorable to further deformation by the three established mechanisms. The first few reductions in rolling quickly produce an orientation having

Jan 1, 1947

By J. S. Kirkaldy, W. V. Youdelis

THE occurrence of concentration distributions in rapidly cooled castings with gradients of opposite sign to those expected on the basis of the constitution diagram and diffusion controlled kinetics, has long interested metallurgists. The work on inverse segregation to 1937 has been adequately reviewed by Vaughan, and to 1949 by ell-walpole. The general conclusion for unidirectional solidification, that the enrichment of the initially solidifying regions with lower melting point compositions is due to the flow-back along interdendritic channels of normally segregated residual liquid, has a very sound experimental basis. Perhaps the best experimental work and the most complete qualitative description of the process has been given by Adams.3 The authors accordingly assume the reader's understanding of the content of this paper. It appears that one of the principal deterrents to the complete understanding of the process has been the lack of an analytical description. Although a number of workers including Masing,4-6 Sauerwald,7 and Adams3 have attempted quantitative predictions,

Jan 1, 1959

By John P. Bingham

GRACE mine and mill, owned by Bethlehem-Cuba Iron Mines Co. and operated by Bethlehem Cornwall Corp., are being developed to produce 9600 tons of 42 ½ pct Fe magnetite ore, to yield 5760 tons per day of agglomerated iron concentrates averaging 65 pct Fe. Located about 14 miles south of Reading, the property is ideally situated in relation to good highways and railroad. Three major steel plants, at Bethlehem, Steelton, and Sparrows Point, Md., are about equidistant from the mine. Discovery of the orebody resulted from an airborne magnetometer survey, completed in 1948, con¬sisting of 7000 lineal miles of flight lines spaced one-fourth of a mile apart and extending from the Delaware River on the east to Gettysburg, Pa., on the west. After examining the magnetic maps, Bethlehem's geologists made limited surface traverses over the Grace mine and Warwick area to check the location, and realtors were engaged to purchase the desired properties over and adjacent to the area showing favorable indication of ore.

Jan 1, 1957

By Orville A. Derby

In view of the recent important discussions before this Institute on the genesis of metalliferous deposits, certain features in the occurrence of gold which seem to be more clearly developed in Brazil than elsewhere can hardly fail to be of interest. As the observations here recorded have necessarily been of a somewhat cursory character, they will be presented in the form of brief notes, without any attempt to draw conclusions as to their genetic significance. Gold in Gneiss.—The statement made by me many years ago† that in the districts of Campanha and S?o Gongalo, in southern Minas Geraes, gold occurs in gneiss, can now be reaffirmed in the most positive manner, on the strength of a recent examination of fresh material, confirmed by the testimony of an experienced mining captain from the Morro Velho mine, who, being skeptical on this point, made a prospectingtour in the district. The specimens examined, though so far decomposed as to be readily disaggregated, were clearly of

Jan 1, 1903

By Klaus Schonert

The elements of a mill matrix and the classifier matrix de- scribing the grinding process depend on operating conditions, especially on the feed rate. Relationships between the matrix elements and the feed rate have a great influence on the stability of a closed circuit and its optimum point. These problems have been studied by means of computer simulation and different kinds of classifier characteristics have been considered. A circuit with a cross stream classifier has only a limited range where stable operation condition can be attained. Beyond the stable limit, the recirculation ratio increases rapidly and there is no correlation between feed rate of the circuit and feed rate of the mill. In comparison, a spiral stream classifier gives a wide range of stable operation. The recirculation ratio can be greater than in the case of the cross stream classifier if the feed rate is small. The results of the simulation provide a better understanding of the real behavior of closed circuit grinding.

Jan 1, 1969

By C. G. Dunn

The measurement of interfacial teusions or grain boundary energies in metals is an important metallurgical problem, especially since it bears on growth and nucleation processes. Statistical methods of measuring equilibrium grain boundary angles, which relate interfacial tensions, have been used by some investigators1'2 but more direct methods would be preferred. A direct way, based on a simple extension of a successful method of growing single crystals of silicon ferrite to predetermined orientations in flat specimens,3 is to produce three-grain specimens in such a way that the equilibrium common grain boundary will be perpendicular to the surface of the specimen. The angles to be measured then appear as the grain boundary angles in the surface of the specimen. The method of producing a single crystal specimen with a predetermined orientation is basically the same as that employed by Yoshida and Fuji-wara4 in their work on aluminum wires. The specimen, prior to any single crystal transformation, must have a matrix which will support the growth of a crystal of the desired orientation. Growth may occur through exaggerated grain growth or, if the matrix is strained a critical amount. by normal recrystallization. In either case the matrix must have stability at the temperature used to effect the transformation, this stability appearing as a long induction period for exaggerated grain growth or for the formation of recrystallization nuclei. Additional control is gained by using a high temperature gradient through which the specimen is moved at a suitable rate. To obtain the desired orientation, the specimen is fed a short way into the furnace producing one or more crystals in the hot end. After the specimen is removed from the furnace, the orientation of a crystal is determined, so that this crystal may be reoriented by properly deforming a narrow piece of the matrix between the end crystal and the rest of the specimen. This part of the specimen in the case of silicon ferrite is preferably held at red heat during the reorienting process. Fig 1 shows a specimen which is ready to be transformed into a single crystal through growth of a reoriented "seed" crystal. When the method just described is applied to the production of a three-grain specimen two crystals are grown first side by side in one end, the specimen is then reversed and the third grain grown from the opposite end. A suitable group of grains each of different orientation is one where all three grains have the same crystallo-graphic plane in the plane of the specimen. Fig 2 shows a photograph of a three-grain group prepared as described. The notches are introduced in the open ends of the grain boundaries to anchor them during the final annealing operations which ultimately should bring the grain boundaries to the lowest energy configuration. Two-grain groups with different crystallographic planes in the plane of the specimen can be similarly prepared and treated. If the two grains have different surface (gas to metal) energies per unit area, the equilibrium condition leads to a curved grain boundary.* * This feature of the problem was pointed out by J. c. Fisher. References 1. Cyril Stanley Smith: Grains. Phases and Interfaces: An Interpretation of Microstructure. Trans. AIME 175, 15. Met. Tech. TP 2387, June 1948. 2. D. Harker and E. Parker: Grain Shape and Grain Growth. Trans. A.S.M. (194,5) 34, 156-195. 3. C. G. Dunn, A. Seddon, and R. Wylie: Unpublished Work, 1946-1947. 4. Takeo Fujiwara: A Method of Producing A Long Single-Crystal Wire of Aluminum with any Desired Crystallographic Axis. Jnl. of Sci. Horoshima Univ. A, (1939) 9, No. 3, 227.

Jan 1, 1950

By R. Q. Shotts

Data are presented which show that fractions of varying densities from the same coals are oxidized at different rates by nitric acid. From oxidation data, the approximate quantity of "bright" and "dull" components may be calculated. Definite relationships between oxidation rate and rank are shown for density fractions from at least two bituminous coals. IN 1945, the Alabama State Mine Experiment Station initiated a program on the determination of fusain in certain coals of the state.1 Because of the lack of equipment and personnel necessary for microscopic examination, the chemical method2 was used exclusively. During studies of the distribution of fusain in fractions of various sizes and densities on a medium volatile coal, the author noted a higher rate of oxidation of the nonfusain part of the coal in the lower density fractions and the difference in rate became more marked the shorter the oxidation period used. Since durain and other "dull" components of coal have been reported3,4,5 to have higher densities than vitrain and the bright components, it appeared probable that the observed differences in rates of oxidation in the different density fractions were due to variations in petro-graphic composition. Such effects have been noticed by other workers.2,3 In order to obtain further evidence on this point, several Alabama coals of different rank have been separated into three or more fractions on the basis of density and their rates of oxidation determined, using the procedure specified for the determination of fusain, except that measurements were made at short time intervals as well as for the longer periods specified in the regular procedure. Significant differences in the rates of oxidation of the nonfusain part of the various fractions have been observed, and it is believed that studies of this type may make possible the identification of individual petrographic components or lead to methods for their semiquan-titative estimation. Properties of the Coals: Analyses and some properties of the whole coals studied are given in table I. The range in rank of the coals is not the widest possible within the state, but samples of the low volatile coals that occur in thin beds in the northeastern part of the state, were unavailable. The Clements bed is not, at present, considered workable. The coal is of medium volatile rank, quite friable, and very strongly swelling. Analyses of different size fractions show that the larger sizes are of higher rank than the smaller ones. Material passing the No. 50 sieve (all sieve sizes refer to the U. S. Standard Series) is close to high volatile A in rank, except for the size passing a No. 200 sieve, in which fusain is partially concentrated. Because of the variation in rank of the sizes of Clements coal, oxidation studies were made of two widely different size ranges. The + 1-in. material was crushed on rolls to about 1/8 in. and separated into five fractions by float-and-sink treatment in a benzene-carbon tetrachloride mixture. The — No. 4 + No. 8 and the — No. 4 + No. 50 size ranges tested overlap but the latter size was studied last with the expectation that it would include more oxidizable material than the first size. This proved not to be the case. Yields and properties of the specific gravity fractions oxidized are shown in table II. Milldale bed coal probably represents, as nearly as it is possible to do so, the "average" coal of the state. The material passing a No. 4 sieve was the only size range oxidized. It was divided into four specific gravity fractions. As in every case the heaviest fraction, which was essentially rock, was discarded. The Black Creek is the most extensive in area of

Jan 1, 1951

By R. Q. Shotts

Data are presented which show that fractions of varying densities from the same coals are oxidized at different rates by nitric acid. From oxidation data, the approximate quantity of "bright" and "dull" components may be calculated. Definite relationships between oxidation rate and rank are shown for density fractions from at least two bituminous coals. IN 1945, the Alabama State Mine Experiment Station initiated a program on the determination of fusain in certain coals of the state.1 Because of the lack of equipment and personnel necessary for microscopic examination, the chemical method2 was used exclusively. During studies of the distribution of fusain in fractions of various sizes and densities on a medium volatile coal, the author noted a higher rate of oxidation of the nonfusain part of the coal in the lower density fractions and the difference in rate became more marked the shorter the oxidation period used. Since durain and other "dull" components of coal have been reported3,4,5 to have higher densities than vitrain and the bright components, it appeared probable that the observed differences in rates of oxidation in the different density fractions were due to variations in petro-graphic composition. Such effects have been noticed by other workers.2,3 In order to obtain further evidence on this point, several Alabama coals of different rank have been separated into three or more fractions on the basis of density and their rates of oxidation determined, using the procedure specified for the determination of fusain, except that measurements were made at short time intervals as well as for the longer periods specified in the regular procedure. Significant differences in the rates of oxidation of the nonfusain part of the various fractions have been observed, and it is believed that studies of this type may make possible the identification of individual petrographic components or lead to methods for their semiquan-titative estimation. Properties of the Coals: Analyses and some properties of the whole coals studied are given in table I. The range in rank of the coals is not the widest possible within the state, but samples of the low volatile coals that occur in thin beds in the northeastern part of the state, were unavailable. The Clements bed is not, at present, considered workable. The coal is of medium volatile rank, quite friable, and very strongly swelling. Analyses of different size fractions show that the larger sizes are of higher rank than the smaller ones. Material passing the No. 50 sieve (all sieve sizes refer to the U. S. Standard Series) is close to high volatile A in rank, except for the size passing a No. 200 sieve, in which fusain is partially concentrated. Because of the variation in rank of the sizes of Clements coal, oxidation studies were made of two widely different size ranges. The + 1-in. material was crushed on rolls to about 1/8 in. and separated into five fractions by float-and-sink treatment in a benzene-carbon tetrachloride mixture. The — No. 4 + No. 8 and the — No. 4 + No. 50 size ranges tested overlap but the latter size was studied last with the expectation that it would include more oxidizable material than the first size. This proved not to be the case. Yields and properties of the specific gravity fractions oxidized are shown in table II. Milldale bed coal probably represents, as nearly as it is possible to do so, the "average" coal of the state. The material passing a No. 4 sieve was the only size range oxidized. It was divided into four specific gravity fractions. As in every case the heaviest fraction, which was essentially rock, was discarded. The Black Creek is the most extensive in area of

Jan 1, 1951

By H. L. Lovell, L. H. E. Weyher

Cyclones have been used successfully in the mineral industries to solve solid-liquid as well as solid-solid separation problems in the processing of fine particles. Substantial information is available about the operation of cyclones as thickeners, classifiers, and concentrators using a dense medium. However, very little is known about the operation of the cyclone as a fine coal concentrator not using dense medium. This application of the cyclone, namely to wash fine coal in water, requires that classification phenomena be minimized in order to arrive at an effective separation of the high density ash and sulfur-bearing mineral particles from the low density coal particles over a wide particle size range. The authors have investigated the role of feed pressure, orifice diameters, and vortex-finder length in the cyclone washing of fine coal (--1/4 in.) in water. The results of this investigation show that cyclone washing of fine coal in water is an effective unit operation particularly capable of reducing the inorganic pyritic sulfur content. The combination of hydrocyclones with complimentary equipment such as Sieve bends, shaking tables, and flotation units appears to be especially promising and may ultimately yield fine coal processing systems that could approximate the high recovery efficiencies of today's coarse coal cleaning circuits. In the future, fine coal beneficiation can be expected to receive even greater research emphasis as a result of increasing sulfur restrictions on all major coal markets. In a previous paper, work, conducted at the Pennsylvania State University, on the hydrocyclone washing of fine coal was discussed.' The initial evaluation based on that wo-rk demonstrated the feasibility of hydrocyclones as fine-coal cleaning devices, and in that previous paper selected test data were presented that showed in principle how product yield and assay respond to variations of the major cyclone operating variables. The present paper reports in greater detail on the findings and presents a comprehensive evaluation of the data as follows: (1) Hydrocyclone throughput rates were related to feed pressure and other variables by regression equations. These equations are compared with other capacity-vs.-pressure drop expressions taken from the literature on classification cyclones. (2) The flow ratio was found to be the most important variable for the separation of the solids. Control of this ratio through various cyclone operating parameters is discussed. (3) The data on the product yield as well as the ash and sulfur assays from the tests were evaluated by means of correlation and multiple regression analyses. Because size-classification phenomena cannot be suppressed completely in hydrocyclone washers, product yield and assay data are regressed against cyclone operating variables separately for different size classes. These equations then reveal how the interactions of the cyclone operating variables vary in terms of the separation for different size classes. (4) Density partitions from additional tests were analyzed by supplementing product-size analyses with sink-float analyses of the separated product size classes. The evaluation of these data show how classification phenomena affect separation by density. The results demonstrate in particular the feasibility of the hydrocyclone washer for removing pyritic sulfur from fine coal. In addition to these specific findings, the investigation points up the value, in general, of using hydrocyclone washers in combination with unit operations such as screening, table concentration, and flotation. In order to make optimum use of the hydrocyclone washers and work out the most effective combination of unit operations, it is important to have careful flowsheet analyses corresponding to the given feed and product requirements. Analyses of this kind are now possible by means of computer simulation of flowsheets and other operation research tools. INTRODUCTION Before proceeding with the detailed treatment and evaluation of our results, it will be useful to review the fundamental aspects of cyclone separators and also restate the experimental procedures and data handling employed in these studies. Review of Cyclone Fundamentals: AS shown in Fig. 1, the basic components of cyclones commonly used

Jan 1, 1970

By C. F. Rust

Experimental evidence is presented showing that reproducible formation resistivity factor measurements and resistivity index determinations on reservoir core samples map be made utilizing either the two- or four-electrode methods. Equipment is described which permits the application of either technique to the core specimen without loss of time and with a minimum amount of effort. Since electrical resistivity measurements on reservoir rocks are important not only in electric log interpretations, but also in the study of fundamental rock parameters, it was considered desirable to compare the applicability of both techniques of resistivity measurement. INTRODUCTION The techniques employed in the measurement of electrical resistivity on reservoir rocks, as practiced in the petroleum industry, may be reduced to two fundamental methods: one utilizing two electrodes only, usually referred to as the two-electrode method; the other using two additional electrodes and commonly known as the four-electrode method. In the former, the core sample whose resistivity is to be measured is mounted between two electrodes, usually metal discs, which serve to pass a current of known magnitude through the saniple. The potential drop across the sample, measured between these same two electrodes, and the core dimensions furnish the necessary data to compute he resistivity of the sample. In the four-electrode technique the end plates, again usually ol metal, still serve as current electrodes. Additional probes or electrodes dispersed along the sample are utilized to measure the potential drop. Both methods are used in practice1,2 and it is the purpose of this paper to compare the two techniques as applied to the determination of formation reiistivity factors and the resistivity index exponent n, in Archie's empirical equation I = p/po = Sw 11. To evaluate the two techniques it is desirable to point out the experimental precautions which must be taken to insure reliable results. It is evident from the electrode arrangements of the two- and the four-electrode methods that, for a given sample, the volume of sample included by the four-electrode method is less than the volume included by the two-electrode method. One of the prime difficulties associated with the two-electrode method is the possible occurrence of an abnormally high resistance between the electrodes and the brine-saturated sample, which results in erroneous resistivity values for the core sample itself. Attempts to alleviate this difficulty meet varying degrees of success. Methods used in the past employ such absorbent materials as brine-saturated Kleenex: chamois, or felt. A technique described by Morgan, Wyllie, and Fulton,1 appears to be more satisfactory. Their method consists of spraying or painting the end areas of a core sample with conductive silver paint. This technique reduces contact resistances between the porous medium and the electrodes to a value which is generally negligible as compared to the resistance of the sample itself. In the four-electrode method these requirements are not as stringent since separate probes are used to measure the potential difference acrozs a portion of the sample. In this case, contact resistance occurring at the current electrode; are of no consequence. and those appearing at the potential

Jan 1, 1952

By F. W. C. Boswell, R. L. Cunningham, H. M. Weld

Chemical analysis shows the partition of the magnesium addition between the metal and the graphite is independent of whether the graphite is in the form of nodules or flakes. The bright central spot observed in nodular graphite polished sections is shown to be due to the structure of the nodules. DURING the past few years numerous papers have been published on the production1-7 and heat treatment" of nodular cast irons. However, very little information is available on the structure of the nodules and the reason for their formation. It would appear that an explanation of the phenomenon of nodulation must await a detailed knowledge of the nature of the nodule. Disagreement exists among various workers on such a fundamental point as to whether or not a nodule actually contains a microscopically visible, nongraphitic nucleus.9-11 Work was initiated with a view to obtaining definite information on this and other aspects of the problem. Chemical Separation and Analysis Microscopic appearance had indicated9-11 that a nongraphitic core might exist in nodules (Fig. 1). It appeared that a chemical comparison of separated nodules and flake graphite would be profitable, for if the core is nongraphitic a relatively large amount of certain elements would be found in the nodules as compared to the flake. This comparison could best be made by obtaining nodules and flake from the same melt of cast iron, part of which had been in-noculated with a suitable addition reagent for the formation of nodules. A 300 lb melt was produced. About half of this was innoculated in the ladle with an Fe-Si-Mg alloy to produce nodules and cast into keel blocks; the remaining half of the melt had silicon added in an effort to compensate for the silicon in the innoculant used in the other half of the melt and this was cast into similar keel blocks. The analyses of the resultant irons are given in Table I. Nodules and flake were chemically extracted from 2 kg samples of metal as described in the appendix. While this method dissolved the iron and chromium carbides, it did not dissolve the titanium, vanadium, and molybdenum carbides. These latter carbides could have been removed by nitric acid, but in other experiments it was found that it attacked pools of metallic iron entrapped in the nodules which had, until the nitric acid treatment, been protected from the attack of the sulphuric, hydrochloric, and hydrofluoric acids. It will be shown in the next section that entrapped iron exists in nodules but not in flake. On microscopic examination many tiny irregular particles were observed to accompany both the nodules and the flake. These were identified by tabling a sample of nodules from which a sufficient fraction was obtained for X-ray analysis. A good pattern of titanium carbide was obtained indicating that this was the predominant compound present. Since it was not possible to determine how completely the carbides could be removed mechanically and since their removal from flake is much more difficult, it was decided not to resort to any separation as this would render further comparisons more difficult. The samples were ashed in a combustion

Jan 1, 1953

By Joseph Pogue

IT is well known that one of the cornerstones of economic theory is the so-called law of supply and demand, which, really, is a group of economic laws, one of which may be succinctly stated A rise in price tends, sooner or later, to increase supply. It is the fear that, in the case of petroleum, a limited' natural resource, a point will soon be reached when supply will not respond adequately to price advances, which in recent years has prompted a movement for oil conservation. This movement has lately taken concrete shape in the appointment of 'a Federal Oil Conservation Board by the President. An important aspect of the law of supply and demand is that the supply of any commodity, is not an entity per se, but is a factor of price. Supply, without the specification of, price, has no exact meaning; and, in practice supply cannot be divorced from considerations of price. Mathematically, supply may be expressed by the formula SP, which means that supply varies with price, just as the value of 10 raised to the x power varies with x. In its technical usage, supply is the, quantity of a commodity that is bought currently on the market at a given price. In the case of a natural resource, however, this quantity will eventually depend not alone on price but on the physical volume of the reserve that exists and that, in consequence, can respond to the stimulus of price. If this reserve is fixed in size, we must sooner or later reach a point where supply can no longer respond to price in the usual degree and a permanent shortage will develop which no advance in price can correct, except in so far as higher prices may curtail demand or improve the efficiency of utilization. This statement brings us to the examination of amore fundamental aspect of the law of supply and demand as applied to natural resources; namely, that natural-resource reserves are not fixed in size: just as the current supply of a natural-resource commodity is a function of price, so its reserve is likewise a resultant of price. Natural-resource reserves; therefore, have no exact meaning without the specification of price, and in practice their measurement. cannot be divorced from considerations of

Jan 3, 1925

By E. F. Jr. Young, H. E. Steinman, G. C. Smith

Through a progressive laboratory and pilot-plant program Jones & Laughlin Steel Corp has analyzed and corrected mine drainage pollution problems at all of its coal mines. In conducting this program, the company found no "typical" drainage discharge. Each discharge point at each mine was unique, so that varied approaches were needed to eliminate stream pollution. To illustrate the variety of these approaches, the treatment of drainage from foul, discharge points at three mines in Pennsylvania will be considered here. The flows and critical analyses of the drainage sources and treated effluents arc shown in Table I. Hydrated Lime Works at Thompson Borehole The discharge stream from the Thompson bore- hole at the Vesta No. 5 mine flowed into a small branch creek where it created a "yellowboy" deposit and affected aquatic life. Investigation indicated that hydrated lime would neutralize the acid and precipitate ferric iron without aeration. Treatment of the 150.000-gpd flow, however, created about 4000 gpd of wet sludge for which there was no nearby accumulation site. With State approval, this sludge was deposited through an unused borehole into an abandoned section of the Vesta No. 6 mine several miles away.

Jan 1, 1970

By Harold Margolin, W. R. Hibbard, R. W. Fenn, H. P. Moore

Deformation lines, also called etch markings or strain markings, are non-effaceable lines developed in individual grains by etching a metal specimen which has been cold worked sufficiently to cause atomic non-conformity or slight orientation differences within the grains. Etching occurs more rapidly at these lines of high chemical reactivity to produce a result similar to that revealing grain boundaries. Wider etching effects forming bands have been found. They are believed to be bands of deformation lines which form areas of measurably different orientation from the crystal matrix. The crystallite rotations causing these bands have been shown by Barrett2 to contribute to deformation textures. Although deformation lines have been observed in many metals, the amount of deformation requireti for their appearance has been established only in general terms. Mathewson and Phillips3 observed the first appearance of deformation lines in cold-rolled alpha brass at about 20 pct reduction in thickness using the standard ammonium hydroxide hydrogen peroxide etchant. Price and Davidson4 noted defor- mation lines in common high brass after 26.5 pct reduction by cold rolling using the same etchant. Johnson6 observed dark thick forklike lines in 99.99 pct pure copper reduced 31.8 pct. Adcock6 observed deformation lines in 80-20 copper-nickel alloy rolled 50 pct. Samans7 found no deformation lines in alpha brass single crystals cold rolled 9.5 pct but they did appear after 25 pct reduction using ammonium hydroxide and hydrogen peroxide etchant. Barrett and Levenson8 observed deformation bands in drawn polycrystalline iron at very small reductions in area and noted that their initial appearance perhaps depends on grain size and other conditions. They reported deformation bands in a single crystal of iron reduced 6 pct by drawing. Brickg noted that deformation lines in 70-30 brass apparently associated with I I I I ) planes appeared after reductions of from 20-50 pct by cold rolling. Brick and Williamson10 noted that in single crystals of 70-30 alpha brass "as in polycrystalline brass, no deformation markings appeared until reductions exceeded 20 pct." Cook and Richards" reported that in Copper cold rolled less than about 50 Pet few strain markings were apparent but for higher reductions many strain markings appeared transverse to the rolled direction. In a review article Brick and Phillips12 noted that previous studies had not shown deformation lines in cold rolled alpha brass below 20 pet reduction and added that 4

Jan 1, 1949

By H. P. Moore, R. W. Fenn, Harold Margolin, W. R. Hibbard

Deformation lines, also called etch markings or strain markings, are non-effaceable lines developed in individual grains by etching a metal specimen which has been cold worked sufficiently to cause atomic non-conformity or slight orientation differences within the grains. Etching occurs more rapidly at these lines of high chemical reactivity to produce a result similar to that revealing grain boundaries. Wider etching effects forming bands have been found. They are believed to be bands of deformation lines which form areas of measurably different orientation from the crystal matrix. The crystallite rotations causing these bands have been shown by Barrett2 to contribute to deformation textures. Although deformation lines have been observed in many metals, the amount of deformation requireti for their appearance has been established only in general terms. Mathewson and Phillips3 observed the first appearance of deformation lines in cold-rolled alpha brass at about 20 pct reduction in thickness using the standard ammonium hydroxide hydrogen peroxide etchant. Price and Davidson4 noted defor- mation lines in common high brass after 26.5 pct reduction by cold rolling using the same etchant. Johnson6 observed dark thick forklike lines in 99.99 pct pure copper reduced 31.8 pct. Adcock6 observed deformation lines in 80-20 copper-nickel alloy rolled 50 pct. Samans7 found no deformation lines in alpha brass single crystals cold rolled 9.5 pct but they did appear after 25 pct reduction using ammonium hydroxide and hydrogen peroxide etchant. Barrett and Levenson8 observed deformation bands in drawn polycrystalline iron at very small reductions in area and noted that their initial appearance perhaps depends on grain size and other conditions. They reported deformation bands in a single crystal of iron reduced 6 pct by drawing. Brickg noted that deformation lines in 70-30 brass apparently associated with I I I I ) planes appeared after reductions of from 20-50 pct by cold rolling. Brick and Williamson10 noted that in single crystals of 70-30 alpha brass "as in polycrystalline brass, no deformation markings appeared until reductions exceeded 20 pct." Cook and Richards" reported that in Copper cold rolled less than about 50 Pet few strain markings were apparent but for higher reductions many strain markings appeared transverse to the rolled direction. In a review article Brick and Phillips12 noted that previous studies had not shown deformation lines in cold rolled alpha brass below 20 pet reduction and added that 4

Jan 1, 1949

By Carl Samans

IN their recent complete review of the subject of age-hardening,1 R. F. Mehl and L. K. Jetter classify the main types of precipitation-hardening alloys under two headings, depending upon the nature of the precipitate and the character of the precipitation. In the alloys falling under the first heading, which display "continuous precipitation" and are typified by the aluminum-copper alloys, "precipitation seems to occur without much regard to grain boundaries and apparently at much the same rate at every point," although an acceleration in regions plas-tically deformed has definitely been established .2 In the second type of alloys the precipitation is "discontinuous," as in the copper-silver system for example, and "seems to start in restricted regions, primarily those contiguous with the grain boundaries, and to spread inward in an advanc-ing wave." The reasons for the occurrence of these two greatly different types of precipitation are unknown, as are those for many other reactions that take place in the solid state. In the present paper only the first or "continuous" type of precipita-tion will be dealt with, for which a complete crystallographic mechanism has been worked out for the process of precipitation from a supersaturated solid solution of copper in aluminum. Based upon this mechanism, an explanation of the various property changes found experimentally will be developed in the second paper of this series. In later papers "dis-continuous precipitation" in copper-silver alloys will be explained, and an effort will be made to rationalize the two processes and types of precipitation.

Jan 1, 1940

By S. F. Emmons

THE first paper which appears in the published Transactions of our Institute is that read by our respected Secretary at its first meeting in Wilkes-Barre, in May, 1871. It is entitled The Geological Distribution of Mining Districts in the United States, and presents a brief but masterly review of what was known of the distribution of our deposits of useful minerals, particularly the metals, not only from a geographical but from .a geological stand-point. At the request of Dr. Raymond, I agreed, somewhat hastily, perhaps, to write for this occasion a brief sketch of the geological distribution of the deposits of the useful metals in this country, in the light of the increased knowledge of the present day. In the time given no personal investigation was possible, and as it was therefore out of the question to attempt to make anything that could be considered an original contribution to the history of our ore-deposits, I have been obliged to limit myself to an examination of such published data within my reach as bore upon this subject, and could be consulted in the brief time I have been able to give to it. Had the geological investigations undertaken by the Tenth Census been continued systematically by the United States Geological Survey or by the Eleventh Census, it might have been possible to make a fairly-complete review of the subject. As it is, the principal result of my examination 1 has been to show how very unequal

Jan 1, 1913

By Edward A. Vitunac

The emerging importance of pneumatic conveying systems for bulk materials is largely due to the economic advantages such systems frequently exhibit when compared to alternate methods. Included in these advantages are relative simplicity, ease of installation, flexibility, ease of maintenance, cleanliness, safety and ease of automation to the degree desired. In general, installed costs favor a pneumatic system when compared to competing mechanical systems if the transporting distances are long or to and from many points. In addition, supplemental use such as cooling, heating, or drying may supply the incremental value required to justify its selection.1 The main disadvantages of a pneumatic system are the greater horsepower required per unit weight of material conveyed, material limits in abrasiveness, and density. In addition, material breakage tends to increase at changes of direction and at any obstruction such as that caused by the imperfect butting of two pipe sections in the conveying line. Classification of the material at the discharge may also cause problems in dusting and segregation. Materials weighing less than 4 lb per cu ft tend to cause feeding and collecting problems although they can be conveyed easily. Material between 4 lb and 20 lb per cu ft can be handled with fewer problems, but flow rate is hard to predict. The 20-60 lb per cu ft range offers best results, whereas materials of over 60 Ib per cu ft tend to drop out of the air stream and settle in the pipeline unless careful pro- visions are made to prevent this.2

Jan 5, 1968