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By R. P. O’Shea

AS part of a program to investigate phase relationships in ternary systems containing semiconducting elements and compounds, an X-ray survey of alloys in the system Pb-Te-Bi was carried out which revealed that the pair PbTe-Bi probably formed a quasibinary system. This portion of the ternary was examined fully by thermal analysis, X-ray, and microscopic procedures. More than twenty-five alloys were made by melting together the proper combinations of the elements in quartz tubes at a temperature of 1000o C. The compositions which were high in PbTe content were prepared in evacuated, sealed, quartz tubes, allowed to freeze in vacuum, and then transferred to Crucibles for thermal analysis. The bismuth-rich alloys were made directly in the crucibles under a protective gas cover. The starting elements were obtained from the American Smelting and Refining Co. and had a purity greater than 99.99 pct. Cooling curves were made with about 50 g of alloy in graphite crucibles which were placed in a covered quartz container in which a protective atmosphere of helium or nitrogen was maintained. The thermocouple protection tube was made of mul-lite and served as a stirring rod when connected to a reciprocating stirring motor. Temperatures were

Jan 1, 1962

By C. B. Smith, A. G. Guy

The power and convenience of tensor analysis are employed in deriving the equations that describe three-dimensional diffusion in an n-component system plus vacancies. A "Kirkendall coordinate system, '' defined in principle by Kirkendall markers, is used in defining the intrinsic diffusion coefficients that are of primary interest. The defining equations are then transformed to local cartesian coordinates and to fixed cartesian coordinates, the latter being convenient for experimental measurements. Finally, it is shown how the intrinsic diffusion coefficients can be calculated from the experimentally determined quantities. It is generally recognized that any treatment of the essential diffusion phenomena in metallic systems—the jumping of atoms from one lattice position to another—must be based on movement of the atoms past Kirkendall interfaces.' A logical extension of this idea is the proposal that, fundamentally, diffusion must be described mathematically in terms of "Kirkendall coordinates." The basic equations thus obtained may then be transformed into other coordinate systems, when such transformation leads to simplification of either the experimental or mathematical treatment of diffusion data. Tensor analysis is clearly the appropriate mathematical tool for this purpose, since it provides methods both for determining general equations that are valid for all coordinate systems and for conveniently transforming the equations from one coordinate system to another system related to the first in some known fashion. For the present purpose three coordinate systems are used, and it is convenient to begin with a description of the relations among these three systems. FICK LAW FOR KIRKENDALL COORDINATES The reference coordinate system, and the one that is useful for most experimental measurements, is a cartesian coordinate system, xi (i = 1, 2, 3), fixed with respect to some point in the specimen, such as an end of the alloy bar undergoing diffusion. A second set of coordinates, the Kirkendall coordinate system, is one that in principle can be described by the location of inert markers (Kirkendall interfaces). A convenient mathematical relation between Kirkendall coordinates, x'i, and the reference cartesian coordinates, ii, is obtained by specifying that the Kirkendall coordinate system coincide with the cartesian system at time, t = 0. After diffusion has occurred for some time, t = t, the Kirkendall coordinate system will differ from the reference system in the manner shown schematically for the one-dimensional case in Fig. 1. The third coordinate system is Darken's1 local cartesian-coordinate system, xi, which is identical with ii in orientation and units, but which moves with the point under consideration in the Kirkendall coordinate system. Even though most diffusion problems are essentially one-dimensional, there is an advantage in first carrying out the analysis of the three-dimensional problem to gain a clearer insight into the assumptions that are made in the usual one-dimen-

Jan 1, 1962

By N. A. Tiner

A study was made of the effects of temperature, type of loading, and electric polarization on the fracturing behavior of copper and zinc coated with mercury. Copper showed an em-brittlement only in cyclic loading, whereas zinc showed an em-brittlenzent in both static and cyclic loading. The embrittle-ment of zinc in static loading was prevented by sub-zero cooling to a temperatzcre of about -70°F. The emhrittlement of both metals was sliglztly reduced by cathodic polarization of mercury. The basic processes involved in fracturing were discussed in the light of these observations. When a solid metal is in contact with certain liquid metals possessing high wetting characteristics, a weakening effect is produced, and the solid metal fractures in brittle manner at a relatively low stress. This lowering of the fracture stress generally is considered different from the stress cracking caused by a corrosive liquid environment and is attributed to the lowering of the solid-liquid interface tension at the grain boundaries.1-4 The purpose of this paper is to describe a number of observations on the special features of fracturing of copper and zinc coated with a liquid mercury film, and to analyze the basic processes involved in fracturing in the light of these observations. EXPERIMENTAL OBSERVATIONS I) Effect of Type of Loading—The evidence appears to indicate that in static loading, metals usually fracture by the initiation of microcracks in the interior preferentially at the grain boundaries or at the intersection of slip bands.' In cyclic loading, cracks develop on the surface within the active slip zones, and gradually propagate with increasing num- ber of cycles.6'7 Because of this difference in the manner of initiation of cracks, a series of bare and mercury coated copper and zinc specimens was subjected to static and cyclic loading, and their fracturing behavior was examined. The specimens were machined to 0.25 in. in diam and 1 in. in length from a high-purity commercial bar stock, and annealed at an appropriate temperature. Mercury was applied to the surface of the specimens by rubbing with cotton wool soaked in a saturated solution of HgCl2 or by etching with a dilute solution of HC1 and rubbing with purified mercury and by washing in water. The static tension load-extension curves were obtained by means of a Riele Screw Power Universal Testing Machine. The room-temperature load-extension curves for copper and zinc are shown in Fig. 1. The deformation behavior of copper, as judged from the general configuration of the load-extension curve, was not affected by mercury coating. The maximum load to fracture and the elongation at the maximum load were practically the same for both specimens. The mercury coated copper, however, showed somewhat less localized necking and had smaller reduction of area than the uncoated metal. The behavior of mercury coated zinc was radically different from the behavior of uncoated metal. The load-extension curves were the same at the

Jan 1, 1962

By Dale A. Vaughan, Oliver M. Stewart, Charles M. Schwartz

Solid-solubility limits at 1500°, l000q and 500°C for carbon, nitrogen, and oxygen in high-purity tantalum were determined by X-ray lattice-parameter methods. For carbon, the solubility was found to be 0.17 at. pct at 1500°C, and less than 0.07 at. pct at 1000°C. A nitrogen solubility of 3.70 at. pct at 1500° C decreases linearly with temperature to 2.75 at. pct at 1000°C, and 1.8 at. pct at 500°C. In the case of oxygen, the solubility was found to be 3.65 at. pct at 1500°C, 2.95 at. pct at 1000°C, and 2.5 at. pct at 500°C. The phases Ta2C, the low-temperature modification of Ta205, and Ta,N of unknown composition but which has a superlattice structure based upon the original bcc tantalum lattice have been identified as the initial precipitates in the respective systems. Metallographic methods were employed to verify the X-ray analyses. The etching behavior of Ta is discussed in terms of lattice i?rzperfections and precipitate phases. The excellent fabricability, high melting point, and nuclear properties of tantalum are responsible for interest in this refractory metal. Data on the solid solubility of the interstitial elements (oxygen, nitrogen, and carbon) in tantalum and on the precipitate phases are somewhat limited. The significant contributions are discussed below. Because the purity of electron-beam melted tantalum (only recently available) is considerably higher than that used in previous studies, the present investigation was initiated. Gebhardt et all-3 have investigated the tantalum-oxygen and tantalum-nitrogen systems with particular reference to the changes in physical properties and to the rates of reaction between these gases and the metal. The solubility of oxygen in tantalum was reported2 to be 3.7 at. pet at 1500°, 2.3 at. pet at 100O°C, and 1.4 at. pct at 750°C. Schonberg4 reported that several oxide phases (Ta40, Ta,O, TaO and Ta,05) exist while X-ray studies by Gebhardtl showed only two oxides, Ta,05 and an unidentified phase which was associated with a platelet-type precipitate. La-gergren and Magneli,' however, questioned the existence of compounds other than the two allotropic modifications of Ta,05 for the tantalum-oxygen system. In the case of nitrogen, the solubility was estab- lished by Gebhardt3 to be of the order of 7 at. pct at 1800°c. The solubility was reported to decrease rapidly with temperature, and, although no limits were established, a precipitate phase was observed by Gebhardt except when the high-nitrogen specimens were cooled very rapidly from the reaction temperature of 1800c. He reported the initial precipitate phase to be a tetragonal distortion of the bcc tantalum lattice while Schonberg6 reported the phase lowest in nitrogen Jo be a cubic super-lattice with a cell size of 10.11 A. Two other nitride phases, Ta,N and TaN, were reported; these appear to be isomor-phous with the carbides of tantalum. The tantalum-carbon system was investigated by Ellinger7 and by Lesser and Braurer. Two compounds, Ta,C and TaC, were reported to exist, each with a range of composition. The solubility of carbon in tantalum was found to be practically nil at all temperatures. Thus, of the interstitial elements which are present in small amounts in high-purity tantalum, carbon might be expected to form precipitates. The present investigation was initiated to obtain additional data on the solid-solubility limits of these interstitials at 1500°, 1000°, and 500' with particular emphasis on the distribution and the identification of the precipitate phases. EXPERIMENTAL WORK AND RESULTS In the present investigations of the solid solubility and of the precipitate phases in the systems tantalum-nitrogen, -oxygen, and -carbon, high-purity tantalum was reacted with high-purity gases, homogenized at 1800°c, and annealed at and quenched from 1500°, 1000,

Jan 1, 1962

By C. G. Dunn, J. L. Walter

COULOMB' and Coulomb and Lacombe2,3 have recently discussed secondary recrystallization in soft iron (99.5 pct Fe). They found that the appearance of this phenomenon was dependent on both the presence of impurities and the thickness of sheet specimens. They concluded that impurities such as carbon, sulfur, and oxygen in the soft iron stabilized the matrix structure and allowed growth of a few grains of specific orientations. They also found that secondary recrystallization ceased when the final thickness was small and attributed this complete inhibition of growth in thin sheet to the restraining action of thermal grooves. When purer iron (99.99 pct Fe) was used, normal grain growth but not secondary recrystallization was obtained. On the other hand it is known that the necessary stabilization of the matrix structure for secondary recrystallization in high-purity silicon iron probably does not depend on impurities but more likely results from the specimen thickness effect of Beck et al.,4 according to evidence and ideas advanced by Walter and Dunn,5,6 and Detert.7 Furthermore, Mullins8 has indicated that if a gas-metal surface energy difference exists across a grain boundary equal to or greater than about 3 pct of the grain boundary energy, then such a grain boundary should not become stuck. Similarly, Walter and Dunn have estimated that any increase in restraining force due to increased thermal grooving with decrease in

Jan 1, 1962

By O. Herstad, J. M. Toguri, K. Grjotheim

DURING the last three years, investigations on the aluminum reduction of magnesium-bearing compounds have been initiated at the Institute of Inorganic Chemistry, The Technical University of Norway. The results of these investigations are reported in this paper. Very little information exists in the literature on the reaction between magnesium compounds and metallic aluminum. The available information itself is conflicting, and, to clarify the existing discrepancy, the reactions between aluminum and magnesium oxide (MgO), caJcined dolomite (CaO . MgO) and olivine (Mg2SiO.) were studied. The logical approach for the study of these reactions between condensed states with the formation of a gaseous phase is, ( 1) the measurement of the equilibrium vapour pressure of the gas, in this case magnesium, associated with the respective reactions and, (2) the identification of the end products of the reaction in order to establish the re-action scheme.

Jan 1, 1962

By Ralph C. Flow

In Cleveland County, North Carolina, one and one-half miles south of Kings Mountain, Foote Mineral Company operates an open pit for the production of spodumene, feldspar, mica, and commercial stone. Spodumene concentrate is sent to Footers Sunbright, Virginia plant and to other customers. Exton, Pennsylvania and New Johnsonville, Tennessee plants produce lithium compounds sold to the oil industry for multipurpose lithium-base greases, to the metal industry as welding flux, to the air conditioning market, and to the glass industry. Ceramic grade spodumene, feldspar, and mica concentrates go to other processing companies from the Kings Mountain plant. Waste amphibolite is delivered to a neighboring quarry operation.

Jan 1, 1962

Differentiation of a basaltic (?) magma occurred in an active volcanic area during the late Miocene and Pliocene, and a change in the general mode of extrusion from fissure flow for the basalt to explosion for the andesite reflects an accompanying increasing magmatic viscosity. A caldera formed after the flow phase was completed and was filled with coarse agglomerate, much of which has a fused appearance. After an erosion interval its shape was modified and it became gradually deeper as repeated explosions from growing andesitic volcanoes caused large quantities of pyroclastic material to be deposited. At the close of this phase the floor abruptly collapsed when a, large block of the underlying crust was engulfed. The incompetent pyroclastics filling the caldera steepened in dip and the ensuing fractures were filled by the rising magma as dykes and sills and a chonolith formed below the caldera at a shallow depth. The ensuing activity reveals a further stage in differentiation and biotite is an important new ferromagnesian to be observed in the new rocks.Fracturing of the surrounding basalts was most intense in the rocks forming the periphery of the caldera where steeply and flatly dipping faults resulted from increasing horizontal pressure directed towards the caldera.Further differentiation resulted in the increased crystallization of orthoclase felspar, as evidenced by the numerous intrusives of trachy andesitic composition. Magmatic freezing caused mineralizers to accumulate at the top of the chonolith. These eventually escaped and auriferous pyrites, tellurides, quartz, and calcite were deposited in the surrounding rocks.The flatly dipping fractures are the most important and can be expected at various depths in a zone about 4,000 ft wide surrounding the caldera. Latest movement along these was controlled by magmatic consolidation rather than the shape of the caldera. Some flat faults were able to remain open during mineralization and acted as a feeder for the shallower fractures, thus limiting the depths to which the steeper dipping fractures were mineralized with the possible exception of one particular Nw.-striking lode (the Crown-Crescent).INTRODUCTIONThe gold deposits of the Tavua district were discovered in 1932 and from 1935 to June, 1961, 1,985,041 fine ounces of gold were produced from 4,202,504 tons of ore. Of the original three producers, only the Emperor remains active in the...

Jan 1, 1962

By L. W. Rowe, S. S. Cole

A laboratory bench scale unit is described whereby finely divided chlorinatable residues are held for a short period by a restraining bed of a coarse-grained ore of comparable composition to permit 'flash' chlorination of the high surface area powder. Results on chlorinating a finely divicled titania residue using rutile sand as the restraining bed showed that 92 pct utilization of chlorine and equivalent conversion of TiO2 in the fine residue to Ticl4 were attained with a dust loss of about 3 to 4 pct and an equivalent amount of ch1om'nation of the titanium values in the restraining bed. THE chlorination of coarse grain titaniferous ores; i.e., 20 to 150 mesh sizes in fluidized beds is practiced commercially.' One effective method found for the chlorination of a very fine material in a fluidized bed is the "flash" chlorination technique.' By charging the finely divided charge material into the bottom of an established bed of optimum sized rutile, ilmenite, titanium beneficiate, or even an inert material such as sand, chlorination occurs before the dust can pass through the bed. The major requirement is that the bed be less chlorinatable than the charge. In this process, the charge consists of a finely divided (between one and 50 µ) titania residue obtained from a titaniferous ore beneficiation process. The charge is blended with a 20 pct wt basis addition of 20 to 60 .mesh size low volatile coke (to minimize hydrogen chloride formation) and fed to the bottom of the bed with the chlorine gas stream. A ball check device is used to permit entry of the charge and prevent the bed from discharging when the gas flow is cut off. The coarse pieces of coke serve to reduce compaction in the charge mixture and permit sat]sfactory feeding without plugging or jamming. Feed and gas rates are adjusted to provide for complete reaction of the charge material, with 90 to 95 pct chlorine efficiency, and maintain a gas flow in the range of 0.4 to 0.6 ft per sec. The equipment consisted of a 3-in. diam mullite tube enclosed in an electric furnace. A bow-shaped 3/4 in. Saran tube fed the charge from an air lock type of feed hopper (to prevent the escape of the chlorine gas into feed bin) to the bottom of the bed. The charge rate was set by providing a small awiliary hopper below the feed hopper where a weighed portion of the charge could be discharged in a specified time interval into the main chlorine stream. The chlorine rate was measured by a flowmeter. The reaction tube was filled with a bed of Australian rutile ore, this restraining bed serving two purposes; i.e., it rapidly heated the fresh charge to the reaction temperature and retained the particles in the bed for a sufficient time for selective chlorination to proceed. Due to the fine particle size and open, porous structure of the charge, this reaction was almost instantaneous, and, with proper adjustment of feed and gas rates, very little fine material passed through the bed without reacting and only a very small fraction of the restraining bed was chlorinated. A typical reaction procedure was to fill the bench scale fluidized bed unit with a 1 kg charge of Australian rutile ore analyzing 95.5 pct TiO2, 0.6 pct FeO, a beach sand deposit 40 to 150 mesh size. When fluidized, the bed was approximately 2 ft in depth. The ore was fluidized with a 1:l mixture of chlorine and nitrogen at a rate of 0.40 ft per sec. This gas mixture was necessitated by the comparatively short bed depth; a larger unit, with a deeper bed, could be fluidized with chlorine alone without significant free chlorine loss. Feed rate was 8.0 g per min of beneficiated ilmenite analyzing 85.0 pct TiO2, 2.6 pct FeO plus 1.6 g per min of 20 to 60 mesh petroleum coke. The

Jan 1, 1962

By J. E. Hilliard

It is proposed that shape anisotropy in the internal structure of materials be defined by distribution functions which specify what fraction of the total line length or boundary area lies in a given direction. Methods are descriibed for determinirg these distribution functions from measurements on sections through an opaque material. New derivations, that have certain advanifages over those given previously, are Provided for well-known expressions used in estinzating the total density of lineal or areal features. INCREASING attention is being given to the quantitative description of imicrostructures in metals and other materials. This interest stems from the recognition that the structure often provides a convenient half-way point between the properties on the one hand and the processing variables on the other. Such cross correlations become increasingly desirable as materials become more complex and the demands on them more stringent. One of the principal aims in structure analysis is therefore to find parameters that are readily measurable and specific enough to be correlated with other properties of the material. Certain properties, such as magnetic and mechani cal behavior, are strongly influenced by structural anisotropies; in order to relate such properties to the structure it is obviously necessary to have means of specifying and measuring the type and degree of anisotropy. For the determination of preferred orientations in crystal structure, X-ray diffraction methods are available and are widely used, but scant attention has been given to the estimation of anisotropy in the shape of grains and particles. It is the latter problem that will be considered in this paper. It is evident that shape anisotropy can be describe in terms of preferred orientations of lineal and area elements of the structure. It will be shown that these preferred orientations can, in turn, be specified by distribution functions that define what fraction of the total line length or boundary area lies in a given direction. Methods will be given for determining the distribution functions from measurements on sections through the structure. Even when the orientation distributions are of no interest per se, they still have an important bearing on the measurement of the total line length or boundary area by means of an intercept analysis. The treatment in terms of orientation distribution functions leads to new derivations, that have certain advantages of those given previously, for the well-known expressions used in estimating the total density of lineal or areal features. The treatment is divided into two main sections. The first deals with the orientation distribution of a two-dimensional array of lineal features such as occurs in the projected image of dislocations in electron transmission microscopy. The other section treats the estimation of the distribution of lineal and areal features dispersed in three dimensions.

Jan 1, 1962

By P. E. Doherty, B. Chalmers

Subboundaries may be revealed in aluminum by the formation of pits on the surface during cooling from elevated temperatures. The pits do not form in the vicinity of high- or low-angle boundaries. They are attributed to the condensation of vacancies from a super saturation produced during coolirzg. Using the vacancy pit and Schulz X-ray techniques for observing low-angle boundaries, a study was made of the transition from the nearly perfect seed to the striated structuke characterist-ic of aluminum crystals grown from the melt. It was found that the individual striation boundaries develop by the coalescence of very small-angle boundaries, as well as by the addition of individual dislocations. Several mechanisms for the formation of striations are discussed. Evidence was found suggesting that a super-saturation of vacancies exists near a growing interface, and it is proposed that the resulting climb of existing dislocalions produces "half'-loops" at the interface, which combine to form the low-angle striation boundaries. LINEAGE, or "striation" boundaries, have been studied in detail by Teghtsoonian and Chalmers 1,2 in crystals of tin grown from the melt, and by Atwater and Chalmers3 in lead. They found that single crystals grown from the melt consist of regions which are separated by subboundaries that lie roughly parallel to the growth direction. A difference in orientation of 0.5 to 3 deg exists between the striated regions; the misorientation is such that the lattice of one region could be brought into coincidence with the lattice of its neighbor by a rotation about an axis approximately parallel to the direction of growth of the crystal. They observed an incubation distance for the formation of striations which increased with decreasing growth rate. They also found that in any crystal, the sum of all rotations of the lattice in one sense, in going from one striation to the next, is very nearly equal to the sum of all the rotations in the opposite sense. A striation boundary, which is a low-angle grain boundary, can be described as an array of dislocations. If it is assumed that suitable dislocations are introduced into the crystal during solidification, the formation of striation boundaries can be explained as a result of the migration of the disloca- tions into arrays. The formation of arrays is energetically favorable since the energy of an assembly of dislocations can be reduced by the interaction of the stress fields when a suitable array is formed. This investigation presents and interprets new information concerning the nature and origin of striation boundaries in aluminum. EXPERIMENTAL TECHNIQUE Single crystals of high-purity aluminum (Alcoa 99.992 pct) were prepared by horizontal growth from the melt.'' The specimens were subsequently electropolished in a solution of 5 parts methanol to 1 part perchloric acid kept between -10° and 0°C in a bath of dry ice and alcohol. The current density was approximately 6 amps per sq in. Doherty and Davis9 have shown that in aluminum sub-boundaries with misorientations of not less than several seconds of arc may be revealed by the vacancy pit technique. During cooling from elevated temperatures pits form on electropolished surfaces of aluminum crystals as a result of the condensation of vacancies.11 Pits do not form in the vicinity of small- or large-angle grain boundaries, presumably because such boundaries act as sinks for vacancies. Boundaries of misorientations down to 3 sec of arc are revealed as pit-free regions, see Fig. 1. The Schulz X-ray technique12 was used to determine the angular misorientations of subboundaries. In this method, white radiation from a micro-focus X-ray tube is used to produce an image of a fairly large area of a single crystal surface. Subboundaries cause splitting in the diffracted image, see Fig. 2. Misorientations down to about 15 sec of arc may be observed with this technique. OBSERVATIONS AND DISCUSSION Figure 1 shows a striated aluminum crystal grown at 10 cm per hr etched by the vacancy pit technique. An incubation distance of about 1 cm is observed before the initiation of striation boundaries. Fig. 2 is a Schulz X-ray photograph of a striated crystal similar to that shown in Fig. 1. A large area of the crystal was studied by means of a series of photographs. Fig. 2, which is a reflection from the (100) plane, included about the first 4 cm of crystal to freeze. There is an incubation distance of about 1 cm, and a distance of about 2 cm over which the angle of misorientation builds up to its final value of approximately one degree. Some twist component can be seen in Fig. 2 at the right side of the photograph. From Fig. 2 it can be seen that the sum of all rotations of the lattice in one

Jan 1, 1962

By J. H. Holden

Operations involving the processing of coal, oxygen, and steam into synthesis gas by means of two pressure-type gasifiers have demonstrated the effect of heat loss and operating variables on carbon gasified and oxygen and coal requirements. Carbon gasified is the fraction of carbon in the coal that is converted to gas. Oxygen and coal requirement is the quantity of each that is needed to produce a unit volume (M std. c.f.) of carbon monoxide and hydrogen. Operating pressure of the gasifiers ranged from 150 to 300 p.s.i.g. and coal was fed at 200 to 500 lb./hr./cu.ft. of reaction-zone space. Oxygen-to-coal ratios were 8.5 to 10.5 std. c.f./lb. Heat loss and residence time have opposite effects on carbon gasified; increasing the heat loss decreases the carbon gasified, but increasing the residence time (by raising the operating pressure or reducing the coal-feed rate) increases the carbon gasified. The effects of these two factors are difficult to separate because they usually change simultaneously. A comparison of the results obtained from the operation of two gasifiers with different levels of heat loss, however, permitted the effect of heat loss to be separated from that of pressure and coal-feed rate. When the results were deter- mined on the basis of constant heat loss, increase of the residence time increased the carbon gasified until the reaction virtually had come to completion. For example, at 150 p.s.i.g., decreasing the coal-feed ratio from 500 lb./hr./cu.ft. to 200 lb./hr./cu.ft. substantially increased the carbon gasified. At 300 p.s.i.g., however, changing the coal-feed rate had little effect on the carbon gasified because the reaction had almost reached completion and further increase in residence time resulted only in a negligible change.

Jan 1, 1962

By J. G. Haymes

This report by the Bureau of Mines is the first of two proposed papers on evaluation of spectrophotometric, spectrographic, polarographic, and other analytical methods for quantitatively determining impurities in high-purity tungsten. Some of the methods described are standard methods that have been successfully applied to determine low-level impurities, several are modifications of known methods, and some procedures are entirely original. The Bureau of Mines is actively engaged in tungsten research because tungsten has an extremely high melting point, in fact the highest of any known metal. The metallurgist must know the content of impurities in tungsten because of the marked effects even micro amounts of impurity elements have on its physical properties. The Bureau procured a number of analyzed samples of above-average purity from research laboratories of companies engaged in production and fabrication of tungsten. These samples were investigated by the analytical procedures of those companies for several metallic impurities. Subsequent analytical laboratory determination of impurities in these samples agreed with the analyses as reported. With this assurance that analytical methods were basically accurate for metallic impurities, procedures for the determination of several of these elements were modified to lower the limits of detection and increase the sensitivity of methods. Carbon and the gases hydrogen, nitrogen, and oxygen were determined by standard instrumental methods, modified to provide greater sensitivity for reliable determinations when content of these elements was low. After the reliability of the modified procedures was affirmed, they were used as a product evaluation guide in the development of a vapor-plating technique for the production of high-purity tungsten. The following list of elements can be determined by one or more of these methods: AI, B, Be, Ca, Co, Cr, Cu, Fe, Mg, Mn, Mo, Ni, Pb, S1, Sn, Ti, V, and Zn. In addition, a vacuum-fusion method for the determination of H, N, and 0, and a conductometric method for carbon are described. Lower limits of determination and detection for each element listed are given.

Jan 1, 1962

By R. W. Stahl

An emergency is defined as an unforeseen combination of circumstances that calls for immediate action. When applied to a coal mine, an emergency may call for prompt removal of the men to the surface through travelways other than the haulageway or intake airways, which are generally contaminated with irrespirable air as a result of an explosion or fire. Therefore, maintenance of adequate and travelable escapeways from all working areas of a mine is vitally important insurance against disaster. Several mine disasters could have been avoided if well-defined escape routes had been provided and made known to all mine employees. Such occurrences, unnecessary as they generally are, unfairly indict the industry when only a small segment thereof is involved. As a result of a rather recent disaster, which might not have happened if good escape routes had been provided, the Bureau of Mines decided to delve into the escape procedure to determine (1) what is being done in the industry and (2) what might be done at reasonable cost.

Jan 1, 1962

By George C. Carter

It was just a little over three years ago that the "Go" button was pushed to start operations on the blending piles at Oro Grande. As is usual with any new installation, there were problems that had to be solved. This paper will concern itself with those problems directly related to quality control. To obtain a consistent outgoing quality level at the most economical level for a finished product requires two main points: 1. Measurement of variations in the process, 2. A method of making a predictable change to adjust for variations. The manufacture of cement requires a relatively high degree of accuracy if a consistent outgoing quality level is to be maintained. The blending piles were our solution to this problem.

Jan 1, 1962

By G. V. Sullivan

This report summarizes the results of a preliminary study concerning manganese extraction from low-grade dolomitic materials from the Philipsburg district in Montana by the Dean-Leute ammonium carbamate process. Studies were made to determine the relationship between the variables involved in treating these materials by a roast-leach process and the amount of manganese extracted. The variables studied were the roast temperature, the roast particle size, the molar ratio of NH3 to CO2 in the leach solution, the liquid-solid ratio in leaching, the leach time, and the size of the particles being leached. The roast-leach studies were statistically designed, and the experimental results were evaluated by an analysis of variance.

Jan 1, 1962

By Hsun Hu

Direct observations were made on the recrystalli-zntion of a cold-rolled (110) [001] crystal of 3 pct Si-Fe by annealing thin sections of the specimen inside the electron microscope during examination. Subgrain formation, presumably by polygonization, occurs rapidly, followed by a slow increase in the subgrain size before recrystallization can be detected. No migration of the subgrain boundaries was observed, and the formation of recrystallization nuclei by coalescence of subgrains is suggested. Re-c~ystallization characteristics of various texture components were individually examined. AS reported in a previous paper: orientations of the various deformation texture components in a 70 pct cold-rolled (110) [0011 crystal of 3 pct Si-Fe were completely confirmed by transmission electron diffraction patterns taken at various areas of the specimen. These orientations can be summarized as follows: Over most areas of the deformed crystal (111) planes are parallel to the surface. These areas correspond to either $- the two main defor: mation textures, the (111) [112] or the (111) [112].2-5 Within a few areas, (100) planes parallel to the surface are frequently found. These areas represent the minor deformation texture component, the (100) [Oll] type, which is derived from rotated Neumann bands.2'4'5 Only in very rare instances are (110) planes found parallel to the surface. This orientation corresponds to the very weak texture component of the (110) [001] type. In a pole figure, this (110) [0011 orientation is located within the orientation spread between the two main (111) [1121 type textures. Usually the electron diffraction patterns taken at various areas of the specimen are very simple ones, i.e., for any one area the pattern consists only of sharply defined spots of a single orientation. In some areas, however, more or less continuous rings of weaker intensities are superimposed on a simple pattern, indicating the presence of a wide range of additional orientations. In order to understand in detail the recrystallization of this cold-worked crystal, the recrywtallization characteristics of each of the various deformation texture components must be examined. This can best be done by using a high-temperature stage and transmission electron microscopy techniques, whereby small areas corresponding to the various texture components can be selected individually for examination. The present paper presents results obtained by this method. MATERIAL AND METHOD Specimens were prepared from a previously studied1 single crystal of a commercial grade 3 pct Si-Fe alloy with an initial orientation (110) [00l], cold-rolled 70 pct from 0.014 in. to 0.004 in. in thickness. Thin foils were prepared by electrolytic polishing as described in the earlier paper.' Specimens of this thin foil were then mounted in a high temperature stage similar to the one designed by Whelan.6 A direct current was used as the heating source. The temperature of the heating grid was calibrated by means of a Pt vs Pt-10 pct Rh thermocouple in a vacuum chamber (0.01 to 0.02µHg). Maximum variation within the temperature range of 250o to 000°C was about ± 25°C. After the desired areas were selected for examination, the specimen was heated to a low temperature for some time while the selected area was constantly watched. When no further change in structure and orientation could be observed, a higher temperature was applied. Photomicrographs and diffraction patterns were taken from time to time during examination, with the heater temporarily turned off* while the photographs were

Jan 1, 1962

By Larsen. Edward P.

The principle of "bed blending" in the agglomeration of materials is about 56 years old, but de- spite all education via technical papers, operating reports and results from functioning installations, the concepts of blending are still somewhat vague. Confusion exists between "mixing", "blending," and the basic role of each. The terms "blending" and mixing" are often used interchangeably, yet they describe two different processes. As properly understood and applied, a blend is a combination of different varieties of material which produces a desired quality, or the mingling of different elements to form a harmonious whole. In other words, blending is a process of combining granular materials by mechanical means, wherein the final product, or a portion thereof, must contain an exact proportional amount of every one of the several different materials which contributed to the mass and wherein all particles are so thoroughly intermingled with each other as to have lost their individual identities and become a part of the whole so that when a portion of the blend is taken at any time it will be substantially identical, chemically and physically, to any other portion taken throughout.

Jan 1, 1962

By V. F. Swanson

As part of the Bureau of Mines titanium resources examination program, samples of altered rock (saprolite) and unaltered rock from the Roseland anorthosite near Roseland, Nelson County, Va., were tested for amenability to beneficiation by flotation. A flotation technique was developed to produce bulk concentrates of ilmenite, rutile, sphene, and leucoxene. It was necessary to first float apatite using oleic acid as the collector, in an alkaline pulp with dextrine as a titanium mineral depressant. The titanium minerals could then be floated from the apatite tailing, using fluosilicic acid to depress the remaining apatite, morin to depress ferromagnesian minerals (when present), and oleic acid as the collector. A bulk titanium mineral concentrate, analyzing 66.0 percent Ti02 and 0.08 percent P205, was obtained from a sample of the unaltered rock which contained 5.45 percent TiO2 and 2.81 percent P205. Overall recovery in the concentrate was 47.1 percent of the total TiO2 in the ore. About 55 to 65 percent of the saprolite sample was clay and was removed by attrition scrubbing and decantation. The apatite prefloat procedure was applied to the saprolite sands; subsequent titanium mine: 1 flotation recovered 72.2 percent of the Ti02 in a bulk concentrate containing 65.1 percent TiO2 and 0.20 percent P205.

Jan 1, 1962

By I. C. Edwards, D. C. Smith

THE milling plant of Bicroft Uranium Mines Limited at Ban-croft, Ontario, was one of the first in Canada to employ ion excl1ange for the selecti1•e recovery of uranium from acid leach liquors. The ion ex-change circuit started operating early in November, 1956, and by June 1 I959, had handled more than two million tons of pregnant solution containing I,830,000 pounds of U3Os. Each column had been saturated and eluted about 430 times. The ion exchange columns are the conventional fixed bed type. Uranium is eluted from the resin with a sodium chloride-sulphuric acid solution and is precipitated continuous-ly with magnesia. After filtering and drying, the precipitate, or "yellow cake," is packaged in drums for shipment to the refinery.

Jan 1, 1962