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By Y. L. Yao

THE NaT1-type compound may be considered as the penetration of two diamond lattices in such a way that a superstructure of the bcc lattice is formed. Examples of the NaT1-type compound of lithium are LiZn, LiCd, LiA1, LiIn, and LiGa. Except for LiZn and LiCd, each molecule of these equiatomic compounds contains a total of four valence electrons. In LiZn and LiCd it was suspected (for example, see Ref. 1) that the fourth electron was withdrawn from the 18-shell of zinc or cadmium. An incomplete 18-shell would have to show strong paramagnetism. In 1955 Klemm and Fricke2 determined the magnetic susceptibility of LiZn, LiCd, LiA1, and LiIn (also NaTl and NaIn). The molar susceptibility of the outer electrons of LiZn and LiCd was found to be not strongly but weakly positive; that of LiAl and LiIn not negative but weakly positive. Thus they questioned the hypothesis about LiZn and LiCd in particular and the description of the NaT1-type structure in general. However, they did not determine the magnetic susceptibility of LiGa. This note is to report results for all five compounds of lithium. The starting materials are 99.9 pct pure lithium sticks containing less than 0.005 pct Na. 99.9 pct Zn, 99.9 pct Cd, 99.99 pct Al, 99.999 pct In, and 99.999 pct Ga. Weighed amounts of two components were wrapped in tantalum foil and placed in a graphite crucible. It was found that the tantalum sheath minimized the vaporization losses of lithium during melting. The sheath was easily stripped from the alloy rod and the tantalum in the alloy was barely detectable (less than 0.01 wt pct). The melting was performed in a resistance furnace under an argon atmosphere. Alloy specimens were annealed for 1 hr at 400°C in vacuum. The magnetic susceptibility at room temperature was determined by the Faraday Method, using the procedures previously described.' The results are shown in Table I. The interpolated values at 50 at. pct of Li and the average values at 48 to 52 at. pct of Li at 20°C determined by Klemm and Fricke2 are also shown. It is seen that the present value for LiZn and LiCd is slightly more positive but the present value for LiAl and LiIn is slightly less positive than their corresponding values. Also, it is noted there is an abrupt decrease of susceptibility of LiAl from 51.2 to 52.5 at. pct of Li. Klemm and Fricke2 found that the total susceptibility of LiZn, LiCd, LiA1, and LiIn is almost independent of temperature. slater4 gave a working expression for the diamagnetism of the atomic core as follows:

Jan 1, 1964

By T. Szaplonczay, D. E. Light

The auto-oxidation of sulfur dioxide to form sulfuric acid in commercially produced barren and recycle liquors, containing 1.66 and 4.56 gpl Fe respectively, from Elliot Lake was studied. A gas mixture, containing 3.5% SO2 and air was introduced into these liquors through a frit at a rate of 6.0g SO2 per hour per liter of solution. The barren and recycle were heated to 60°C. At the end of the first 24 hours of the process the concentrations of acid produced were 158 and 220 gpl H2SO4 for the barren and recycle respectively. Corresponding conversion efficiencies were 70 and 83%. In the period from 24 to 36 hours the rate of acid production decreased so that the H2SO4 concentrations at the end of 36 hours were 180 gpl for the barren and 260 gpl for the recycle; average conversions for the initial 36 hours were 55 and 68% respectively. Many investigators1'2'3 have considered the oxidation of sulfur dioxide to form sulfuric acid in aqueous solutions containing metallic ions. A summary of the work performed on this subject prior to 1946 has been presented by Keyes4 who described the auto-oxidation process as follows. Keyes also suggested that in this second reaction ferric ion serves as a catalyst for the conversion of sulfur dioxide to sulfuric acid. Neytzell-de Wilde and Taverner5 have reported on the use of auto-oxidation to produce a 4 to 5% sulfuric acid solution for use in a cyclic leach process at South African uranium plants. This paper describes investigations carried out to determine the feasibility of using the auto-oxidation process to produce sulfuric acid solutions of as high concentration as possible using commercially produced uranium plant barren and recycle liquors from the Elliot Lake region of Ontario. These liquors contained 1.66 and 4.56 gpl respectively of iron, chiefly in the ferrous state. This investigation is of particular interest to the uranium producers in Elliot Lake where the ores contain 3 to 4% sulfur, as sulfides. Flotation of these sulfides and roasting of same to produce SO, bearing gases have been successfully demonstrated using conventional methods.6'7 Barren and recycle solutions, as described previously, are also produced in large tonnages by these uranium producers. The experimental method and apparatus used to examine the auto-oxidation process will be described first. Then the tests carried out on laboratory prepared aqueous solutions containing ferric sulfate to determine optimum conditions will be presented. The next section will describe the tests using the commercial barren and recycle liquors. A final section will summarize the conclusions of the work. EXPERIMENTAL APPARATUS AND PROCEDURES Two types of solutions were used in the tests, a laboratory prepared aqueous solution containing definite amounts of ferric sulfate, and commercially produced iron bearing solution obtained from a uranium leaching plant in the Elliot Lake area. Two liters of a solution to be examined were placed in a 3 in. diam by 30 in. long glass cylinder with a cross-sectional area of 7 sq in. A mixture of air, and SO2 supplied from a lecture bottle for convenience, was introduced into the bottom of the vessel through a standard 30 mm glass frit, 700 sq mm in area. The temperature of the apparatus was controlled by a heating tape and variable transformer. Exhaust gases were vented to atmosphere. At the end of the test period the gas flow was shut off and the solution was analysed for H2SO4, Fe ++, and Fe +++, by conventional means. Four variables were examined using the laboratory prepared aqueous solution of ferric sulfate. First, the effect of SO2 concentration, from 1 to 1076, in the feed gas mixture was considered. Second, the temper-

Jan 1, 1964

By G. Koves

The behavior of case-hardened AISI C-1213 free -machining steel under complex impact-fatigue -wear load conditions was investigated. The inherently poor dynamic properties of the steel are mainly affected by the stress distribution in the case, component shape, and tempering. Cold-riveted components showed unexpectedly high dynamic strength compared to basic parts. A compromise beatment—which provides good dynamic properties, reasonable wear resistance, and fair riveting characteristics—zuas developed. A number of mechanical components in data-processing machines are made of free-machining carbon steel. Although, selected primarily due to manufacturing requirements, components made of these grades frequently undergo complex heat treatment and must sustain impact-fatigue loads. A typical free-machining steel is the AISI C-1213 grade, which is a resulfurized and rephosphorized open-hearth steel. While the undesirable effects of sulfur and phosphorus on the mechanical properties are well-known, data on dynamic properties are scarce.1"3 Rapid rotating or oscillating motion while carry- ing a high cyclic load requires a combination of wear resistance with high endurance limit and impact toughness. The inherently poor dynamic properties of the free-machining steel are further degraded by the machining, which introduces local stress-concentration areas. While the heat treatment (usually case hardening) improves some mechanical properties, it necessarily impairs others. Another problem arises when components, such as studs, must be fastened by riveting. The high crack-sensitivity of the free-machining steel, especially in the presence of a hardened case, makes this operation difficult. In view of the preceding considerations, it is of interest to investigate the behavior of a typical component under complex impact-fatigue-wear loading conditions in order to explore the effects of material, machining, and heat treatment, to obtain specific data on the dynamic characteristics of free-machining steel, and to arrive at a process which would adequately utilize the inherent qualities of this material. EXPERIMENTAL PROCEDURE To simulate actual service conditions, a typical component was selected, based on frequency of application, complexity of load, and processing difficulties. The dimensions and shape of the component—a stud used in many electromechanical document-handling machines—are shown in Fig. 1.

Jan 1, 1964

By R. B. Toombs

In describing the Canadian mineral industry in a world setting, this paper examines the industry from four points of view. First, mineral industry growth is related to trends in economic activity thereby providing a measure of the industry's importance in the Canadian economy. To give perspective to the Canadian scene, reference is made to economic trends in several of the world's leading mineral producing and mineral consuming countries. The Canadian mineral industry is next examined in terms of its major developments of the past 20 years and the resultant size, structure, and production diversity of 1964. The position of the Canadian mineral industry in the world industry is then analyzed by tracing changes in mineral supply and demand patterns. Growth of the Canadian industry depends greatly on expansion of export markets because three fifths of the value of production is accounted for by exports. Finally, attention is directed to the outlook for the Canadian mineral industry. Problems facing the industry are surveyed, and an appraisal is made of economic policies that have encouraged industry growth. A forecast of mineral production value in 1970 is included.

Jan 1, 1964

By J. K. Brooke

Fluorine is a lively element in both its chemical and economic behavior. It was not isolated as an element until 1886 by Moissan. However, its principal source to this day, fluorspar, was known and its special merits recognized long before that time. Our own mining brother, Agricola, is credited with having named fluorite, the mineral name, in 1546 from the Latin, "fluere", to flow. It made things melt and was already being used as a flux. Because fluorspar has been found as a relatively common gangue mineral in metal ore veins, it has long attracted the attention of geological thinkers seeking to, explain the whys and wherefores of veins. Fluorine has been thought of as one of the principal mineralizers, holding metals in ascending vein solutions for deposition close enough to the eventual surface to be accessible for profitable mining.

Jan 1, 1964

By C. R. Hubbard

The Bureau of Mines investigated the mineral resources of the Upper Missouri River Basin as a part of a comprehensive water and related land resources study by six Bureaus of the Department of the Interior, coordinated by the Department's Missouri River Basin Field Committee. The mineral resource study covers an area of about 18,000 square miles within the Great Plains physiographic province of central Montana. Exposed Formations in the plains are chiefly flat-lying Cretaceous sediments. Plutonic rocks crop out in the central parts of the mountain uplifts, with steeply tilted Paleozoic sediments exposed around the margins. Oil and gas have been produced from several fields in the study area; total value exceeds $45 million. Coal-bearing formations of Upper Jurassic and Cretaceous age cover approximately 45 percent of the study area. Total production of coal since 1880 has been between 40 and 50 million tons, exceeding $75 million in value. Total metal production has been about $52.5 million. Industrial mineral production from 1925 through 1960, is valued at $24 million.

Jan 1, 1964

By T. B. Massalski, Horace Pops

The occurrence and the temperature dependence of the athermal martensitic transformation in bcc Cu-Zn ß-phase alloys have been studied by cold-state microscopy, differential thermal analysis, and electrical -resistivity measurements. CinenzatograpJzic studies have shown that in the majority of alloys the transformation occurs in two stages. A thermoelastic phase, having a 'needlelike" uppearance, forms initially at the MS temperature and grows relatively slowly, chiefly in the edge (lengthwise) direction. With further cooling, an additional martensitic phase forms in rapid bursts at a lower temperature, MB, Both martensitic phases appear to have the same cry stallographic habit hut their modes of formation and growth are different. For the composition range studied, between 38.55 and 41.49 wt pct Zn, the habit planes determined are close to the (2.17 ,12) plane of the matrix, in general agreement with the prediction of the phenomenological theory of martensite formation. Thermal cycling through the MB temperature produces permanent plastic deformation in the 0 matrix and gradutally eliminates the typical burst phenomena. Thermal cycling only through the MS temperature produces no noticeable deformation effects. THE bcc Cu-Zn ß-phase alloys tend to become unstable at low temperatures and undergo a martensitic transformation,'-3 but the details of the transformation have not been completely determined. Following earlier metal log raphic and X-ray work1 Tichener and ever' determined by means of electrical-resistivity measurements the temperature range of the martensite transformation during continuous cooling. The transformation temperature was found to decrease with increasing zinc content, becoming about -130°C for an alloy containing 40.04 wt pct Zn. Hull and Garwood3 made a metallo-graphic study of Cu-Zn 0 brasses at temperatures down to -160°C, and determined the habit plane of the transformation product for an alloy containing 38.88 wt pct Zn. No metallographic studies below liquid-nitrogen temperatures have been reported. The martensitic transformation in ß-brass alloys can also be induced by deformation.1,4 The MD temperature corresponding to the appearance of the strain-induced martensite is some 300°C higher than that observed without strain, and hence the transformation can be strain-induced in alloys containing a higher percentage of zinc. Massalski and Barrett4 found that alloys containing as much as 51.89 wt pct Zn could be transformed into a faulted hcp structure by cold working at liquid-helium temperature. Because the details of the MS temperature and morphology reported in the literature are somewhat incomplete, a further study has been made of some of the above features. A design of a cryogenic stage for optical metallography5 has permitted the examination of specimens at temperatures down to 4.2oK, and the use of a cinecamera has permitted a study of the morphology on cooling and heating. The particular aim of the present work was to examine the transformation temperatures, the habit planes, and the growth morphology over a wide composition range in the ß-phase field. The effect of thermal cycling upon the subsequent transformation was also examined.

Jan 1, 1964

By C. E. Silverblatt, D. A. Dahlstrom

Previous bench-scale studies demonstrated that a substantial moisture reduction can be obtained by the application of steam to coal filter-cakes, particularly to those containing a limited amount of minus 200-mesh material. Consequently, U.S. Steel's Applied Research Laboratory conducted a study to determine the feasibility of steam filtration of 1/4 in. by 0 coal on a continuous pilot-scale installation in which an Eimco extractor is used. The test results showed that the moisture content of this coal could be reduced to 5.5% at a steam loading of about 175 lb of steam per ton of dry cake. In terms of steam consumption, this loading is calculated to be 1-1/2 lb of steam per lb of water removed. In some tests, only 1 lb of steam per lb of water removed was required. These levels of steam consumption are significantly less than the actual heat requirements of conventional thermal dryers. The satisfactory moisture reductions were obtained at filtration rates of 125 to 186 lb of dry solids per sq ft per hour. However, the proper design of commercial filters should improve the potential rates that can be attained. These results indicate that steam filtration has considerable economic potential for drying 1/4 in. by 0 coals and also has additional advantages over the conventional thermal drying of coal. The results of the previous bench-scale studies and those published by Burton' demonstrated that a substantial moisture-content reduction can be effected by the application of slightly superheated steam to coal filter-cakes, particularly to those containing a limited amount of minus 200-mesh material. Consequently, US Steel's Applied Research Laboratory conducted a study to determine the feasibility of steam filtration of 1/4 in. by 0 coal on a continuous basis. In the continuous process, the dewatering operation on the filter is conducted in stages. In the first, the bulk of the water in the feed slurry is removed by conventional mechanical dewatering on a portion of the filter before the steam is applied. In the second stage, steam is applied to the cake. The steam condenses and releases its latent heat, thereby reducing the viscosity of the remaining cake water; this reduced viscosity then facilitates further drainage and produces a cake of lower moisture content. Because of the availability of feed coal on a continuous basis and since steam was readily available from a low-pressure boiler, the Applied Research Laboratory selected for the test site a coal-preparation plant that cleans Pittsburgh Seam coal. A slurry of table and flotation coal in percentages as they occur normally was used as feed stock. Typical analyses of this slurry are shown in Table I. DESCRIPTION OF FILTER AND EXPERIMENTAL PROCEDURES An Eimco Extractor was selected for the evaluation of steam filtration in a continuous process. This unit was chosen because of its availability and its design features that permit relatively simple hood construction, instrumentation, and operation. A photograph of the Extractor is shown in Fig. 1. In the filter a cloth medium is used that travels horizontally and continuously with a grooved, rubber drainage belt. The total effective filter area was 12.5 sq ft. As the feed slurry flows by gravity from the feed box onto the medium,

Jan 1, 1964

By R. E. Reed-Hill, J. L. Martin

Kinking is an important deformation phenomenon in poly crystalline a zirconium. The crjlstallo-gvaphic features of the most important form of kinking have been determined with the aid of twins formed at 77°K in grains previously kinked at high temperatures. It has been .found that the kink-band boundaries correspond to walls of edge dislocations with (1150) Burgers vectors and dislocation lines parallel to (1070). The present observations imply that basal slip is an important secondary-slip mode in polycrystalline zirconium. Previous single-crystal studies13 did not veveal this mode Other evidelzc.e for (0002)(1120) slip is also presented. ThE first studies of kinking in hexagonal metals were made by orowan,1 using single-crystal cadmium wires. He suggested that this was a new de- formation mode in metals, different from ordinary glide or twinning. Next, Hess and Barrett2 studied zinc-crystal rods in compression, and were able to offer an explanation of the phenomenon described by Orowan. They concluded that kinks required no new deformation mechanism and were a special form of deformation band that developed gradually and solely from basal glide. Similar kink bands were then observed by Washburn and parker3 on zinc crystals deformed in tension at low stresses and high temperatures. In titaniun,4 kink bands associated with {1010}<1120> prism slip have been observed in coarse-grained specimens. Magnesium5 and rhenium6 have also been observed to kink in conjunction with their basal- and {1010} prism-slip systems, respectively. Yttrium has (1010) as a predominant slip plane, but no observations of kink bands were reported.7 Since no previous investigations of kink bands in zirconium have apparently been made, this study was proposed. Its aim was to determine the crys-tallographic features of a type of kink band frequently observed in polycrystalline zirconium. EXPERIMENTAL APPARATUS All tests were performed on a type TTC Instron machine. The cross-head speed usually chosen in tension or compression was 0.02 in. per min. Ten-

Jan 1, 1964

By Richard D. Miller

This publication contains routine analyses and related source data for 350 natural gas samples from 19 States collected during calendar year 1962 as part of a continuous survey of the United States for occurrences of helium in natural gas. This survey has been conducted by the Helium Activity of the Bureau of Mines since 1917. The analyses published herein were made by mass spectrometer and a special helium analysis apparatus. Four previous publications have been made to present the results of 5,648 gas analyses made by the Bureau of Mines, Helium Activity, prior to 1962. The first, Bulletin 486, 3/ contains analyses and data on 2,195 gas samples collected during the period 1917-47. Bulletin 576, 4/ the second publication, includes data and analyses for 1,575 samples collected from 1947 through May 1956. The third bulletin 5/ contains 1,444 analyses and source data of samples obtained from May 1956 to January 1, 1961.

Jan 1, 1964

By R. A. Limons

Natural ores, sinters, and pellets were subjected to a carbon monoxide reduction-disintegration test under laboratory conditions including a simulated blast furnace gas and a 1000°F temperature. The most significant findings were that: 1. Self-fluxed pellets broke down to a greater extent than either the acid pellets or the acid or self -fluxed sinter. 2. When pre-reduced, both the acid and self-fluxed pellets had very good resistance to breakdown.

Jan 1, 1964

By W. Rostoker, H. Nichols

It has been demonstrated in previous work1&apos;2 that wetting of aluminum alloys by liquid mercury can cause fracture to occur with substantial suppression of prior plastic flow. This has been interpreted as the action of a critical liquid species in reducing the cohesive strength of a stressed solid at sites of potential crack nucleation. In this way the critical transverse stress for fracture nucleation is reached at much lower stresses than is normally the case. The stresses for both fracture nucleation and fracture propagation are depressed by the same mechanism. In so doing the plastic-energy component of fracture energy is reduced to a level which is of the same order of magnitude as the surface, interfacial, or cleavage energy. Recent work2 has illustrated the influence of dispersed precipitates, cold work, and combinations of these on brittle fracture associated with plastic strains of the microyield order of magnitude. This has been rationalized in terms of the contribution of internal microstress fields to the stress magnifications at points of obstruction of active slip bands in a stressed metal. The presently reported studies on an Al-4-1/2 pct Mg alloy amplify this subject by introducing thermal-mechanical conditions which can produce strain aging. As amply demonstrated by Phillips, Swain, and borall, the tensile behavior of aluminum alloys containing magnesium reveals a yield-point elongation and successive discontinuous elongations over the whole plastic-strain range. This gives a stepped or serrated character to the stress-strain diagram. The yield-point elongation is not temperature-dependent. On the other hand, the discontinuous extensions in the plastic-strain range are gradually suppressed by lower temperatures of testing. At -78"C, only the yield-point elongation persists. The yield-point elongation itself can be suppressed by rapid quenching to room temperature from an annealing temperature of 500°C. The argument presented by Phillips et 1. and Cottre114 is that the yield-point elongation derives from surmounting at a critical stress the restraint to slip by grain boundaries which have been reinforced by appreciable magnesium-atom segregation. The serrated character of the plastic-strain range is the result of rapid strain aging during the test. This is made possible by the inevitable proximity of magnesium atoms to any dislocation line. In the Al-4-1/2 pct Mg alloy there is one magnesium atom for every twenty-two aluminum atoms and, with a coordination number of 12, a magnesium atom is on the average only about two atomic distances from any given lattice site. Rapid strain aging is therefore a reasonable expectation. A study of mercury embrittlement of the Al-4-1/2 pct Mg alloy (commercial designation 5083) provides an opportunity to relate the interplay of grain size, grain boundary restraint to slip and strain aging in the brittle-fracture process. One lot of commercial sheet material of 0.125-in. thickness was used for all of the tests. The specimen shape and test procedures used were the same as those described in a previous publication.2 A range of grain sizes between 0.0057 and 0.0125 mm was produced by various combinations of plastic prestrain and annealing. The coarsest grain was somewhat elongated in shape. In this case the measurement was taken in the direction transverse to the axis of tension as more meaningful to a brittle-fracture process. In the annealed condition, specimens wetted with mercury failed with zero permanent elongation at stresses slightly below the normal yield point, i.e., stresses at 0.05 to 0.2 pct strain. Since this occurs before yield-point elongation can begin, fracture derives from slip contained within individual grains and restrained from propagating across grain boundaries. No significant difference in wetted fracture stress was observed between specimens which had been water-quenched or furnace-cooled from the annealing temperatures. This signifies that the degree of magnesium segregation at grain boundaries

Jan 1, 1964

By J. H. Bain, D. C. Haigh, L. C. Parsons

Jan 1, 1964

THE developments in construction and operation of the basic open-hearth furnace that have taken place in recent years have placed new emphasis on the vital influence played by regulation and control of the combustion system in both furnace production and furnace life. The several factors influencing flame development, such as regulation of fuel supply, air supply, air preheat, furnace draft, and furnace reversal, must be controlled closely if successful furnace performance is to be accomplished. Rugged instrumentation of distinctive design is required to sup- ply dependable information concerning operating conditions, which is requisite to proper regulation of combustion. This chapter attempts to give a practical discussion of the various features of open-hearth practice and instrumentation related to the efficient heating of the furnace, control of temperature, and protection of the furnace structure from accidental overheating. The appended references will be helpful to readers wanting a more detailed treatment of individual topics. OPEN-HEARTH FUELS The most important open-hearth fuels are listed in Table 4-1 together with their compositions and other data useful for combustion calculations. A detailed discussion of open-hearth fuels is not attempted here, but certain factors peculiar to their application to this type of process are briefly indicated on the following pages. Very often an open-hearth shop is forced by economic factors to use a fuel to which its furnaces are not very well adapted, because the general fuel-allocation scheme for the works as a whole seems to demand it. Often a variable marginal supply of coke-oven gas or tar must be consumed by the open hearth, together with another fuel such as producer gas, natural gas, or oil, to fill out total requirements. Most furnaces employ more than one kind of fuel during their useful life; however, the partial redesign

Jan 1, 1964

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&apos; 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&apos; 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 Lynce AJ

A method has been developed for the prediction &apos;of &apos;the- . performance of a multi-stage grinding=cyclone classification circuit of any degree of complexity on any ore for a wide range `of operating conditions, The-.method involves ;the. s` inu ation b&apos;f the circuit on a digital computer by means of. matheinatical&apos; models ":bf the"&apos; individual units:, the. development of which is- also discussed&apos;., At present, in order to establish &apos;the!&apos;" charac&apos;teristtics of they ¦ore- and the machines. in mathematical terms;. it is necessary to know&apos;the performance of a , simpl,.e. ; system on tri.e ore - for! one known ,,feed rate and.fe.ed s,l-zing, analysis. &apos; ,Fiiither work on :the- separate identification &apos;of the terms defining the characteristics of the ore and the machines may permit the method to be, applied directly to the cj.4ta,derived from small scale tests on ores,

Jan 1, 1964

KNOWING the endpoint, or the equilibrium state, in steelmaking reactions is only part of the story. The rate at which the reactions proceed can be equally important. But the power of thermodynamics, which enables us to estimate the endpoint, is that a knowledge of the mechanism is not required. The methods of kinetics, however, are step-by-step analysis in which a knowledge of the detailed reaction mechanism is essential. As is evident from Chapter 16, a great deal of thermo- dynamic data for steelmaking are available and the underlying theory rests on a completely sound basis. This is far from the case with kinetic data and even kinetic theory. Nevertheless, it is worthwhile to examine the present state of knowledge, to see how far it may be applied to electric furnace reactions. KINETIC THEORY Heterogeneous Reactions. Classical kinetic theory and experimentation have been mainly concerned with homogeneous reactions taking place between different chemical species in a gas or liquid phase. The species are mixed together and the progress of the reaction can then be observed. This is possible because most experiments have been done at relatively low temperatures where the characteristic time for the mixing process is much shorter than the time for the chemical reaction to be completed. For example, in the homogeneous gas reaction, H2 (g) + I2 (g) 2HI (g) hydrogen and iodine may be added to opposite ends of a tube containing a diaphragm. When this is withdrawn, gaseous diffusion (and convection) mixes the two types of molecule almost completely before any hydrogen iodide molecules begin to appear. Such an experiment is inconceivable at more elevated temperatures, since the rate of the chemical process is so sensitive to temperature that reaction would be completed almost instantaneously wherever hydrogen and iodine came into contact; the rate of the mixing process would then determine the rate at which hydrogen iodide was formed. We should not, therefore, expect to observe many homogeneous reac-

Jan 1, 1964

By E. F. Poncelet

Forty years ago A. A. Griffith developed a theory explaining why brittle materials displayed such low tensile strengths.&apos; He based his views on two points. First, he found himself compelled to assume that all brittle materials are replete with flaws, cracks, and other defects that act, although quite invisible, as large stress raisers. Second, he applied the "theorem of minimum potential energy," which says that the total potential energy of a system must pass from the unbroken to the broken condition by a process involving a continuous decrease in potential energy. By this means he satisfactorily accounted for the noted low strength of such solids and also for the wide spread obtained in experimental measurement of these strengths. So successful has the theory been that it is favored by some to this day. Unfortunately this theory is of limited use beyond the explanation of these two noted phenomena and it is keenly felt that a better theoretical insight into the physics of the fracturing process is needed as the volume of experimental evidence accumulates. The author proposes in the following to build on the fundamentally sound concepts of Griffith and, with the help of increased theoretical knowledge over that available to Griffith, develop a mechanism for frac-ture which will provide far greater understanding of the experimental evidence accumulated to date than is possible from the original Griffith idea. THE GRlFFlTH THEORY Very little progress indeed can be made without accepting the first postulate of Griffith which supposes all brittle solids to be full of microcracks. It would be difficult indeed to find a better mechanism for the small strength of such brittle materials, in conjunction with the fact that the energy that must be expended for comminution is by no means small. The postulate of the existence of the microcracks permits the breakup of the various bonds a few at a time by concentrating the stress at the tip of the progressing crack, while the total energy expended is the same as if they all had been ruptured simultaneously. The only flaw in the argument is that no reasonable explanation has been proposed to account for the genesis of such cracks. Indeed their very presence is in violation of the Griffith second postulate, the potential energy theorem. This theorem is straightforward for isothermal processes, and, in spite of Griffith, there is some doubt that treating the problem isothermally is legitimate. The surface energy of bodies is a free energy, not a potential energy as stated by Griffith, and the production of new surface free energies is not necessarily an isothermal process. There is ample evidence to the contrary. Generally speaking, if heating a body increases its surface area, then, by virtue of Le Chatelier&apos;s principle, any increase of that area by other means will tend to lower its surface temperature. Lord Kelvin calculated the actual cooling that resulted in drawing out a film of liquid.2 R. A. Houston calculated the surface cooling that resulted in stretching a metal wire.3 These calculations were made by applying the Carnot cycle to the process and evaluating the thermodynamics thereof. IRREVERSIBILITY OF THE FRACTURING PROCESS While Griffith was very careful not to say so, the impression gained from studying his papers is that he considered the fracturing process as reversible, that is, a succession of quasi-equilibrium states. There is ample evidence that it is not. The indication that the new surfaces produced by the propagation of a crack are cooler than the original body points to an irreversible heat flow from the interior to the new surfaces to equalize the temperatures. If the process be reversible, any crack accidentally formed should immediately close up as, in the absence of any strain energy, the potential energy would thereby be lowered. The fact that they do not, constitutes a paradox. Such paradoxes are nothing new where certain phenomena that propagate from minuscule nuclei are assumed to be reversible. Such is, for instance, the condensation of a pure saturated vapor that is suddenly chilled by adiabatic expansion. At the beginning the tiny droplets that are formed should be only a few angstroms in size, but the vapor pressure at such droplets is so high that they should evaporate at once. A similar situation arises if a saturated pure solution becomes super-saturated upon cooling; the first tiny crystal nuclei should dissolve as fast as

Jan 1, 1964

By O. B. Buchlen, J. W. Smith

The Coal Research Bureau of the School of Mines at West Virginia University, using an experimental flotation cell designated an airlift-cyclone was able to obtain a clean coal product containing 7.64% ash with 94% yield and 97% coal recovery. This favorable performance was obtained with the experimental flotation cell operating as a simulated three-stage unit on slurry taken from the fine coal circuit of a coal preparation plant. This experimental device, consisting of a sheet metal cyclone-like unit mounted on a U-shaped uplift pipe, uses a combined flotation and cyclone action to beneficiate the minus 14 mesh partially cleaned feed product. In addition to providing comparable analytical results, the airlift-cyclone possesses other attractive features among them being a low capital expenditure, utilization of moderate plant floor space, efficient operation on high density feed slurry, and absence of moving parts. The primary shortcoming of the experimental cell is its limited capacity. The Coal Research Bureau presently has under construction a larger unit which, it is hoped, will provide the capacity and quality to establish the airlift-cyclone as a commercially feasible unit. Froth flotation of fine coal is a practice which has only recently gained wide acceptance in this country. Various explanations can be put forth for this delayed acceptance of a very selective and efficient system of coal preparation. Among these reasons would be the advent of continuous mining machines resulting in the increased production of coal fines, the change in market patterns from domestic and rail consumers who did not want fines to a predominantly utility market which normally consumes fines, and also the imposition of legal restrictions in regard to stream pollution. However, the major detriment is probably the high cost involved both in installation and operation of the flo- tation unit and auxiliary systems. These facts assume greater emphasis when considering that froth flotation installations normally process a low quality feed product. A recent estimate&apos; of installation costs including dryers, filters, and other auxiliary equipment for a flotation system was $5000 to $7000 per ton of capacity while the operating costs, exclusive of auxiliary equipment, were estimated at 10 to 306 per ton of feed. The Coal Research Bureau of the School of Mines at West Virginia University is currently developing a simplified froth flotation cell, designated an airlift-cyclone, which may provide considerable savings in capital and operating costs without sacrificing product quality or recovery. This experimental cell consists of three primary components: 1) a vertically mounted U-shaped pipe; 2) an air injector device; and 3) an integrally mounted cyclone-like unit (Fig. 1). A feed slurry is introduced at the top of one leg of the U-pipe while compressed air is injected near the base of the other leg. The air serves both to aerate the pulp and to cause it to flow upward into the base of the cyclone unit where the floated clean coal is separated from the reject material and unfloated coal which remains in slurry. The Coal Research Bureau&apos;s experimental airlift-cyclone is somewhat similar in principle to a flotation device developed by Russian engineers in the late 1950&apos;s. In tests upon a two-stage pilot-size device, the Russians obtained very favorable cleaning efficiencies.&apos; However, later experience with production models demonstrated that rated capacities and acceptable product quality could not always be maintained.3 Because of these limitations, Russian engineers subsequently recommended that conventional, mechanical cells be used when cleaning difficult to float slurries. Engineers at the Coal Research Bureau felt that such a device utilizing the combined actions of a cyclone and a froth flotation machine offered numerous attractive features and merited investigation. Accordingly, a small capacity experimental airlift-cyclone was designed and, with the permission of the Christopher Coal Company Div. of Consolidation Coal Co., installed in Christopher&apos;s Humphrey preparation plant near Morgantown, West Virginia.

Jan 1, 1964

By Charles T. Baroch, Charles J. Baroch

Nuclear energy probably has greater potentialities for changing the world&apos;s way of life than any other recent discovery. The atomic-bomb bursts over Hiroshima and Nagasaki suddenly changed the concepts of war. Peaceful uses of nuclear energy are advancing so rapidly that no study of economic trends is complete without giving them consideration. The minerals specialist, especially, must be aware of this new force in our lives, as minerals and metals are essential in harnessing the new force, and atomic energy itself is rapidly improving its competitive position in the energy field. Future historians may chronicle December 2, 1942, as the beginning of the Atomic Age. On that day Enrico Fermi and his co-workers at the University of Chicago produced and controlled the first self-sustaining nuclear chain reaction. Lie many inventions, the first application of nuclear energy was as a weapon of war. However, its potential usefulness in man&apos;s work and welfare far outweighs in economic importance its destructive use in war, unless its military effect would be considered so great and all-embracing that no major power will hereafter chance a world conflict. Recognition of this potential has generated a vast international effort to exploit the atom for peaceful beneficent purposes. Like its physical manifestation, the advent of nuclear energy has unleashed chain reactions that have pervaded the political, social, and economic environments of the world. The impact of nuclear developments in one of many fields is exemplified by the uranium mining industry. Uranium was discovered in 1789 and in the next century and a half it found only an insignificant use as a ceramic coloring agent; in fact, in the latter part of that period, it was a largely unsalable by-product of the radium and vanadium industries. Up to 1940 the total quantity of uranium metal produced was not more than a few grams, of doubtful purity. Thus the production of 12,400 pounds of pure

Jan 1, 1964