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By Oliver S. North

Reserves of perlite rock in the western section of the United States are immense. A geological report prepared for the Union Pacific RR showed proved tonnage of over 400 million tons in southern Nevada alone. Yet the perlite industry is not large, and most of the mines are relatively small. There are indications that perlite processing, thus far largely in the hands of relatively small com¬panies, is becoming concentrated in a few large companies. For economic reasons the bulk of perlite sold in crude form has come from three or four pro¬ducers, although many individual operators have sold small quantities to limited lists of purchasers. Perlite is one of ultra-lightweight aggregates. Owing to its outstanding qualities as an aggregate, variety of uses, and ultimate economy of use, it has enjoyed considerable popularity in this country in recent years. Marked foreign interest also has been evinced in this material.

Jan 2, 1955

By A. M. Turkalo

IT is a well-known fact that martensitic steels show a greater resistance to brittle fracture than do pearlitic and bainitic steels. It was, therefore, thought worthwhile to investigate the mode of brittle fracture with respect to structure by studying the effect of various austenite decomposition products on the propagation of brittle fracture in steel by means of electron microscopy. Newly developed replication techniques together with the advantages of the electron microscope such as great depth of field, available high magnification and easy adaptation to stereophotography make electron microscopy very suitable for fracture studies. EXPERIMENTAL PROCEDURE An essentially plain carbon steel containing 0.56 pct C, 1.30 pct Mn, 0.02 pct P, 0.03 pct S and 0.22 pct Si was used in this investigation. The following table gives the heat treatments used to obtain the various austenite decomposition products: The resulting austenite grain size from the 870°C austenitization treatment was about an ASTM No. 7 grain size. The specimens which were 2 in. long, 1/4-in. diam bars were austenitized in a tube furnace through which argon gas was blown. The tube was not, however, air-free and the specimens were not completely oxide-free. Isothermal treatments were done in a lead bath. With the exception of the fully hardened specimen and the one as-isothermally transformed at 300°C the heat treated specimens were notched in the following fashion with a jeweler's saw. A cut about 0.08 in. deep was made perpendicular to the length of the bar. The specimen then was rotated about 45 deg and another cut about 0.08 in. deep was made. In the case of the hard martensitic and bainitic specimens, only one cut was made and the depth was not controlled. The design of the two-cut notch caused fracture to initiate at the point of intersection of the two saw cuts. The specimens were broken at -196°C in a Charpy impact testing machine. In order to hold the specimens securely in the impact machine two square pieces of mild steel were made about 5/8 in. long having the same cross section as that of a standard Charpy specimen but containing a hole 1/4 in. diam through the center of the cross-section. These adapters were slipped over the ends of the test specimen which was then secured tightly by means of set screws in the adapters. The specimen with the adapters was cooled to -196°C in liquid N,, then placed in the impact machine and broken within 3 sec. One half of the broken specimen was used for the electron microscope study of the actual fracture surface. The other half was nickel-plated and a cross section through the notch and fracture was polished for electron microscope examination. Carbon replicas of the fracture specimens for the electron microscope study were made essentially according to Bradley's evaporation technique.' Both direct carbon and two-stage carbon replication techniques were used. In the case of the direct carbon technique, a thin layer of carbon was evaporated first at an angle of about 45 deg to the mean fracture surface and then another film of carbon was evaporated normally to the fracture surface. The carbon replica was freed electrolytically.2 The specimen was made an anode in a 10 pct Nital polishing solution. It was etched intermittently by shutting off the power now and then. The freed replica was washed in 40 to 50 pct water solution of nitric acid for 10 min or so, then washed in water and picked up on a screen for examination. The two-stage carbon replication technique involved first making a primary replica of cellulose * acetate from which a carbon replica was then made. One side of a strip of cellulose acetate wet with acetone was pressed lightly against the surface of the specimen, allowed to dry and then stripped. Prior to the deposition of carbon, which was done at 90 deg to the cellulose acetate replica surface, chromium was evaporated at 45 deg. After the carbon evaporation the cellulose acetate was dissolved in acetone according to the Jaffe method3 leaving the carbon replica preshadowed with chromium for examination.

Jan 1, 1961

By J. A. Roberson, Robert A. Rapp

From the observation of platinum wire marker movement in the oxidation of columbium at high lemperatures and low oxygen pressures, predonzinant cation diffusion in CbO, has been demonstrated. The Cu,0 molecule was used as an oxidizing species to study the nature of the porous scale and the location of the reduction site in the oxidation of colum-bium. The Cb205 scale contains microporosity and forms by alternate ionic diffusional growth and fracture. The oxidation of columbium at high temperatures and very low po, results in a relatively compact and protective Cb205 layer. THE observation of marker movements during oxidation is one means for the identification of the mobile ionic species in an oxide lattice. Previous marker experiments in the oxidation of columbium have all resulted in the markers being found on the outside surface of the Cbz05 scale. The Cr203 powder markers of Klopp et a1.,' the gold film marker of Kofstad and ~jijllesdal,' and the platinum wire marker of Cathcart et a1 .3 were found at the oxide/gas interface for oxidation temperatures ranging from 450" to 120O0C. However, in all experiments relatively high oxygen pressures were used. As discussed by Mrowec, even the interpretation of marker experiments in simple scales containing only one compound is not without ambiguities. In brief, it can be said that a marker may be found almost anywhere in the scale layer if the metal oxidizes by cation diffusion through the scale; the position of the marker depends upon morphological happenings in the scale. When considering marker movement in a polyphase scale one must proceed with extreme caution. For example, in the past (and present) work markers have never been found at the columbium-scale interface, and one might infer that the oxygen ion is mobile in CbO and CbO,. However, only trace quantities of CbO and CbOz have been present on any of the specimens, so no firm statement is justified on this basis. Despite previous experimental work, considerable doubt still exists concerning the role of the oxides CbO and CbOz in the oxidation of columbium. The identification of the mobile ionic species in CbO and CbOz from the observation of platinum wire markers was one goal of the present investigation . The linear kinetics of columbium oxidation at high temperatures (T - 1000°C) suggests that the Cbz05 scales which form on columbium are porous. From mercury absorption measurements on a Cbz05 scale formed at 500"C, Aylmore et al.' reported a minimum volume fraction of connected voids equal to 0.15. While these scales often appear to be quite porous when viewed in metallographic cross section, they are so brittle that metallographic preparation is likely to exaggerate any porosity originally present. In this investigation, porosity developed during the oxidation of pure columbium and present at the high temperature was detected by oxidizing specimens in sealed evacuated capsules containing large compacts of mixed copper and CuzO powders. wooda has demonstrated that the CuzO, or (CuzO),, molecule is volatile and that oxygen is transferred by the CuzO molecule from a Cu/CuzO mixture to materials having a greater affinity for oxygen. For each molecule of CuzO that is reduced at a sink for oxygen, two atoms of copper are deposited. Quantitatively, essentially all of the oxidation carried out by a Cu-Cu20 compact results from a displacement reaction involving the CuzO molecule. When a metal which oxidizes to form a porous scale is exposed to the CuzO vapor, the CUZO molecules are reduced in the pores leaving a deposit of metallic copper to mark the site of the reduction. This technique has the rather unique advantage that any copper-coated pores found in the scale are unambiguously related to the reduction site in the growth of the scale under consideration. Pores or cracks which form in a msition*- external to the reduction site or which occur as a result of cooling or handling of the specimen will not exhibit the copper deposit. EXPERIMENTAL PROCEDURE Marker experiments were made on columbium metal, and on pellets of CbO which had been pressed and sintered. Platinum wire markers (0.001 and

Jan 1, 1968

By D. Harker, M. J. Murphy

The mechanism by which age-hardening takes .place is still not completely understood. The principal theories range from the extreme of "precipitaiion-hardening" to that of "order-hardening," with many intermediate gradations. In the hope of obtaining new data on which to base a choice among the many theories, the authors have made electron micrographs of formvar replicas taken from metallic specimens at various stages of age-hardening. The results so obtained on an alloy of 2 per cent beryllium in copper and one of 20 per cent molybdenum in iron will be described in the following pages, as well as the technique used in preparing the replicas. Preparation of Formvae. Replicas of Metallic Specimens This section is concerned with the techniques that have roved successful in preparing formvar replicas for studying the microstructure of metals with the electron microscope. Because of its simplicity and accuracy, the formvar replica1 method developed in the General Electric Research Laboratory has been used exclusively, since it is much simpler than the silica replica method of Heidenreich and Peck2 and produces as good results. The formvar method to be described requires a technique acquired only by practice, and no foolproof set of rules can be given. it is a rapid method and a replica can be obtained in less than five minutes under favorable conditions. This does not mean that perfect replicas can be produced every five minutes, but rather that one can well afford to take several strippings* in order to produce a replica of high quality. The metallographic technique required for replica work—very fine polishing and etching with very dilute solutions—is described here. It can be said, in general, that almost any surface that has been carefully prepared for a photomicrograph at 1000 or more diameters can be used to obtain a replica for the electron microscope. Preparation of Metallographic Specimens The preparation of the metallographic specimens is somewhat more exacting than that usually given to samples to be used for inspection under the light microscope. After much experimentation, it was concluded that the best method consists in polishing the metal through to the coarse cloth, then etching and repolishing on final cloth until the layer of distorted metal is removed. After this procedure has been completed, a dilute etch—to approximately the depth necessary for a micrograph at 1000 diameters—usually produces a sur-

Jan 1, 1945

By Carmine D. &apos, Lemuel Tarshis, Joel Hirschhorn, Antonio

Vapor-deposited nickel films in the thickness range 700 to 4360A were tested in uniaxial tension utilizing a microtester designed specifically for this study. Contrary to the findings of some investigators, a definite thickness-strength relationship was observed below 3000 A with a four-to sevenfold increase in strength over that of bulk nickel. The films were characterized by high elastic strains and little plasticity. On the basis of these and other reported data, it is suggested that the high strength level in metal films is related to the manner in which they are produced. Vapor deposition, owing to its severe quenching effect. is believed to promote the formation of point defects which inhibit dislocation movement. IN recent years it has been reported that metals, when in the form of thin films, exhibit extraordinarily high strengths. The data published to date have been primarily concerned with silver and gold because of the ease with which these metals can be vapor-deposited and their high resistance to surface oxidation. Previous investigations into the mechanical strength of thin films has uncovered an apparent dichotomy of view on film behavior. Beams and his co-workers have reported a definite dependence of strength on film thickness. Other workers,"-'6 however, in separate studies on the strength of poly crystalline and single-crystal films have found no such thickness-strength relationship. The study of thin-film strength is extremely difficult because of the many variables associated with film preparation, handling, and testing. Moreover, the manner of test employed by different investigators has varied quite radically, ranging from simple uniaxial-tension to biaxial-bulge testing. The work reported herein was conducted in order to determine the mechanical behavior of a structural metal when in the form of a vacuum-deposited thin film and to gain some insight into the reasons for the high strengths exhibited by metals having such a con- figuration. In this study a method of test was chosen which would yield results which are easily interpreted and lend themselves to comparison with properties of the same material in bulk form. Moreover, specimen-preparation parameters and film-handling techniques are set forth so that other investigators can properly compare their findings with ours. EXPERIMENTAL PROCEDURES A) Film Preparation. Vacuum deposition was performed in an 18 by 30 in. bell jar using a standard New York Air Brake Co. vacuum station with a 6-in. oil-diffusion pump. Before evaporation the system was pumped to a pressure of less than 2 x 10"5 torr. A shield was employed to protect the substrates from the emission of contaminants during the critical melting and outgassing of the evaporant. The source consisted of from one to six filaments (0.020 in. diam). The length of each filament was about 5 in. and was placed 6 to 8 1/2 in. from the substrate in such a manner that the substrate face was at 90 deg incidence with respect to the evaporant beam. The temperature of the source was 2000"~ during evaporation. The films were deposited onto a substrate arrangement which was composed of four basic components, that is: 1) a 3 by 1 in. glass slide; 2) a 22-mm sq micro cover glass on 1); 3) a 22 by 50 mm micro cover glass coated with collodion on 1); and 4) a stainless-steel sheet mask containing twelve rectangular openings of 1-mm and 2-mm widths and lengths of 5 mm laid over 3). Thus, test specimens of 1-mm and 2-mm widths are deposited onto a collodion substrate which precludes epitaxial effects in the specirnens. 17-le The rectangular cover glass and square cover glass were positioned in such a manner that a strip of film would be evaporated along the length and across the width of the large glass slide. This boundary of evaporated film was used to determine the film thickness by multiple-beam interferometry. The square cover glass was used for X-ray and chemical analyses. Thickness of the deposits was varied by changing the number of filaments used (one to six). The duration of evaporation was 30 sec for each filamgnt which resulted in a deposition rate of 8 to 20A per sec. Evaporations were all performed at room temperature; however, radiant heat from the source raised the substrate temperature to 40" to 60°C. All substrates were cleaned by ultrasonic agitation in a solution of spectranalyzed isopropyl alcohol. Collodion was deposited on the micro cover glass by immersion in solution of collodion in amyl acetate. B) Thickness Control and Measurement. Film

Jan 1, 1963

By S. Gstalder, J. Raynal

Consideration was given to simple tests which could be performed on rocks to give a measure of rock drillability. Various methods of breaking rocks were considered and the hardness test developed by Schreiner was selected for this study. The test involves application of an increasing load on the rock face through a flat-faced cylindrical punch until rupture occurs. Test results show that hardness is a good measure of the breaking strength of rocks. Useful relationships are shown to exist between hardness and other physical quantities such as specific disintegration, Young's modulus and sonic velocity. Specific disintegration (volume of rock broken per unit of work input) provides a possible means of comparing the effectiveness of other methods of rock breakage. The relationship between hardness and sonic velocity may be very significant for it may be possible to deduce rock drillability from sonic log data. provided that a mineralogical factor is taken into account. TO test further the results of the work, laboratory drilling tests were performed which closely simulated down-hole pressure conditions. Correlations of drilling results with rock hardness measurements were quite good. It was concluded that rock hardness, as measured in the laboratory or as deduced from sonic logs, could be used in relations for predicting rock drilling performance. INTRODUCTION Drillability of rocks cannot be defined in an absolute manner by a single quantity or measured by a single test. Resistance of rock to drilling depends to a large extent upon the means used for rock destruction. This complicates drillability classification of rocks for there may be as many classifications as there are methods of rock breakage without known functional relations between them. The objective of this work was to develop. in terms of rock destruction behavior, means of selecting the best drilling method for a given rock or the conditions for optimum output from a given drilling method. ANALYSIS OF ROCK DESTRUCTION TESTS Gauthier and Baron' have reviewed the many test methods which have been developed for determining the resistance of rocks to breakage. These include drilling tests, punch tests, scratch tests, resistance to shock, wear tests, etc. A standard drilling test might be to determine the time required to drill a standard depth (1/16 in.) in a rock using a bi-cone microbit (1 1/4-in. diameter) when a standard load (417 Ib) is applied at a standard speed of bit rotation (110 rpm). From the standpoint of similarity, the results of microbit drilling tests would seem to be most representative of the several methods suggested above. However, evaluation of drilling performance by this method is only qualitative and cannot be applied directly to actual drilling conditions. Punch tests basically measure rock hardness. Punches of various shapes and sizes, including small cones for Vickers' and Knoop's tests, the wedge for Epstein's test and the right circular cylinder for Schreiner's test, have been used. Results of these tests lead to a quantitative hardness classification which would seem to be related to the resistance of rock to bit-tooth penetration. Scratch tests are related to the resistance of rocks to abrasion such as would be encountered in drilling with diamonds. Either the width of the scratch obtained at a fixed load or the load required to give a scratch of a fixed width may be used to evaluate surface hardness of the rock. This should be related to the resistance of the rock to wear. The above tests, and probably many others. give relative measurements of the breakage or destruction characteristics of rocks. There is no direct relation between results of these tests and the drillability of rocks. Also, the tests each measure different quantities which have different dimensions and they do not permit direct comparison of numerical values. As one step in rectifying the above difficulties. it is proposed that the results of all test methods be expressed in terms of volume of rock destroyed per unit of work required; this is referred to as "specific disintegration". Test results may then be reported in a form which shows both a classification of rocks in regard to each method and a comparison of methods with regard to each rock. The disadvantage in using specific disintegration is the difficulty of measuring this quantity with accuracy. The volume of rock damage is difficult to measure. as is the true value of work input. Rock heterogeneity adds to the

Jan 1, 1967

By J. M. Woodall

GuAs crystals which have been grown in quartz boats by the horizontal Bridgman method in the pvesence of Ga20 vapov have beetz found to have carrier and donor distributions which do not correspound to those expected from simple dopant seg-vegation during directional freezing; Instead, the carrier distribution is determined by the heat-trentnzent history of the crystal, while the donor distribution, zohiclz is principally due to silicon, is fixed by the pozuth rate, the geo)tlet.ry of the crystal growth vessel, and tlze initial Ga20 pressure. WHEN semiconducting materials are made into doped crystals by the normal freezing method,&apos; they usually exhibit doping variations along the growth axis. If a) there is no dopant diffusion in the solid, b) the dopant is distributed uniformly in the melt, and c) the distribution coefficient, k, does not vary with composition, then the doping variation along the growth axis is represented by the equation: where C is the doping level in the solid at a point where a fraction g of the original liquid has frozen, and Co is the mean concentration. When the dopant is either a singly ionized shallow donor or shallow acceptor, C also represents the carrier concentration. Even though this equation accurately describes the dcping profiles of a large number of normal freeze systems, there are several special systems for which Eq. [I] does not apply. One such system is the horizontal Bridgman method for preparing oxygen-grown GaAs crystals using quartz vessels. Several workers2"* have shown that GaAs crystals grown by the horizontal Bridglnan method using quartz vessels are generally contaminated with silicon in concentrations in excess of 5 < 10lG atoms per cu cm. This contamination is ascribed to a reaction: occurring at the walls of the crystal-growth vessel which liberates silicon into the melt and Ga2O vapor. It has been shown4 that this reaction, and, hence, the silicon contamination, can be suppressed by the addition of oxygen to the crystal-growth apparatus. It is the purpose of this paper to describe a special apparatus capable of yielding single crystals of GaAs grown in the presence of oxygen and to describe both the kinetics of silicon suppression in this system and the relationship between the carrier concentration profile and the silicon concentration profile. EXPERIMENTAL-CRYSTAL GROWTH A schematic diagram of the apparatus used in the oxygen addition experiments is shown in Fig. 1. The most important features of this apparatus are: a) the use of a sand blasted quartz boat, h) a quartz rod of length 1, with a hole of cross section A, that is placed near the boat to limit the free space volume V, over the melt during the growth, and c) the temperature gradient at and near the solid-liquid interface. Sand blasting the boat is necessary to prevent wetting of the melt. The quartz rod retards the diffusion of the GazO vapor away from the melt to the colder portions of the ampoule. A crystal is prepared by first loading a 5.5-in. boat, which has been cleaned in aqua regia, with 40 g of 99.9999 pct Ga along with 1 to 8 mg of Ga203 powder. GazO3 is a convenient source of oxygen since it reacts with gallium at the melt temperature to form Ga20 vapor, the species which apparently controls the suppression of silicon contamination. The loaded boat, the quartz rod, and the 99.9999 pct As are placed in the ampoule as shown in Fig. 1. Generally, GaAs seeds were not used since most of the unseeded growths resulted in monocrys-tals. The ampoule is evacuated to 10-5 Torr and sealed off. The GaAs melt is synthesized by placing the ampoule into a two-zone horizontal Bridgman furnace. The two zones are separated by several sandwiched layers of -in. Fibre-Fax board drilled with holes slightly larger than the OD of the ampoule. This causes a very large temperature gradient between the two zones, which is necessary for single-crystal growth. The two-zone furnace is mounted on a stand fitted with a roller bearing which allows uniform motion of the furnace in a horizontal direction. A uniform velocity of the stand is achieved by the use of a windlass device which winds up a wire attached to the stand. Movement of the solid-liquid interface is accomplished by fixing the position of the ampoule and moving the stand. Growth rates investigated in this experiment were between 0.4 and 1.2 in. per hr. The composition of the melt is fixed by maintaining an arsenic reservoir at 618°C. The stand is moved away

Jan 1, 1968

By E. A. Gulbransen, J. W. Hickman

IN a previous paper1 the authors have investigated the structure of the oxide films formed on most of the metals that make up the alloys of this study. The metals were studied in order to provide basic information on the structures, both physical and chemical, of the oxide films and to determine how these structures are effected by the temperature, time of oxidation, and surface preparation. It was felt that an understanding of the physical and chemical structure as well as the stability of the oxide film might furnish clues as to the nature of the reaction process and the protective quality of the film. The oxidation of the metals was studied over the temperature range 300° to 700°C. except for copper, where the range selected was 100° to 500°C. The results of these studies were presented in graphical form as existence diagram, of the oxides on a time-temperature scale. For some of the metals the existence diagrams were simple and showed few chemical transitions, but there were numerous cases where the physical state of the oxide surface was a function of time and temperature. In general the physical state of the oxide surface changed with increasing temperature so as to increase the sharpness of the diffraction patterns and to cause orientation effects to be more pronounced. Deviations in lattice parameters from X-ray values were noted. In general these deviations were of positive nature and may be due to solid solution of the metal in the oxide lattice. This effect might be expected in thin oxide films. In a study of the oxidation of alloys containing two or more metals, there may arise the complicating factor of identification of the oxides formed. A thorough understanding of the oxides formed on the pure metals, therefore, was, essential before investigation of the oxidation of alloys. In this paper it is our purpose to present a study of the following problems: I The existence diagrams of various alloys. [2.] The effect of the structure of the [ying] metal on the existence diagram of Iron. 3. The effect of the percentage of chromium on the oxides formed on Fe-Cr alloys. 4. The relationships, if any, between the oxides formed and the protective quality of the oxides. The following alloys are included in this study: alloys of iron with body- centered cubic, face-centered cubic and other metals, 13 Cr-Fe, 18-8 stainless steel, K42B1 Nichrome V, Hipernik, Inconel, Stellite " 21," Refractaloy, Kovar, mild steel, a series of Cr-Fe alloys and a series of Co-Fe alloys. Since many of the commercial alloys in this list contain more than two metals, various complicating factors in the identification of the oxides formed may arise.

Jan 1, 1946

By Donald D. Smythe

Tars paper describes briefly the topography and geology of the region where the mica-bearing pegmatites are found and discusses prospecting, the quality of the mica, its preparation, and evaluation of the deposits. Muscovite mica occurs in a number of widely separated localities in Brazil, but production has come largely from deposits in the southeastern and eastern part of the State of Minas Gerais (Fig. I). There the deposits form a discontinuous zone, which starts at a point 90 km. north of the city of Rio de Janeiro and extends north for some 500 km., roughly parallel to the coast. A maximum width of 180 km. is reached along the Rio Doce. To the west in Minas Gerais, and extending east into the states of Espirito Santo and Rio de Janeiro, the mica zone proper is fringed by areas in which there are scattered occurrences of mica-bearing pegmatites. A few of these outlying deposits have produced commercial mica, but most of them are unimportant. To the southwest, in the State of São Paulo, there are a number of mines, which at one time produced a very considerable amount of sheet mica, largely as a by-product of kaolin mining. These deposits, and, a few others lying between them and the main productive areas to the northeast, appear to be the southwestern continuation of the strong Minas Gerais mica zone. In the vicinity of Conquista, just north of the Minas Gerais boundary in the State of Bahia, and still farther north, near Jacobina, there are several known mica deposits. Their location indicates that they may be the northern continuation of the main mica zone. The major part of Brazilian mica production has come from four areas within the mica zone proper; from north to south, Governador Valadares, Raul Soares, Espera Feliz, and Muriaé. The first is 190 km. from north to south and reaches a maximum width of 180 km. The Raul Soares area extends 135 km. from northeast to southwest, and in places is 80 km. wide. The Espera Feliz area is 100 km. from north to south, and reaches a width of 35 km. The Muriaé area extends 150 km. from northeast to southwest and its width reaches 40 kilometers. Between the known productive areas, and in the areas directly to the southwest and to the north of them, little mica has been produced. These gaps, as well as certain irregularities in the outline of the mica zone itself, are to be ascribed either to lack of prospecting or to conditions preventing the discovery of mica, rather than to its nonexistence. Elsewhere in Brazil mica has been reported from eastern Goiaz, Ceará, Pernambuco, Rio Grande do Sul, Matto

Jan 1, 1946

By George Norman

A NUMBER of methods have been developed for the determination of the dust concentration in air, some of which have been reported as very efficient and for research may be more satisfactory than the method about to be described. In practical mine use, however, the accurate research equipment is unwieldy and requires a high degree of technical skill to manipulate it. Also, it gives less general practical information to the operator in the same length of time than the method described here. Moreover, it is doubtful whether at the present stage of affairs the results obtained from the precise methods have any more practical significance than those obtained with simpler and more portable appara-tus, which can rapidly give a sufficiently reliable indication of the rela-tive dust hazard.

Jan 1, 1937

By William Sellers

tested without knowing anything of their chemical composition. I had these pieces separately placed upon 10-inch bearings under a 7-gross ton lianlrner, a piece of 2½-inch round iron laid upon them as a fuller, and the hammer allotved to fall from 20 inches above the fuller, which, according to Haswell, gave a ldow of 67.75 gross tons. The pieces were then turned orcr, the fuller placed upon the convex surface, and the harnnler allowed to fall from 13 inches above the fuller, giving a blow of 58.46 gross tons. You will see that the rails do aot show ally bigrls of ruptnre, and their color at the points of torture prove them to have been absolutely cold when the test was made. I thirk these rails ought to be reasonably safe in the track. As you see by this piece of the head of one of these rails, I had it plarred, and then some teeth cut in it by a cold clrisel, and one-half of them pounded down with a hammer. The teeth of my rack did not break off. The analyses of these rails substquently made are: I. 11. Carbon,... 0.110 0.880 Silicon,..0.050 0.058 Phosphorus ,..0.086 0.082 Manganese,.. 0.042 0 840 In conclusion, I will say that Dr. Dudley&apos;s paper as a contribu tion to our knowledge of steel rails is valuable and interesting, but I protest against his conclusions king reoeived as manufacturing or comtnercial axioms. From its being presented in the form-of a report to the leading railroad of the country from one of its trusted officers, as well as from the tone of the concluding deductions, it is liable to be so received by railroad men. If any railroad com pany desires rails made under either of Dr. Dudley&apos;s formulas, and are willing to pay a price large enough to cover the loss in making them, dl and good; but so long as the rail makers are compelled to gwrrantee the wear of their rails for a given number of years, justice reqnires that. the composition of the steel from which these rails are made should be left to them. WILLIAM SELLERS, PHILADELPHIA: The very interesting paper upon the wear of steel rails that has just been read preseak the record of a series of investigations that are extreniely valuable, and the deduction that bas been drawn from the results noted seems to be unavoidable; the tests, however, to which it is proposed steel rails shall be subjected hereafter, with a view to determine their quality, sllould

Jan 1, 1881

By Frank M. Monroe, James R. Cost

The solubility of nitrogen in vanadium is determined from 275" to 575°C by measuring the height of the nitrogen internal friction peak of equilibrated V-N alloys. The proportionality constant at 275°C between the internal friction peak height (Q- 1) and the atom percent nitrogen in solution is found to be 0.095 per at. pct for nitrogen concentrations up to 0.8 at. pct. The heat of solution of the nitride in vanadium is 5500 cal per mole. The solubility of nitrogen in the Group V metals is discussed. LITTLE work has been performed on the vanadium-nitrogen terminal solid solution. Hahn1 found the solubility for nitrogen to be very small and reported the existence of a hexagonal phase of composition near that of V2N at the solubility limit. Rostoker and Yamarnoto2 reported the solubility to be at least 3.5 at. pct at the melting point and to be less than this value at 900°C. In addition, they reported from X-ray diffraction studies that nitrogen in solution produces tetragonality in the vanadium lattice. An X-ray study by Schonberg3 has confirmed the results of Hahn but indicated that the tetragonality observed by Rostoker and Yamamoto was due to the presence of oxygen in their specimens. Beatty4 has performed lattice parameter and hardness measurements on terminal solid solutions and found the upper limit of the solubility to be at least 0.66 at. pct N. No measurements have been made of the pressure-temperature-composition relationships (P-T-X) for the terminal solid solution. As a part of a research program on gas-metal equilibrium, an attempt was made to study the P-T-X relationships in the V-N system using both the internal friction and the gas equilibration methods which have been successful with the Nb(Cb)-N and Ta-N systems (see Ref. 5 for a review of this work). Extensive investigation, using the gas equilibration methods, showed this method not to be applicable with vanadium This was presumably due to the gettering action of vanadium sublimed on the walls of the Sieverts apparatus. Thus, the nitrogen pressure relationships with temperature and composition were not obtained. The internal friction methods were, however, found to be applicable, and the temperature-composition relationships are reported in this paper and compared with similar results for the Nb-N6 and Ta-N7 systems. The existence of a Snoek internal friction peak due to nitrogen in solution in vanadium has been clearly demonstrated. 8-10 Powers and Doyle found the peak to be at approximately 275°C for frequencies near 1 cps.8 In a subsequent paper10 they reported the proportionality constant at 275°C between the internal friction peak height (Q-1) and the concentration of ni- trogen in solution (in atom percent) as 0.06 per at. pct. The studies of Stanley and wert9 indicated qualitatively that the height of the Snoek peak decreased with aging at the peak temperature and thus suggested that internal friction methods were suitable for study of the solubility. EXPERIMENTAL METHOD The vanadium for this investigation was of particularly high purity. It was obtained from the Ames Laboratory of the U.S. Atomic Energy Commission, Ames, Iowa in the form of a 1/2-in. diam, three pass zone-refined ingot. The electrical resistivity ratio (p300ºk/p4ºk) was 160. The initial composition was determined as follows: Carbon 200 ppm Oxygen 150 ppm Chromium <50 pprn Iron 125 ppm Silicon <50 ppm Other metallic 100 pprn The initial vanadium ingot was fabricated to 30-mil wire by swaging and wire drawing without the need of intermediate annealing. Lengths of this wire were then further purified (particularly for oxygen) by outgassing at 10-6 torr at 1400°C for 4 hr. The outgassing treatment resulted in specimens with a bamboo grain structure and a lustrous appearance. Desired amounts of nitrogen were added to the outgassed wires in a Sieverts apparatus in which known amounts of nitrogen were equilibrated with the wire at 1300°C. Nitrogen concentrations were produced in the desired range from less than 1 to 10 at. pct N. Monitoring of the partial pressure of nitrogen in the Sieverts apparatus indicated that at 1300°C equilibrium between the nitrogen gas and the vanadium was obtained within 10 min. Relatively rapid cooling from the nitrogen addition temperature was obtained simply by turning off the specimen heating current and cooling to room temperature in the partial pressure of nitrogen. Internal friction measurements of wire specimens were made under forepump vacuum in a torsional pendulum at frequencies near 1 cps. The torsional pendulum was of low thermal inertia and was designed so that specimens could be heated both by a conventional tube furnace and by the joule heating of a separate current through the wire specimen." Use of a static atmosphere of helium gas as a quenching medium made it possible to cut the specimen current, rapidly cool the specimen to the measurement temperature, and make a measurement of the internal friction in less than 1 min. Because of the large solubility of vanadium for nitrogen, the internal friction peak heights were in some cases greater than Q-1 = 0.1. This high damping resulted in an estimated relative uncertainty in the damping measurements of approximately 10 pct. X-ray analyses made to identify the precipitated ni-

Jan 1, 1970

By Strathmore R. B. Cooke, Iwao Iwasaki, C. S. Chang

The effects of aeration on an aqueous suspension of pyrrhotite were studied and their results correlated with flotation tests using xanthates as collectors. The effects of copper activation and of pH variation were determined and possible mechanisms postulated. PYRRHOTITE has long been considered a gangue mineral to be eliminated as tailing in the treatment of various sulphide ores. However, in recent years the world-wide lack of sulphur resources has called attention to this mineral as a potential source of both sulphur and iron. Its importance as an economic mineral, however, has not been particularly emphasized. For this reason very little is known about its response to flotation, except that it can be depressed easily in alkaline circuit, by long aeration,1,2 addition of oxidizing agents,3 or by starch.&apos; The object of this work was to study the floatabil-ity of pyrrhotite. This includes the effect of oxidation by aeration, of copper activation, and of change in pH. Preparation of the Pyrrhotite Sample: It was desirable that the highest grade of pyrrhotite obtainable be used for this experiment, since the presence of other minerals could affect the surface properties.5 However, no pyrrhotite was available as crystals, and massive deposits of hydrothermal origin commonly contain considerable amounts of chalcopyrite. Pyrrhotite concentrate was, therefore, prepared from a sulphide deposit occurring near Aitkin, Minn. The deposit is of pyrometamorphic nature consistirlg mainly of pyrrhotite and pyrite with graphite, silicates, and carbonates as gangue. The ore, already crushed through 3 mesh when received, was screened at 65 mesh and the undersize discarded. The oversize was crushed through rolls, and then stage-ground dry in an Abbe porcelain mill, the —65 mesh portion being screened out after every 15 min of grinding until all the material passed through this size. The ground product was then concentrated with a drum-type dry magnetic separator. The rougher concentrate was cleaned twice and then demagnetized. The final product was split in a Jones splitter and stored in air-tight bottles. Microscopic examination of the concentrate showed that it was relatively clean and free of pyrite, locked particles, and gangue. By means of the krypton gas adsorption method," the specific surface was determined to be 3000 cm2 per g. The chemical and screen analyses of the final concentrate are given in Tables I and II respectively. It is a well-recognized fact that the oxidation of some sulphide ores during stockpiling, grinding, and conditioning affects their flotation behavior. The problem of oxidation may become serious in the case of pyrrhotite, since this is known to be more easily oxidized than many other sulphides. To ascertain the extent of oxidation, an experiment was carried out by aerating an aqueous suspension of pyrrhotite with air, oxygen, and nitrogen as follows. A 300-g sample of pyrrhotite in 2700 ml of water was agitated and simultaneously aerated in a Fager-gren-type laboratory flotation machine. A Precision wet test meter was connected to the air inlet valve, the flow rate of the gas being kept constant at 0.3 cu ft per min throughout the experiment. Samples of approximately 30 ml each were taken from the cell at 0, 4, 10, 20, 35, 60, and 90 min. After the pH was taken, each sample was filtered and the filtrate was analyzed for total iron and sulphur. The iron was determined colorimetrically by the thioglycolate method using a green filter.&apos; The filtrate was oxidized with bromine to convert all of the soluble sulphur compounds into sulphate and this was determined with a Parr turbidimeter." When aeration tests were made in alkaline circuit, calcium hydroxide or sodium hydroxide was added at regular intervals to maintain a constant pH. A similar procedure was followed in an experiment to determine the abstraction of copper. ion by pyrrhotite. In this case various quantities of cupric chloride were added. The filtrate from each sample taken was analyzed for copper, total iron, and sulphur. The carbamate method with a green filter was used for the copper analysis,&apos; since this method could tolerate a considerable amount of iron in the solution. A pneumatic cell, made from a 350-ml fritted glass Buechner funnel, was used for this experiment. The detail of the assemblage has been described elsewhere." In the present work a stainless steel baffle was inserted in the cell. This baffle overcame the tendency for the coarse pyrrhotite particles to be swirled around the wall of the cell and thus fail to collect in the froth. A 50-g sample of pyrrhotite was added to the cell which contained 260 ml of water. When pretreat-ment of the sample was desired, reagents, such as activator and pH regulator, were then added and the pulp was conditioned for a specified conditioning time. Prior to the addition of the collector approximately 15 ml of the solution were removed for pH measurement and for iron and sulphur analyses. Copper when used as activator was also determined. Collector and frother were then added and the pulp was conditioned for an additional 2 min. Air was admitted to the cell and the froth removed. The separation required from 4 to 6 min, depending on the characteristics of the froth. The float and non-float products were filtered, dried, weighed, and assayed for iron.

Jan 1, 1955

By R. A. Meussner, C. T. Fujii

Chromium solution in wustite depresses the oxygen activity in a nonideal manner and expands the lattice slightly. Gravimetric measurements of the equilibrium compositions of wustite containing 0.00 to 1.38 wt pct Cr define the oxygen potential (CO2-CO atm) and the limits of the phase field at 1000°C. These data extrapolate to a maximum solubility of 2 wt pct Cr. The lattice parameter data, room-temperature measurements of quenched samples, differ significantly from those in the literature. Both pure and chromium wus-tites contract at uniform and equal rates as the oxygen content (metal deficit) increases. The a. US metal deficit relationships are straight lines showing none of the curvature previously reported. At constant metal deficit, the a. expands by 0.002? on alloying with 0.4 to 0.5 wt pct Cr but is insensitive to further chromium additions: a small expansion rather than a marked contraction. These results require a modification of the accepted alloying mechanism. IN the high-temperature oxidation of Fe-Cr alloys in Ha-H,and CO2-CO atmospheres the vapor transfer of oxygen from the continuous wustite outer scale to the porous inner scale/alloy interface sustains the high oxidation rates.1"3 The driving force for this transport is the difference in the oxygen activity of the outer wustite and that at the inner scale/alloy interface. In pure CO2, as well as in CO2-CO atmospheres, carburization of the alloy accompanies this oxidation. Current efforts to evaluate the parameters controlling this carburization have shown that the process is not simple; i.e., the carbon concentration in the alloy initially increases rapidly, reaches a maximum, and then decreases slowly as the oxidation time is extended. This is the same pattern reported by McCoy for the more complex oxidation-carburization of stainless steels and an Fe-Cr alloy in CO2 at lower temperatures.4 These changes in the carburization process occur while the overall oxidation rate and the lattice parameters of the scale layers remain constant. If this invariance of the lattice parameter is assumed to indicate a constant scale composition and thus a constant oxygen potential, the carburization results are not easily explained. Electron microprobe traces across the thickness of these outer scales, however, have revealed distinct chromium gradients penetrating 10 to 50 µ from the inner surface where the chromium concentrations were estimated at a few tenths percent. The variation of the chromium cmcentration on the inner surface of the scale, and the resulting change of the oxygen activity, during the oxidation process is considered to be important in defining the carburization process. Thus, to gain an understanding of the complex oxidation-carburization proc- ess, it was necessary to measure the properties of wustite containing known amounts of chromium (chromium wustite). Although the general features of the Fe-Cr-0 equilibrium diagram between 900° and 1300°C have been fairly well established by Richards and white: Wood-house and White,6 Seybolt,7 and Katsura and Muan,8 there have been no detailed studies of the limits of the chromium wustite phase field or the properties of these alloyed wustites. The recent results of a limited study of chromium wustite by Levin and wagner9 indicate that more than 0.67 wt pct Cr is soluble in wustite above 850°C and that this alloying is accompanied by a substantial lattice contraction. This change in the lattice parameter was not evident in the X-ray diffraction patterns of wustite layers from the oxidation experiments;1,3 the lines were sharp even though a chromium gradient existed in the scale. The present paper describes gravimetric equilibrium experiments which delineate the boundaries of the chromium wustite single-phase field at 1000°C and define the changes in the oxygen activity and the lattice parameter of wustite as functions of chromium and oxygen contents. The lattice parameter data of chromium wustite obtained from these equilibrium and special quenching experiments differ considerably from those reported.9 Those for pure wustite show significant differences from the widely accepted data of Jette and Foote.10 Since the causes of these differences are not easily assignable, and since the literature contains many sets of data on wustite which if not in conflict are at best not in harmony, the experimental procedures are discussed in the present paper. EXPERIMENTAL Oxide Preparation. The specimens used in these studies were porous pellets compacted from high-purity (Fe,Cr)2O3 or Fe2O3 powders. These powders were prepared from electrolytic chromium (99.8 pct purity) and electrolytic iron purified by consumable-electrode, vacuum arc-melting processing (299.9 pct purity).11 The oxides were produced by standard analytical procedures: solution of the metals in acids (HC1, then HNO3 added), coprecipitation of the hydroxides (NHaOH), and filtering and washing these precipitates. Initial dehydration of the coprecipitated hydroxides was done in a porcelain evaporating dish heated by a Meker-type burner, final dehydration by firing in a recrystallized alumina crucible at 1000" to 1050°C for 20 hr in an electrically heated furnace. Spectrographic analysis detected the following impurities: silicon, 0.01 pct or less; aluminum, 0.001 pct to trace; manganese and copper, 0.0001 pct to none. Each of these levels is at least one order of magnitude lower than in commercially available CP grade ferric and chromic oxides. Fluorescence analy-

Jan 1, 1969

By Arthur F. L. Bell

Prior to 1908 the oil production in the State of California had been almost entirely a heavy fuel oil, with a high flash point, but changed within a short period to a large percentage of refining oil with a low flash, by reason of the heavy production of light oil coming in from the Santa Maria field, the Midway field, and the increased production of the Fullerton field. This is clearly shown in the following tabulation of California&apos;s pro- The bringing in of these high percentages of light oil with their dangerous low flash and the increasing demand for the refined products necessitated the devising of some cheap and efficient means of quickly separating the lighter elements either in the field or at the main distributing points; also it became necessary to remove the excessive percentage of water which many of the light oils carried in emulsion. Union Oil Co. Port Harford Plant Probably the first important attempt to top light oil in California by other means than the ordinary stills was tried about 1908 by the Union Oil Co., at its plant at Port Harford, San Luis Obispo County, with Santa Maria oils. The process was the invention of Hubert G. Burroughs who afterward obtained a patent for the process, No. 998,837, dated July 25, 1911. The apparatus used consisted of a series of 12-in. pipes mounted in units of three pipes, one above the other, the crude oil being admitted to the upper pipe and filling it about two-thirds of its

Jan 1, 1916

By Robert L. Slobod

In much of the work reported in the literature on long cores. true connate water value, probably have not been obtained because of insufficient flow of 011 to attain equilibrium. A -.satisfactory method for establishing connate water in long cores has been developed in which oil flow is maintained until no additiona1 water is displaced. INTRODUCTION Long cores have been used by sev-erals investigators in an effort to evaluate the efficiency of oil recovery for various producing schemes. The effects of many variables such as rate of displacement. pressure drop, volume of displacing medium, gas-oil ratio, inter-facial tension, and others have been investigated, and the merits of gas drive have been compared with water drive. In the older experiments no connate water was used. but in the more recent stndies the philosophy of the experiment calls for a core containing oil and connate water (irreducible water) as the starting point of the experiment. The method generally used to establish this condition in long cores involves dynamic&apos; displacement wherein one or more phases are forced through the core. flow being maintained at a constant rate or at a constant pressure until a steady state is reached wherein there is no change of saturation with time. It is one purpose of this paper to point out that in much of the work reported in the literature true connate water values probably have not been obtained. The reason for this failure is pointed out. and a method for obtaining more reliable connate water values on long cores is presented. It is impossible at this time to completely evaluate the effect on the conclusions in the earlier papers resulting from the failure to obtain true connate water in the long cores, but some data are presented which indicate that serious errors may he present in many cases. MATERIALS AND APPARATUS Cores cut front outcrop sandstones (Strawn. Torpedo, and Elgin sandstones) with permeabilities of the order of 300 md were used. The major experiments were made with a core 18-in. long and 2-in. in diameter. Cores of the same diameter but only 12-in. long were used in a few tests? and in some work a core I-in. in diameter and 11-in. long was used. These materials were all somewhat bentonitic. &apos;To reduce the effect of such constituents, one of the cores (Torpedo No. 10) on which the most work was performed was acid extracted at the start of the experiment. Brine containing 50,000 ppm chloride and naphtha (Stoddard&apos;s Solvent) were used as the water and oil phases, respectively. The core was mounted in a rubber sleeve which forms the inner lining of a brass cylinder. In this arrangement2 the rubber sleeve is forced against the core by applying pressure to water in the annular space between the rubber sleeve and the brass cylinder wall. The core is therefore sealed in rubber so that all fluids introduced at the input end of the core flow through the core. With this equipment the core may be easily removed for inspection and analysis. Also, other cores may be introduced for study with no extra time for preparation such as is required when plastic mounting is used. When pressure or conductivity measurements are desired at intermediate points along tile length of the core, the brass cylinder comprising the outer jacket of the core holder is cut into section, of the desired length. Each section is then made up as an individual unit with its own rubber sleeve (see Fig. 1). The individual units are then butted up against a ring of plastic or other insulating material which carries an electrical contact for resistivity measurements and an opening which can be used for the measurements of fluid pressures. The individual units are forced tightly against the plastic ring separators and held in place with several tie rods. Inlet and outlet end butts of the same diameter as the core and several inches in length are provided to control the introduction and withdrawal of fluids and to complete the arrangement for sealing the core within the rubber sleeve. Fluid flow is maintained either by applying pressure to the liquid confined in a reservoir or by the use of a gear pump. The latter is preferable where continuous flow at a moderate rate over a long time interval is desired since a small volume of liquid can be readily recirculated using filters to prevent plugging of the core. EXPERIMENTAL The oven-dried core is weighed and is then completely saturated with brine

Jan 1, 1950

By Reuel A. Cochrane, Harry H. Angst

The successful exploitation by opencut methods of the low-grade porphyry copper deposits is due to the economical handling of large tonnages. Large tonnages are possible only if the rock material is broken so that the large power shovels can operate with minimum delays. This is particularly true at the New Cornelia mine, where the dense, hard, tough rock material creates problems not encountered in most of the porphyry copper mines. The introduction of churn drills at the New Cornelia for primary drilling, in 1936, necessitated a complete change in the methods of breaking ground as formerly air drills had been used. The blasting operations are of particular interest because of the handling of great quantities of high explosives in safely and efficiently fragmenting the hard rock material. Rock Formations At the New Cornelia mine the rocks are quartz monzonite with a diorite border facies intruding a rhyolitic series. Overlying these formations is a fanglomerate formation composed of boulders of monzonite, diorite, rhyolite, and other types of rock of unknown derivation. (The word "fanglomerate" is used in this paper in referring to the local conglomerate type of rock formations.) The ore body is approximately 4800 ft. long and 2800 ft. wide, and is of the disseminated type. Mineralization occurs principally in the quartz monzonite and to some extent in the adjacent diorite and rhyolite. The principal ore minerals are chalcopyrite, bornite, and a small amount of chalcocite. Over a considerable area the quartz monzonite is extremely hard and siliceous in character, owing to pegmatitic zones of alteration. The hardness of the ground depends on the intensity of the silicification. In a small area in the pit, the monzonite contains an abundance of pyrite accompanied by sericitization and is soft and easily fragmented. This is true also in the remaining oxidized portion of the ore body. The diorite and rhyolite formations, like the monzonite, vary from extremely hard to very soft material, but on the whole are easier to fragment than the monzonite. Jointing is prevalent in all the rock formations and plays an important role in the blasting efficiencies. In the fanglomerate formation, numerous well-defined joints, widely spaced, tend to make the ground blocky when blasted. This is a deterrent to good fragmentation. In the other rocks the joints are more numerous and are closely spaced, except in localized areas where the formations are extremely hard. These descriptions indicate that the lowest blasting efficiency will be obtained in the harder formations, from which the major portion of the mine production is obtained; namely, the monzonite and rhyolite. All rock formations mined at the New Cornelia pit are so hard that excavation

Jan 1, 1943

By Arthur Phillips

THE normal method of preparing metallic alloys for commercial use involves the preparation of a melt containing the given components in the chosen proportions and allowing the homogeneous liquid mass to solidify in a mold of the desired form. The solidification is frequently accompanied by a segregation of the alloying elements in different parts of the casting. When the segregation is occasioned primarily by marked differences in density of the solid and liquid phases, it is termed "gravity" segregation. When the segregation conforms to a. selective freezing in harmony with the teachings of the equilibrium diagram of the alloy system-i.e., the lower melting phases are concentrated in the regions of the casting last to freeze-it is often referred to as " normal" segrega-tion. However, in many cases the lower-melting part of the system is concentrated in the parts of the casting first to freeze and the result in this case is termed "inverse" segregation. To complete the. terminology of the subject, normal segregation in a single phase is usually called "coring" and the word will be used in that sense in this paper. Inverse segregation, particularly when the liquid phase is exuded or sweated out on the surface of the casting, is sometimes called "location." Unfortunately, some ambiguity has arisen from the use of this term and it is perhaps advisable to confine its use to the dictionary definition; namely, "The separation of two phases by heat sufficient to melt one but not the other." The gravity and normal types of segregation are both well understood and to some extent are controllable by taking advantage of the most favorable cooling rate for a given casting condition. Inverse segregation has received considerable attention from several investigators- but none of the theories offered seem to account in a convincing way for the many examples of this type. The observations made in the present work on segregation in single crystals, and in some other castings, tend to support one theory of the mechanism of inverse segregation and definitely to

Jan 1, 1937

By Henry M. Howe

Jan 1, 1909

By Martial P. Corriveau

Almost everyone agrees that coal and oil shale are the only fossil fuel resources in which the United States is self-sufficient. Of the two, only coal has a technology sufficiently developed to be of intermediate term benefit. Since it takes at least 20 years to bring advanced technology into practice, it seems logical that the major focus on energy developments should be aimed at coal. Meanwhile, we need to trade-off between actions to meet our immediate needs and the various political regulations and social demands that are disrupting the coal industry and the industries dependent upon it. The largest single user of coal is the electric power generation industry. Over 300 million tons of coal are presently being consumed each year. In view of the 5-to 7-years lead time to bring in a base-load fossil-fuel fired generating station, our requirements for double this tonnage in 1980 are already well forecast; that is, if the coal companies are allowed to mine and the utilities are allowed to burn the coal.

Jan 2, 1974