Search Documents

By T. P. Meloy

The behavior of slime-sized particles in a flotation cell is neither well documented nor well understood. In general, slimes (or 'fines' as they will be alternatively called in this chapter) have been either ignored, eliminated, or treated empirically. Recently, however, some good experimental and theoretical work has been done that leads qualitatively to a clearer understanding of the problems involved. Fines are small particles that, owing to their smallness, behave differently from larger particles of the same material. The smaller the particle, the larger is its surface-to-mass ratio. The difference in the surface-to-mass ratio for a micron-sized particle and a centimeter-sized particle is 10,000 to 1. For our purposes we shall arbitrarily define any particle less than 10 µ 10-3 cm) as being a fine. This is generally considered the upper limit of colloidal-sized particles. Recently, the field of colloidal chemistry has successfully used the concept of the double layer to explain dispersion and flocculation of fine particles in a static system. Flotation, however, is a dynamic system due both to the turbulence of the liquid and to the coursing of the bubbles through the cell. Further more, a flotation system is a heterogeneous system in which there are a number of different types of particles which interact with one another. A further difficulty is that no two flotation systems are the same for minute quantities of a variety of common chemicals will alter the behavior of the system. These reasons make reproducible experimental results that can ex- plain fine-particle behavior difficult to obtain. In spite of these experimental difficulties, millions of tons of ore containing a large amount of fines are successfully floated every year. For example, at the Morning mill of American Smelting and Refining Co., a galena concentrate that was 42% -6 µ and a sphalerite concentrate that was 33% -9 µ were floated leaving a tailing that was 27% - 9 µ.l Ores that contain fines can generally be divided into two classes. In the first are those in which the valuable mineral tends to slime, such as galena and hematite. In the other class, one or more of the gangue minerals forms the slime; a typical example is barite. Though the problems due to the presence of fines are often the same in handling the two classes of ore, the method of handling them is different because of economic considerations. Nonmetallic mineral flotation is particularly affected by slimes, by either slime-coating effects or excessive reagent consumption. Though a given gangue mineral may not float under the conditions prevailing in the flotation cell, it may still be able to adsorb the collector. I£ it also slimes, a significant

Jan 1, 1962

By F. Keller, J. D. Edwards

The anodic treatment of aluminum presents problems of scientific as well as of commercial interest.l-3 Of particular interest is the fact that, during the anodic oxidation process, the oxide continues to form at the metal-oxide interface under any oxide previously formed. This has led to speculation as to the mechanism involved in the formation of the relatively thick oxide coatings that are used commercially for decorative or protective purposes. Furthermore, the ability of certain types of oxide coatings to adsorb dyes and other substances has stimulated research to determine the actual structure of these adsorptive coatings. It has been found that anodic oxide coatings on aluminum are composed essentially of aluminum oxide. They are formed by the action of oxygen ions penetrating to the metal surface during the electrolytic oxidation treatment. These coatings can be formed in a number of different electrolytes, as for example, those which contain sulphuric acid, chromic acid, oxalic acid, or boric acid. These are the commonest and most useful electrolytes employed commercially. Except for certain specific conditions of formation, the coatings in general have been found to be amorphous alumina, as far as can be determined by X-ray or electron-diffraction methods. Anodic oxidation processes can be arranged in three rather general classes if they are grouped in relation to the solvent action of the electrolyte on the coating.4 In the first class, the electrolyte has little or no solvent action on the coating that is formed. In general, coatings produced under such circumstances are nonporous and non-adsorptive. In the second class, the electrolyte exerts an appreciable solvent action on the coating. These coatings are porous and adsorptive. Finally, for the third class, the electrolyte tends to dissolve the coating about as rapidly as it is formed. This action produces electrolytic brightening or anodic polishing of the aluminum surface and at most leaves only a very thin film of oxide. The nonporous and nonadsorptive type of oxide film is represented by the coatings that are formed when solutions of boric acid are employed as the electrolyte. It is especially significant that these impervious films are formed in electrolytes that exert little or no solvent action on the coating. Where a boric acid electrolyte is used, the coating tends to form rapidly, with the result that the flow of current is soon reduced to substantially zero. This indicates that the growth of the coating has stopped. As a rule, the thickness of the coating is roughly proportional to the voltage employed for formation and the coatings of this type are exceedingly thin. In an electrolyte of this type, the coating has a high resistance when the aluminum is made anode; consequently, any current that may flow (leakage current) is very

Jan 1, 1944

By F. Keller, J. D. Edwards

The anodic treatment of aluminum presents problems of scientific as well as of commercial interest.l-3 Of particular interest is the fact that, during the anodic oxidation process, the oxide continues to form at the metal-oxide interface under any oxide previously formed. This has led to speculation as to the mechanism involved in the formation of the relatively thick oxide coatings that are used commercially for decorative or protective purposes. Furthermore, the ability of certain types of oxide coatings to adsorb dyes and other substances has stimulated research to determine the actual structure of these adsorptive coatings. It has been found that anodic oxide coatings on aluminum are composed essentially of aluminum oxide. They are formed by the action of oxygen ions penetrating to the metal surface during the electrolytic oxidation treatment. These coatings can be formed in a number of different electrolytes, as for example, those which contain sulphuric acid, chromic acid, oxalic acid, or boric acid. These are the commonest and most useful electrolytes employed commercially. Except for certain specific conditions of formation, the coatings in general have been found to be amorphous alumina, as far as can be determined by X-ray or electron-diffraction methods. Anodic oxidation processes can be arranged in three rather general classes if they are grouped in relation to the solvent action of the electrolyte on the coating.4 In the first class, the electrolyte has little or no solvent action on the coating that is formed. In general, coatings produced under such circumstances are nonporous and non-adsorptive. In the second class, the electrolyte exerts an appreciable solvent action on the coating. These coatings are porous and adsorptive. Finally, for the third class, the electrolyte tends to dissolve the coating about as rapidly as it is formed. This action produces electrolytic brightening or anodic polishing of the aluminum surface and at most leaves only a very thin film of oxide. The nonporous and nonadsorptive type of oxide film is represented by the coatings that are formed when solutions of boric acid are employed as the electrolyte. It is especially significant that these impervious films are formed in electrolytes that exert little or no solvent action on the coating. Where a boric acid electrolyte is used, the coating tends to form rapidly, with the result that the flow of current is soon reduced to substantially zero. This indicates that the growth of the coating has stopped. As a rule, the thickness of the coating is roughly proportional to the voltage employed for formation and the coatings of this type are exceedingly thin. In an electrolyte of this type, the coating has a high resistance when the aluminum is made anode; consequently, any current that may flow (leakage current) is very

Jan 1, 1944

By F. Keller, J. D. Edwards

THE anodic treatment of aluminum presents problems of scientific as well as of commercial interest.1-3 Of particular interest is the fact that, during the anodic oxidation process, the oxide continues to form at the metal-oxide interface under any oxide previously formed. This has led to speculation as to the mechanism involved in the formation of the relatively thick oxide coatings that are used commercially for decorative or protective purposes. Furthermore, the ability of certain types of oxide coatings to adsorb dyes and other substances has stimulated research to determine the actual structure of these adsorptive coatings. It has been found that anodic oxide coatings on aluminum are composed essentially of aluminum oxide. They are formed by the action of oxygen ions penetrating to the metal surface during the electrolytic oxidation treatment. These coatings can be formed in a number of different electrolytes, as for example, those which contain sulphuric acid, chromic acid, oxalic acid, or boric acid. These are the commonest and most useful electrolytes employed commercially. Except for certain specific conditions of formation, the coatings in general have been found to be amorphous alumina, as far as can be determined by X-ray or electron-diffraction methods. Anodic oxidation processes can be arranged in three rather general classes if they are grouped in relation to the solvent action of the electrolyte on the coating.4 In the first class, the electrolyte has little or no solvent action on the coating that is formed. In general, coatings produced under such circumstances are nonporous and non- adsorptive. In the second class, the electrolyte exerts an appreciable solvent action on the coating. These coatings are porous and adsorptive. Finally, for the third class, the electrolyte tends to dissolve the coating about as rapidly as it is formed. This action produces electrolytic brightening or anodic polishing of the aluminum surface and at most leaves only a very thin film of oxide. The nonporous and nonadsorptive type of oxide film is represented by the coatings that are formed when solutions of boric acid are employed as the electrolyte. It is especially significant that these impervious films are formed in electrolytes that exert little or no solvent action on the coating. Where a boric acid electrolyte is used, the coating tends to form rapidly, with the result that the flow of current is soon reduced to substantially zero. This indicates that the growth of the coating has stopped. As a rule, the thickness of the coating is roughly proportional to the voltage employed for formation and the coatings of this type are exceedingly thin. In an electrolyte of this type, the coating has a high resistance when the aluminum is made anode; consequently, any current that may flow (leakage current) is very

Jan 1, 1944

By Charles E. Locke

The little stamp-mill in the mining laboratory of the Massachusetts Institute of Technology and the work done by it have been well described by Prof. R. H. Richards and E. E. Bugbee in a paper read at the Albany meeting of the American Institute of Mining Engineers, February, 1903.' As run for student class-work the mill contains a feeder, stamps, plate, and vanner. Results in the past indicate that the work of these machines is just as efficient as that of a regular mill handling the same class of ore. It has been the custom to obtain ore principally from Nova Scotia, mainly because it is the nearest source of supply, and also because there is a considerable saving in freight-cost as compared with other districts. The gold in Nova Scotia ores is notoriously coarse, and for this reason it is almost impossible to obtain satisfactory results by sampling and fire-assay, unless an extremely large lot of ore is crushed and all of the contained gold pellets are saved. A very interesting and most extraordinary example of this fact has been presented by a recent run in the Technology stamp-mill. Since the capacity of the mill is about 60 kg. per hr., and since in about 5-hr. run the students in any one section have an opportunity to make the necessary study of machines, it usually happens that several runs are made from one lot of ore. When the shipment is received it is first dried and weighed, put through the Blake breaker, set at 1 or 1.5 in., and the crushed product is piled in a cone on the sampling-floor. When the crushing is completed the ore is usually stored away in barrels for future use; it is aimed to have each barrel of

Jan 1, 1914

By Benj. N. Webber

There is a broad analogy between super gene nickel deposits and super gene copper deposits of the porphyry type. Some of the nomenclature of supergene copper may he applied to super gene nickel deposits. The obvious connection between lateritization and supergene nickel concentration requires some clarification of the nomenclature of laterite of ultrabasic rock parentage. Lateritization is a progressive process and the transition products of the laterite profile are a key to the process of nickel concentration since the profile grades from unaltered peridotite to the highly ferruginous ultimate laterite capping. This profile is formed under highly restricted geographic and geologic conditions. Faulting contributes to the formation and localization of the higher grade commercial segregations of nickel. That there may be auxiliary sources of nickel other than olivine is suggested. The volume of peridotite necessary to produce a unit of laterite at any point in a complete profile is calculated on the basis of the chromite content. The lixiviation, transportation, and precipitation of the elements involved is considered and the source of the reagents and chemical mechanisms are suggested. The role of sodium chloride is considered important. The progressive changes in the lateritic profile have an effect on the general process since lateritization takes place in overlapping environmental phases. The mineralogy of laterite and the redistribution of elements is illustrated by compositional curves derived from a completely mature laterite. Nickel scanvenged by iron oxides tends to be redissolved and moves downward to the zone of transitional magnesium silicates where it is reprecipitated. The geometry of the nickel enrichment zone is simple in general, but complicated in detail. Elongated pods of a greater concentration of nickel are indicated to be a reflection of faulting. Lateritization and concentration of nickel may be arrested at any stage and be modified by several factors.

Jan 1, 1973

By Charles M. Rolker

The Allouez Mine is situated in section 31, town 57, north of range 32 west, Michigan. The mine is being worked in a conglomerate bed, which conglomerate is generally conceded to be the continuation of the Albany and Boston conglomerate of Honghton County. Besides the well-known Calumet and Hecla with the adjoining Osceola, both working on the same bed, and the new location, the Seneca, now being tried on the Kearsarge conglomerate, the Allouez Mine is the only one working on a conglomerate bed. The Albany and Boston, in Houghton County, of which, as said before, the Allouez is supposed to be the continuation, shares with all the remaining conglomerate beds, near and around Portage Lake, the property of being non-quartziferous, while the conglomerates of Keweenaw County are all highly quartziferons in character. This change takes place, according to Professor Pumpelly, about six miles northeast of Portage Lake. The Allouez conglomerate, with a dip of 38" 15' and a general course of about 36' east of north, is overlaid by a trap, and has as its footwall an amygdaloid. The trap is followed by a series of amygdaloidal melaphyres and true amygdaloids, further on by the greenstone and ashbed; towards the lake shore alternating traps and conglomerates are found. At the footwall of the Allouez conglomerate, an amygdaloid lies, the thickness of which is not known, which is also the case with the other formations, accurate surveys and geologiwl researches of this district having, as I was informed, never been made. About 198 meters (650 feet), horizontally measured, from the Allouez conglomerate another amygdaloid bed can be traced, on which the present rockhouse stands, further on a melaphyre is exposed, and then follow the diverse conglomerates, the Calumet, the Kearsarge, and Kingston, which, according to the last geological report, are at about the re-

By John T. Norton, V.G. Mooradian

The diffusion of metal atoms into the crystal lattice of another metal and the assumption of regular positions to form a homogeneous alloy are some of the most fundamental phenomena of structural metallurgy. The mechanism of this process has been the subject of a great deal of study from many viewpoints, but the picture is still far from complete. It is generally believed that if one metal is to diffuse into another, the first must have some solubility in the second1. This means that the solvent must be able to accommodate the stranger atoms, either on points of its own lattice or in the interstices between, without losing its own crystal-lographic identity. It is also a general observation that cold-working is a distinct aid in the diffusion process, causing it to take place with greater rapidity at the same temperature or with the same speed at a lower temperature. There is considerable doubt, however, as to the real significance of the deformation in its effect on the diffusion mechanism. Several factors associated with the cold-working may be responsible for the increased diffusion rate. The plastic deformation causes a distortion of the solvent lattice, which may be an aid in the assimulation of atoms of another kind. There are many references2 in the literature that suggest that some distortion or "loosening" of the lattice is necessary for atomic migration and that diffusion cannot take place in the undis-torted lattice. On the other hand, it may be that the cold-working causes an increase in surface of contact between the two metals through fragmentation or provides a more intimate contact that is necessary for diffusion. If it is true that lattice distortion is an important factor in diffusion, it seems as if there should be some particular relation between

Jan 1, 1935

By Charles M. Rolker

THE Allouez Mine is situated in section 31, town 57, north of range 32 west, Michigan. The mine is being worked in a conglomerate bed, which conglomerate is generally conceded to be the continuation of the Albany and Boston conglomerate of Houghton County. Besides the well-known Calumet and Hecla with the adjoining Osceola, both working on the same bed, and the new location, the Seneca, now being tried on the Kearsarge conglomerate, the Allouez Mine is the only one working on a conglomerate bed. The Albany and Boston, in Houghton County, of which, as said before, the Allouez is supposed to be the continuation, shares with all the remaining conglomerate beds, near and around Portage Lake, the property of being non-quartziferous, while the conglomerates of Keweenaw County are all highly quartziferous in character. This change takes place, according to Professor Pumpelly, about six miles northeast of Portage Lake. The Allouez conglomerate, with a dip of 38° 15' and a general course of about 36° east of north, is overlaid by a trap, and has as its footwall an amygdaloid. The trap is followed by a series of amygdaloidal melaphyres and true amygdaloids, further on by the greenstone and ashbed ; towards the lake shore alternating traps and conglomerates are found. At the footwall of the Allouez conglomerate, an amygdaloid lies, the thickness of which is not known, which is also the case with the other formations, accurate surveys and geological researches of this district having, as I was informed, never been made. About 198 meters (650 feet), horizontally measured, from the Allouez conglomerate another amygdaloid bed can be traced, on which the present rockhouse stands, further on a melaphyre is exposed, and then follow the diverse conglomerates, the Calumet, the Kearsarge, and Kingston, which, according to the last geological report, are at about the re-

Jan 1, 1877

By V. G. Mooradian, John T. Norton

The diffusion of metal atoms into the crystal lattice of another metal and the assumption of regular positions to form a homogeneous alloy are some of the most fundamental phenomena of structural metallurgy. The mechanism of this process has been the subject of a great deal of study from many viewpoints, but the picture is still far from complete. It is generally believed that if one metal is to diffuse into another, the first must have some solubility in the second1. This means that the solvent must be able to accommodate the stranger atoms, either on points of its own lattice or in the interstices between, without losing its own crystal-lographic identity. It is also a general observation that cold-working is a distinct aid in the diffusion process, causing it to take place with greater rapidity at the same temperature or with the same speed at a lower temperature. There is considerable doubt, however, as to the real significance of the deformation in its effect on the diffusion mechanism. Several factors associated with the cold-working may be responsible for the increased diffusion rate. The plastic deformation causes a distortion of the solvent lattice, which may be an aid in the assimulation of atoms of another kind. There are many references2 in the literature that suggest that some distortion or "loosening" of the lattice is necessary for atomic migration and that diffusion cannot take place in the undis-torted lattice. On the other hand, it may be that the cold-working causes an increase in surface of contact between the two metals through fragmentation or provides a more intimate contact that is necessary for diffusion. If it is true that lattice distortion is an important factor in diffusion, it seems as if there should be some particular relation between

Jan 1, 1935

By ED. E. Furman, R. H. Atkinson

HITHERTO the practical creep testing of precious metals has received little or no attention. The only previous creep tests of precious metals have been made with wires under conditions such as to yield much more rapid rates of creep than in engineering tests.', ' Up to the present time the value of creep bars of adequate size, in the absence of real need for engineering data, has deterred investigators. However, the increasing use of platinum at high temperatures has demonstrated the need for reliable creep data for the guidance of engineers, especially those engaged in designing certain specialized chemical plant equipment. In order to supply this need, creep tests were conducted at 1382°F (750°C) on 0.290 in. diam specimens of platinum, 90 pct Pt, 10 pct Rh and palladium. The platinum was high purity, nominally 99.95 pct Pt. The 90 pct Pt, 10 pct Rh was of the same high quality as is used for making gauzes for the catalytic oxidation of ammonia. The palladium was also of high purity; two batches of palladium bars were tested, one deoxidized with calcium boride and the other with aluminum. Spectrographic examination of the palladium confirmed its good quality; the only significant impurities apart from the residual deoxidizers were traces of silicon and lead. Procedure The creep bars, which were furnished by Baker and Co. to our specification, were 6 ¾ in. in overall length with a 4½ in. (4 in. gage length) reduced section 0.290 in. in diam and had the ends threaded (?-NC16). It may be of interest that the bars were valued at up to $600 each. The specimens were supplied in a 50 pct cold-worked condition to facilitate attachment of the creep extensometer, which was of the push rod type. Because of the softness of the platinum and palladium, the extensometer rings were secured to the test section by means of circular knife edges instead of the usual pointed set screws. The extensometer rods extended through the bottom of the furnace and readings were taken with a 0.0001 in. "Last Word" dial gage fastened to the rods for the duration of the test. The bars were directly loaded by hanging weights from the lower specimen grip. All tests were conducted at 1382°F ± 2°F, and an effort was made to maintain the temperature gradient over the test section within 2°F. The ends of the furnace tube were packed with asbestos wool, which allowed a very slow circulation of air through the tube. Annealing was accomplished in the creep furnace before the load was applied. The platinum and palladium specimens were annealed at the test tem- perature for about 17 and 24 hr respectively; in the case of the rhodioplatinum it was found expedient to anneal for 1 hr at 1922°F (1050°C). Pilot samples cut from the same stock as the bars were used to check annealing procedures. Pertinent measurements of grain size and hardness were recorded. Results and Discussion The creep data obtained are given in Table I and the creep curves are plotted in Figs. 1, 2, and 3. Two platinum specimens, tested under a stress of 250 psi, had almost identical creep rates at 2000 hr, namely 0.000008 and 0.000009 pct per hr. A third platinum specimen, stressed at 400 psi, had a creep rate at 2000 hr of 0.000026 pct per hr; the reason for a rather sharp decrease in creep rate during the period from 1200 to 1600 hr is unknown. As it was thought that 90 pct Pt, 10 pct Rh would have a lower creep rate than platinum, the first sample was tested at 400 psi; however, the creep rate was approximately 50 pct greater. Microex-amination revealed that differences in grain size might be responsible for the unexpected result, as annealing at 1382°F developed an average grain diameter of 0.0021 in. in the rhodioplatinum specimen compared with 0.004 in. in the platinum bar. Annealing the alloy for 1 hr at 1922°F (1050°C) increased the average grain diameter to 0.0032 in. and materially improved the creep resistance, making it much better than platinum. A second specimen annealed at 1922°F (1050°C) and tested under a stress of 550 psi had a creep rate of 0.000022 pct per hr at 2000 hr, which was still substantially lower than that shown by the specimen annealed at 1382°F (750°C) and stressed at only 400 psi. In contrast to the creep behavior of the platinum and rhodioplatinum specimens, the palladium bars, whether deoxidized with calcium boride or aluminum, were characterized by high first stages of creep. However, after about 1200 hr of test, the creep

Jan 1, 1952

By C. K. Gupta, P. K. Jena

Niobium (columbium) metal in the form of a button has been produced by calciothermic reduction of niobium pentoxide using sulfur as the heat booster. In these experiments with 50 g of niobium pentoxide per batch, the influence of percentage of calcium in excess of the stoichiometric, the percentage of sulfur by weight of the niobium oxide, and the outer-wall temperature of the bomb on the quality and yield of the metal has been studied. The maximum yield on this scale was 78 pct using 50 pct excess Ca and 20 pct of S and at a bomb-wall temperature of 600°C. In experiments conducted on 500 g of niobium pentoxide, reduction with 40 pct excess Ca and 20 pct of S, and at a bomb-wall temperature of 500°C, the.yield of the metal improved to 82 to 84 pct. Some of the reduced-metal samples have been electron-beam melted and the button melts thus obtained have been observed to be extremely ductile and capable of cold reduction to 98 pct without intermediate annealing. NIOBIUM, because of its high melting point (2468oC), its ductility, its resistance to corrosion especially in liquid metals, its high-temperature mechanical properties, and its relatively low capture cross section (1.1 barns) for thermal neutrons, has potentialities as a structural material in the field of nuclear engineering. Niobium and its alloys are also gaining importance in high-temperature technology as components in aircrafts, jet engines, and missiles, electronics, chemical engineering, and surgery. In 1904 Weiss and Aichel 1 produced niobium by reduction of its pentoxide by misch-metal. Since then a large number of investigations have been carried out for the extraction of niobium from its compounds. The various routes through which the metal niobium has been extracted from its compounds can broadely be classified into the following groups: a) reduction of its halides, oxides, and fluo-salts with metals like calcium, magnesium, sodium, and aluminum;2-10 b) reduction of its halides with hydrogen and oxides with carbon or carbides;11-18 c) electrolytic winning from its halides and fluo salts;19-25 and d) thermal decomposition and disproportion ion of its halides26-30 Among the processes in commercial use at present are sodium reduction or fused-salt electrolysis of potassium niobium fluoride, carbide or carbon reduction of the oxide, and hydrogen or metallothermic reduction of the chlorides. In 1907 Von Bolton2 prepared niobium by reducing niobium pentoxide with aluminum. Dennis and Adam-sona attempted reducing the oxide with magnesium powder in argon atmosphere and the resulting metal contained as much as 5 pct O. Mondolfo8 claimed a method for the reduction of the oxides with aluminum. In the case of both magnesium and aluminum reduction, it has been stated31 that by-product oxides such as MgO or A12O3 would involve a major separation problem. Further, in the case of alumino-thermic reduction, the solubility of aluminum in niobium and intermetallic formation have to be reckoned with. In 1922 Bridge3 produced niobium by calcium reduction of niobium pentoxide. Dennis and pdamson' obtained the metal by a similar method with an oxygen content of 0.2 pct. In most of the cases of metallothermic reduction of niobium oxides mentioned above, the metal niobium is obtained in the form of powder. In an attempt to produce massive niobium metal, lock' used iodine as the thermal booster in the bomb reduction of niobium pentoxide by calcium. Massive niobium metal was obtained with a maximum yield of 75 pct containing 0.1 pct 0. Joly32 carried out experiments on calcium reduction of niobium pentoxide on a 2-kg scale using sulfur as the heat booster in a sealed bomb filled with argon. In his experiments, the reaction was initiated by passing a current through niobium spiral wire embedded in the charge. In a typical run consisting of 2000 g of niobium pentoxide, 3100 g of calcium, and 800 g of sulfur (S/Nb2O5 = 3.3), he obtained massive metal in the form of a very uneven mass with a yield of -57 pct. With lower amounts of sulfur and calcium, powder niobium mixed with small metal globules was obtained and the yield was also poor. From these experiments he concluded that this method is not a suitable one for industrial development considering the quality and yield of metal obtainable and the possible hazards with higher ratios of sulfur to niobium pentoxide in the -~charere. In the present work, a detailed investigation on the calciothermic reduction of niobium pentoxide in a stainless-steel bomb in presence of sulfur as the heat booster was undertaken on a laboratory scale.

Jan 1, 1964

By S. W. Miller

DURING the examination of welds made in steel by the oxy-acetylene and electric-arc processes, the writer has met with some unusual structures, which he has not encountered elsewhere. They seem to be quite closely associated with the welding methods used, and characteristic of them, and would seem to be worth noting, especially as the references to them in the literature are few, and their explanation not clear or complete. An introductory word or two about fusion welding may not he out of place. The oxy-acetylene process is based on the great and very local heat generated by the burning of acetylene in the presence of commercially pure oxygen, the two gases being thoroughly mixed before combustion. The theoretical temperature is somewhat under 4000° C., but on account of various losses, the actual maximum temperature is probably about 3000° C. 1 The electric-arc process, using a metal electrode, which is also the filling rod, generates a still higher and more local temperature. The actual temperature of the positive crater of the carbon arc is given as 3500° C.2 No figures have been found for the temperature of the arc using a metal electrode, but it would probably not be very different from that of the carbon arc, and probably higher than that of the oxy-acetylene flame. The greater localization of the electric arc is due to the fact that it is not surrounded by a large envelope flame as well as to its higher temperature; while the oxy-acetylene white cone, or welding flame, in which the carbon of the acetylene is burned to CO, is surrounded and preceded by -a long envelope flame, itself of quite high temperature, in which the CO is burned to C02, and the hydrogen of the acetylene to

Jan 2, 1918

By F. J. Darnell

SINGLE crystals of a-titanium are difficult to obtain because of the phase transformation at 882 °C in which the structure changes from the high-temperature body-centered structure ß to the low-temperature hexagonal close-packed structure a. Preparation of single crystals of a-titanium has previously been accomplished by a strain-anneal method which takes several days and is not generally reproducible. Single crystals as large as 5 mm

Jan 1, 1959

By Ronald R. MacDonald

There is an ongoing need for the abstracting and coding of new information in the energy and environmental studies field for addition to the BIRS system. There are approximately 3000 bibliographic entries coded into the BIRS system. The bibliographic retrieval system was designed to be run by the general data management System 2000. The information system with entries of coal research, land reclamation and other energy and environmental studies is up and on line. As more entries are coded they are loaded into the system.

Jan 1, 1977

By F. P. Dewey

Rich Hill is situated in the famous car-wheel iron region of Southwestern Virginia, and although it contains many iron ores, this paper will be devoted chiefly to its car-wheel ore. Geologically, Rich Hill is somewhat difficult to describe, as the strata of the region are seriously folded and contorted. It lies at the base of one of the primordial spurs of the Blue Ridge, the ore appearing as a sedimentary deposit on the limestone No. 2, sometimes showing an imperfect stratification, but generally being an

Jan 1, 1882

By F. P. Dewey

RICH HILL is situated in the famous car-wheel iron region of Southwestern Virginia, and although it contains many iron ores, this paper will be devoted chiefly to its car-wheel ore. Geologically, Rich Hill is somewhat difficult to describe, as the strata of the region are seriously folded and contorted. It lies at the base of one of the primordial spurs of the Blue Ridge, the ore appearing as a sedimentary deposit on the limestone No. 2, sometimes showing an imperfect stratification, but generally being an

Jan 1, 1882

By William P. Blake

In southern Arizona and in Mexico the word caliche is in general use to denote a calcareous formation of considerable thickness and volume found a few inches, or a few feet, beneath the surface-soil, upon the broad, dry, gravelly plains and mesas. , In western South America the same name is applied to the beds of crude soda-niter (Chili saltpeter). While these deposits of South America and of Arizona are totally different in composition, and have nothing in common, except that both occur in

Jan 1, 1902

By Paul Wilkinson

From the earliest times, the principal component of mallplaster has been ordinary lime. Plaster-of-Paris has also been known from early times, but never used to any extent in the actual base-work of plastering-materials; it is generally used for finishing over the brown coat and for ornamental work. As an illustration of the antiquity of the use of gypsum-plaster for mortar, I find that the analysis of the exterior covering of the pyramid of Cheops, as made by Dr. Wallace, is almost identical

Jan 1, 1898

By Lloyal O. Bacon

In the spring of 1952 Calumet and Hecla Inc. began a geophysical program near Shullsburg, Wis., in the Wisconsin-Illinois lead-zinc district, to assist the geological and drilling exploration programs. Sphalerite, the ore mineral in this area, occurs with a considerable amount of marcasite. In general the higher the percentage of sphalerite in the ore, the higher the percentage of marcasite; however, there may be mineralized zones high in marcasite but low in sphalerite. Orebodies in general are relatively narrow and elongated.

Feb 1, 1956