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By James P. McGee

Preliminary calculations show an economic advantage in using nuclear energy to supply the endothermic heat required for gasifying coal. It should be noted that the various assumptions used in preparing these calculations must undergo further evaluation through additional engineering design and research. The proposed system for gasification is the indirect process cycle with helium heated in a nuclear reactor and passed through an exchanger-type gasifier for the reaction of coal and steam to form CO (carbon monoxide) and H2 (hydrogen gas).

Jan 1, 1960

By D. F. Stoneburner, G. Derge, Ling Yang

PREVIOUS investigations in this laboratory have shown the existence of electronic conduction in several molten metal sulfides and the specific conductance of a number of these has been measured as a function of temperature.' In order to better understand the electronic nature of these melts, the thermoelectric power of a molten FeS-solid tungsten thermocouple was measured and a value of approximately 55 µv per "C was obtained in the temperature range from 1200" to 1400c2 These studies have been continued and the thermoelectric power of several other molten metal sulfide-solid tungsten thermocouples have been obtained. The experimental arrangement is shown in Fig. 1. A Kanthal furnace was used, doubly wound to prevent any undesirable effects of an external field. A 1/2-in. McDanel tube was fitted with two vertical 5/8-in. McDanel tubes as shown. These tubes were about 2 in. apart. A graphite boat was used to hold a re-crystallized alumina boat in which the prefused sulfide was placed. Two probes were made using

Jan 1, 1960

By R. L. Stanton

"The present contribution examines, in some detail, what appear to be the three outstanding features of the field occurrence of the conformable ""pyritic"" deposits. These are their association with fragmental volcanic rocks (and derivatives), their occurrence in sediments of near-shore formation, and their highly variable structural associations.In a recent paper it has been suggested that two such ""pyritic"" de-posits in New Brunswick may have originated as marine concentrations of volcanic base metal and sulphur compounds, and that many of their present features are the result of diagenesis, folding, and regional metamorphism. This is now put for-ward as a general explanation for the particular class of deposit considered.Such deposits should, on this hypo-thesis, be regarded quite simply as an integral part of the particular geological environment in which they occur -as a normal, though minor, sedimentarry type developed, char-acteristically, in near-shore and shelf facies of intravolcanic units formed along the margins of eugeosynclines. They should not be considered -as, for example, is required by the re-placement theory -as later features simply superimposed on a geological situation to which they are genetically unrelated. Where they are associated with folds and other structures, this may be attributed, from one in-stance to another, to mechanical migration during folding, weaknesses induced by pre-existing sulphides, and, occasionally, to fortuitousness.In the light of this postulated origin, it is suggested that the first stages in regional prospecting for deposits of this particular class should be broadly palaeogeographical. Later phases of the search should then be directed to the delineation of sedimentary facies and, finally, to the investigation of geological structure."

Jan 1, 1960

By W. M. Dressel

A simple, reliable field test for beryllium in rocks has been developed by the Rolla Metallurgy Research Center of the Federal Bureau of Minas. A small portion of the pulverized rock is fused with a sodium carbonate-sodium hydroxide flux in a wire loop. The fused mass is dissolved in water, a few drops of quinizarin solution are added, and the solution is viewed under ultraviolet light. A pink-to-orange fluorescence reveals the presence of beryllium in a sample containing as little as 0.013 percent beryllium (0.26 percent beryl). INTRODUCTION New and potential uses for beryllium make necessary a more intensive search for this metal, which is so similar to aluminum in its chemical reactions that it is not separated from aluminum in ordinary chemical analyses. The principal ore mineral of beryllium is beryl, a beryllium-aluminum silicate, which contains only 5 percent beryllium. This mineral is so similar to quartz in appearance that it is not always possible to distinguish one from the other in the field. While the distinction may be made easily with a petrographic microscope, few prospectors have access to such an instrument, and fewer still know how to use it.

Jan 1, 1960

By J. E. Lawver, G. L. Samsel

The success of many mineral dressing processes, including froth flotation and electrical concentration, depends largely on knowledge of physical and chemical structures of the mineral surfaces involved. As a general rule solids have surface layers, usually invisible by optical tests, that differ from the substratum. To the mineral engineer, therefore, a knowledge of the surface structures of minerals is of paramount importance. During the past decade one of the most powerful tools in the study of froth flotation mechanisms has been the use of radioactive tracers, but this technique usually cannot give definite information regarding the chemical changes that may or may not have occurred at the surface. The electron microscope and electron diffraction camera can be particularly useful instruments in surface studies.. An election microscope permits much closer examination of surfaces than can be obtained with a petrographic microscope. In certain cases, it is possible to identify trace quantities formed by chemical reaction between flotation agents and mineral surfaces by the use of a single-crystal, reflection electron diffraction camera. This article describes several instances in which these instruments have been valuable guides in mineral dressing research at International Minerals & Chemical Corp. One of the first applications of these techniques employed by International Minerals was in conjunction with the study of electrical concentration of potash ore. The first reasonably successful separation of potash ore was made by subjecting a sample of the ore to a methanol wash. Subsequent tests using tagged 6C14 methanol showed that only a minute quantity of radioactivity was detectable after the methanol-washed sample had been dried and heated to about 300°F. It was concluded that although some methanol had been held to the surface by adsorption, this could not account for the improved electrification because there was no evidence of methanol selectivity with respect to NaCl or KCl. Consequently there must have been some other change in the surface. Carbon replicas* of the mineral grains were made before and after the methanol wash. The replicas were separated from the minerals by dissolving in water. This extraction replica technique is particularly attractive because the specimen can first be used with the electron microscope to observe the general structure of the surface and can be re-used as a specimen for electron-diffraction studies to identify any solvent insoluble material present on the mineral surface." Fig. 1 shows the general

Jan 1, 1960

By A. W. Sommer, H. H. Kellogg

It is shown that SO3-O2 mixtures react with sphalerite at an appreciable rate ill the temperature range of 361° to 527°C to fornz ZnSO4. The rate of reaction follows a parabolle lax. Oxygen, or O2-SO2 mixtures, have a negligible effect on sphalcrite in the same temperatuee range. PRACTICAL roasting of sphalerite is usually performed at 800°C or higher. The calcine is composed of zinc oxide unless the roaster atmosphere contains relatively large amounts of SO2 and the temperature is held to 800oC or lower, in which case zinc sul-fate may also form. Ong, Wadsworth, and assell' have made a careful kinetic study of sphalerite oxidation under these "normal conditions" and have concluded that the rate of the reaction is controlled by the decomposition of an activated complex adsorbed on the sphalerite surface. They found the rate of oxidation to be small at 700°C. Extrapolation of their data to 400°C would indicate an almost negligible rate at this temperature. In our work sphalerite was reacted with air, mixtures of SO2, O2, and N2, and mixtures of SO3, O2, and N2 in the temperature range 361o to 527OC. Negligible rates of oxidation were found, except for the gas mixtures containing SOs. With this latter gas, the oxidation of finely divided sphalerite was fairly rapid and zinc sulfate was the product. Based on the limited evidence available, the rate of sphalerite oxidation by SO3 is postulated to be controlled by gaseous diffusion through pores or cracks in the zinc-sulfate coating. This evidence for the direct reaction of sphalerite and SO, at low temperature may prove of importance to the understanding of zinc-sulfate formation in the dust-collecting equipment usually associated with zinc roasters. The roaster gas carries off fine dust, much of which may be unreacted sphalerite. The temperature in dust-collecting equipment drops from the roaster temperature (about 800°C) through the range of temperature we studied, to ambient temperature. Such dusts are known to contain far larger amounts of zinc sulfate than the primary calcine. It has been assumed in the past that this sulfate is formed by reaction of ZnO dust with SO3 (or SO, plus 0,) in the partly cooled gases. Our work shows that an alternative possibility exists—the direct reaction of SO3 with ZnS dust. EXPERIMENTAL Reaction rates for sphalerite at 350° to 600°C are relatively small so that it was necessary to use finely divided material with a relatively large surface area in order to obtain measureable amounts of reaction. In the preliminary experiments, pure mineral sphalerite, ground to pass a 325-mesh sieve, and chemically precipitated ZnS (in the form of an impalpable powder) were used. In the quantitative rate experiments the ground mineral sphalerite was processed in an Infrasizer to obtain a product with particle size between 9 and 18 µ. The analysis of this material was 66.7 pct Zn, 0.09 pct Fe, and 32.7 pct S (theoretical sphalerite is 67.1 pct Zn, 32.9 pct S). The sized powder was carefully mixed and divided into l-g samples. The apparatus used for the quantitative rate measurements is shown in Fig. 1. For the preliminary experiments the following change was made: The external catalyst furnace (B, C)* was not used. *Letters refer to Fig._______1 .___- Rather, when catalysis of the SO2 + O2 reaction was desired, the glass beads in basket M were replaced by vanadium-oxide pellets. Procedure—A l-g sample of ZnS was placed on a shallow stainless-steel tray, I, and spread evenly to a depth of about 1mm. The tray was placed in the reaction assembly and the assembly inserted in the cold furnace. The furnace tube was flushed with dry argon and then heated to the desired reaction temperature. The temperature was controlled to ±0.5oC. Gas mixtures (O2 + N2 or O2 + SO2) were prepared from tank gases by means of a mixing device identical to that employed by Darken and Gurry.2 The total flow rate of gas was 205 ml per min to point A of Fig. 1. The accuracy of the individual and

Jan 1, 1960

By W. A. McKinney

A sample of oxidized copper ore from a large deposit located in Pinal County, Ariz., about 50 miles northeast of Tucson, was treated by the Federal Bureau of Mines in a small-scale continuous pilot plant by a procedure which comprised acid curing complemented by water leaching and countercurrent decantation washing in a series of drag classifiers. A feed was prepared by pugging minus 1/4-in, ore with concentrated sulfuric acid and about 10 pct, of eater, followed by curing in batches for about 24 hr. The cured ore was fed continuously to a leach drum, where it was mixed with advance solution from the countercurrent washing system to dissolve the sulfated copper. The pulp was thickened and washed in four Esperanza-type classifiers, using a flocculating agent to obtain rapid settling and thickening. The leached ore pulps thickened satisfactorily in the drag classifiers when about 0.8 lb. of a polyacrylamide flocculant per ton of dry feed was used. Clear overflow liquors were obtained, and classifier rake products containing about 60 pct. solids were produced, As much as 90 lb./hr. of ore was treated in the plant, with a recovery of 60 pct. of the total copper or 80 pct, of the acid-soluble copper when 2 tons of water per ton of feed was used in washing. The acid consumption was 4.3 lb./lb. of copper recovered. On the basis of the maximum feed rate employed and the effective pulp-settling area of the classifiers, a total of 1 sq. ft. of pool area was required per ton of dry feed per day for the thickening and washing operations. The washing efficiency in the test was 95 pct.

Jan 1, 1960

By Raymond L. Carpenter

In connection with its continuing studies of the characteristics of alloys and alloying elements, the Bureau of Mines investigated the crystal structure of fused boron. This report describes how the structure of fused boron was found to be rhombohedral by the powder method for crystal-structure determinations by X-ray diffraction. The determinations of the crystal structure of boron reported in the literature were made on crystals prepared by various methods such as electrolysis, thermal decomposition of a boride, or by hydrogen reduction of boron tribromide. Table 1 summarizes the data found in the literature on the crystal structure of boron. The information shows the following: (1) Three structures have been reported for boron, (2) boron prepared by different processes--or even by varied conditions of a process--produces crystals of different structure, and (3) no information is given on the crystal structure of fused boron.

Jan 1, 1960

By I. L. Feld

This Bureau of Mines report describes the development of a simple method of producing low-phosphorus hematite concentrates from certain submarginal southeastern iron ores. The investigation was undertaken to obtain additional information on the Clinton iron ore outcrops at the southwestern extremity of the Birmingham district of Alabama and to assist in the development of operating techniques that would make it profitable to use the marginal ores of this area for blast-furnace feed. Batch and continuous pilot-plant tests demonstrated that a relatively simple wet scrubbing treatment) followed by a desliming operation to reject argillaceous (clayey) gangue, consistently yielded a marketable granular hematite product. Iron losses were relatively high but could be tolerated in view of the low treatment cost.

Jan 1, 1960

Lloyd W. Ingles, Superintendent, Allen mine, Colorado Fuel and Iron Corporation. Stonewall, Colorado, called the meeting to order at 9:30 a.m. He introduced George C. Trevorrow, Safety Director, Bituminous Coal Operators' Association, Washington, D. C., who spoke on "Recent Developments for Improving Safety in Underground Coal Mines." (Refer to the index for the printed text of this paper.) Following Mr. Trevorrow's paper, James Westfield, U. S. Bureau of Mines, Washington, D. C., spoke briefly to the group or some of the new methods of controlling fire mentioned in Mr. Trevorrow's paper. Mr. Westfield stated that the Foam plug had been used in the Bureau's experimental mine, and was also used in New Mexico, but was not successful in putting out the lire. In a recent fire in Southwest Virginia where 18 men were lost, the foam plug was used after the fire had been burning for about 6 or 7 days. It did have a good effect, but the section had to be finally sealed off. In a fire in Pennsylvania about 2 weeks ago, the foam plug was put into action after about 9 hours. Although the section was finally sealed, managers of the mine credited the foam plug in saving the mine. Mr. Westfield stated that equipment must be at hand when fighting a fire; that time wasted in securing proper equipment may make the difference. Mr. Westfield also stated that as late as 2 months ago, it seemed that a methane monitoring device was as far as 4 or 5 years away. Now it is expected that it may be put in production within the year. Experimental models are in use in Pennsylvania and West Virginia. Mr. Westfield concluded by complimenting Mr. Trevorrow on his excellent paper.

Jan 1, 1960

By P. L. De Bruyn

[According to the Young equation, SG = SL + Coso, the equilibrium contact angle depends on the values of the three interfacial tensions involved. A solute promotes wetting, i. e. a decrease of contact angle if it decreases.LG and/or YSL or if it increases SG. Dewetting, the important step in flotation is, promoted if the solute increases y and/or SL or decreases. Most solutes used for wetting or dewetting are, positively adsorbed at all interfaces involved and consequently according to the Gibbs equation lower the interfacial tensions. Wetting is therefore expected to occur if LG and SL are more affected by the solute than SG. Dewetting on the other, hand demands a greater decrease of SG than that of SL (and of LG). See P. L. de Bruyn, J. Th. G. Overbeek and B. Schuhmann, Jr., Mining Engineering (1954) P. 519.]

Jan 1, 1960

By W. J. Kroll

Jan 1, 1960

By L. F. Porter, G. J. Dienes

The effect of netltron irracliation on mart ensite transformation in the iron-nickel system was studied by means of electrical resistance and magnetic induction measuremertts. Irradiation lowers the M8 temperature of the allay, causes changes in the electrical and magnetic properties of the high-temperature phase which indicate either an accelemtion of phase separation or a clustering of nickel, and enhances strain recovery on specimens partially transformed to martensite prior to irradiation. Possible mechanisms to account for the effects; are discussed. 1 HERE is a good deal of evidence to indicate that neutron irradiation is capable of affecting phase changes in metals and alloys. While the mechanism of the effect often is not well understood, such studies hold promise of improving our understanding not only of irradiation damage but also of the phase changes involved. To date systematic and detailed investigations have been made of the influence of nuclear radiation on order-disorder transformations in the copper-gold, nickel-manganese, and copper-zinc system, and on precipitation reactions in the copper-iron, nickel-beryllium, and copper-beryllium system.' These solid-state reactions are diffusion controlled and the results can be explained largely on the basis of enhanced diffusion due to the presence of irradiation produced vacancies. Reversion of low-temperature eutectoid phases to the high-temperature phase has been observed in the fissionable uranium-molybdenum and uranium-niobium systems.2 Here it is necessary and logical to postulate a displacement spike mechanism to account for the effect. The only case of irradiation induced diffusionless transformation in metals is the allo-tropic transformation of p to a tin reported by Flee-man and Dienes. 3 They found that neutron irradiation markedly decreases the incubation time for transformation, but the mechanisnl is not well understood. Another diffusionless transformation which one might expect to be influenced by neutron irradiation is the martensite transformation. This transformation is known to be sensitive to strain, structural hardening, and the presence of imperfections.6,7 Since the transformation is diffusionless, one also

Jan 1, 1960

By J. W. Whitlow, P. K. Theobald, W. C. Overstreet

Monazite placers in a region of the Carolinas ex- in 1951-1954 by the USGS are estimated to contain at least 53,000 short tons of thorium and 4600 short tons of uranium. None of these deposits is being mined. The 5200-sq mile area investigated extends northeast along the western Piedmont from the Savannah River in South Carolina to the Catawba River in North Carolina. Much of the region is 700 to 1100 ft above sea level. Gentle hills and broad interfluves give a local relief of 100 to 200 ft. This increases to 1700 ft at the west margin of the area where the east flank of the Blue Ridge is approached in South Carolina and the South Mts. are entered in North Carolina. This report is restricted to placers in the Piedmont. Monazite deposits in the Blue Ridge and coastal plain were not covered by the investigation. Monazite Mining in the Carolina Piedmont: Discovered in 1879 by W. E. Hidden,' the monazite placers in the Carolina Piedmont were first mined in 1886. The area was a major world source for thorium and the lanthanides until 1895, when Brazilian monazite entered the trade. Total output from the Carolina Piedmont has been nearly 5500 tons of monazite,2 but the placers have been idle since 1911, except for 48 tons produced between 1915 and 1917. Monazite mining was revived in the Carolinas in 1954 when a dredge operated by the Heavy Minerals CO. opened a fluviatile placer along Horse Creek in the coastal plain near Aiken, S. C. Geology and Mineralogy: Two recent papers",' have described the geology of the monazite placer district in the Piedmont between the Savannah and Catawba rivers; the general geology of the region has been reviewed by P. B. King.' These reports show that the placers are in locally derived alluvial sediments that cover the floors of shallow, narrow valleys in an area underlain by monazite-

Jan 1, 1960

By John Drew Ridge

Tables showing world trade in metallic mineral raw materials during the years 1953 through 1957 have been prepared for the following twenty-one commodities: alumina, aluminum, bauxite, chromite, copper concentrates, partly refined and fully refined copper metal, iron ore, pig iron, iron and steel (simple shapes), lead concentrates, lead metal, manganese ore, mercury metal, nickel ore, concentrates, and matte, nickel metal, raw pyrites, sintered pyrites, tin concentrates, tin metal, zinc concentrates, and zinc metal. In each instance, the amounts given by the importing country were used except when statistics from the importing nation were lacking, incomplete, or misleading. To show the considerable divergence between importing and exporting country totals for the same years, the complete mercury table is given and, in parallel columns, shows the comparable tonnages of importers and exporters. Tables for the other twenty commodities are presented in summary form. The data of the concentrate tables are used with those of the corresponding metals as a basis for a discussion of trade in concentrates versus trade in metals. The data of all twenty-one tables provide the basis for testing the thirteen rules governing international trade in metal raw materials which I first published in Mining Engineering for July 1955. Because the 1953 through 1957 data are far more complete and considerably more extensive than those on which the 1955 rules were based, it was found possible to deduce five additional rules and to modify three of the original thirteen appreciably. The full text of the eighteen rules is given.

Jan 1, 1960

By J. B. Newkirk

ABOUT twenty-seven years ago W. bergl discovered that interesting detail could be seen in an X-ray diffraction spot made with a rock-salt crystal if the recording photographic film were held very close to the reflecting crystal. He also showed that much of this detail could be explained in terms of the deformation structure of the specimen. In the same year, 1931, Fox and parr2 reported that X-ray reflections from a quartz crystal were much more intense while the crystal was undergoing piezoelectric oscillation than when it was at rest. This observation was soon confirmed (and explained in terms of X-ray extinction) by Barrett3 in the United States and by Nishikawa et a1.,4 in Japan. During the next few years Barrett refined Berg's method for making X-ray diffraction micrographs and applied it to the study of metallic crystals. He reported this work in the 1945 annual lecture of the AIME.5 Since 1945 relatively little use has been made of the Berg-Barrett (B-B) method for making diffraction micrographs, though considerable interest in investigating subcrystal structures by other methods has developed. Some of these methods depend upon evaporation6 or chemical etching7 and, therefore, suffer from the occasional intrusion of subtle artifacts such as those recently reported by Hooker for leada and Welsh for aluminum.9 Other methods require the introduction of foreign elements which "decorate" the substructure in some way, thereby rendering it detectable by direct" or indirect1'. visual examination. Still others depend upon complex and often highly questionable analyses of X-ray diffraction line profiles. There have also been a number of related X-ray techniques, such as the Lambot,12 Schulz13 and Merlini and Guinier,14 which have proved to be quite useful for specific applications. Some of these methods give a picture of the substructure which is more or less directly related to the shape and the topography of the specimen. The Berg-Barrett method carries this desirable feature to the limit. Closely related to the B-B method are three photographic X-ray techniques recently described by Lang.15 These methods give beautiful pictures of the internal structure of crystals but are limited by the facts that the required apparatus is rather complex, exposure times are long, and the specimen crystals must be thin. An experimental appraisal which I have recently made of the original B-B method has shown that this simple technique is not only inexpensive and convenient, but can give more information than was apparently realized by its inventors. For example, first-order subgrains in iron-silicon crystals were clearly delineated and their relative orientation subject to description. Also defect structures could be seen within the subgrains and in some materials slip bands could be clearly seen with respect to the topography of the rest of the specimen. This much had already been described by Barrett. However, in the present study it was found that the actual sites of individual dislocations which emerge upon the crystal surface could be located. Furthermore, by a simple procedure, the direction (but not sign) of the dislocation Burgers' vector could be defined as well.

Jan 1, 1960

Map

Jan 1, 1960

By D. J. Mack, R. E. Reiswig

Six examples of the peritectoid transformation were selected from the literature and studied by the method of isothermal transformation. The kinetics and mechanisms of five of the examples are presented as TTT diagrams and photomicrographs. The exist-enc- of a peritectoid in the sixth case is doubtful. ALTHOUGH the peritectoid transformation per se has been known for many years, no precise published data exist concerning the kinetics or mechanisms involved in transformations of this type, except for the brief treatment by Rhines, et al. 1,10 Bearing in mind the fact that investigations of recent years are uncovering more and more peritectoids and suspected peritectoids, a thorough study of the well-established peritectoids appeared to be in order. It was for this reason that a study of the kinetics and morphological mechanisms of six binary peritectoids was undertaken. The six peritectoids selected from the literature for study were those reported at 7.02 wt pct Al-Ag, 26.0 wt pct Sb-Cu, 30.5 wt pct Sb-Cu, 32.3 wt pct Sn-Cu, 8.35 wt pct Si-Cu, and 21.2 wt pct Al-Cu. These selections were based on availability and purity of components, ease of preparation and heat-treatment, and estimated reliability of the available equilibrium diagrams in the regions of interest. EXPERIMENTAL PROCEDURE The alloys used in this investigation were induction melted in electrode-grade graphite and chill-cast in cast-iron split molds. In all cases, the alloys were so brittle that they could easily be broken into samples weighing 1 or 2 g. Chemical analyses showed that the alloys used were close to the respective peritectoid compositions reported in the literature and that the impurity levels were low in all cases. Metallographic examination showed uniform distributions of phases in all samples, indicating uniformity of composition in the samples studied. Isothermal transformation studies were carried out in fused-salt media, using the familiar inter-rupted-quench method. Uniformity of temperature in the salt baths was maintained by continuous stirring with a stainless-steel agitator. On the basis of actual observations of the temperature fluctuations, the estimated temperature control was + 10C for the Ag-Al and Cu-Sb alloys and ±30C for the Cu-Sn, Cu-Si, and Cu-Al alloys. The accuracy of all temperature measurements was estimated to be ±1°C. It was found necessary to mount metallographic specimens of the Ag-Al alloy in cold-curing methyl methacrylate, since the temperatures encountered in mounting in bakelite or lucite caused an appreciable degree of transformation to the ß phase. For the other alloys, wood-flour-filled bakelite mounts were used to avoid extraneous X-ray diffraction lines during the later examination of the metallographic specimens on a Norelco Geiger-counter d if f r ac tomete r. In the X-ray diffraction procedure, agreement between the published diffraction patterns and those obtained in this study was good. This was particularly important for phase identification, since the literature contained little in the way of micrograph description in some cases. Etching of the silver-aluminum alloy for metallographic examination was done by swabbing with either of the following reagents: 1) 10 g CrO3, 1 g (NH4), SO2, 0.5 g NH4NO3, 100 ml H2O, or 2) 10 ml NH4OH, 1 ml 20 pct KOH, 4 ml 3 pct H2O2, 5 ml H2O. The other alloys were etched with the usual bichromate etchant: 2 g K2Cr2O7, 1.5 g NaC1, 8 ml conc. H2SO4, 100 ml H20 (swabbed vigorously). EXPERIMENTAL RESULTS A) The Ag-Al peritectoid at 7.02 wt pct Al— The phase equilibrium involved in this peritectoid is shown in Fig. I.2 The phase boundaries in the vicinity of the peritectoid were most comprehensively established by Hume-Rothery, et al,3 who placed the equilibrium temperature at 448 °C and the equilibrium compositions of the a ß' and y phases at 6.11, 7.02, and 7.24 wt pct Al, respective The alloy used in this study analyzed4 6.95 wt pct A making it slightly hypoperitectoid according to the accepted equilibrium diagram. The rate of the transformation a+ y — ß' varies rapidly with degree of undercooling below the equilibrium temperature, passing through a maximum in the vicinity of 350°C. Thus the TTT dia-

Jan 1, 1960

By A. G. Buyers, J. Chilton, W. E. McKee

STUDIES in the high-temperature separations chemistry of thorium-uranium fuels are complicated by the corrosive nature of these molten metal systems at 1700°C. Separations research pointed toward the removal of fission products from irradiated alloys has included a frozen salt-bed technique which minimizes container reaction with molten metal. The procedure consists of high-frequency induction melting of the metal sample which is supported by a vertical column of unmelted salt. The molten alloy melts its immediate salt environment and as it slowly falls down through the column, many of the fission-product poisons are transferred into the fused salt environment. The molten salt-metal zone is encompassed at all times by unmelted salt, preventing container contact. EXPERIMENTAL Experimental methods were separated into three parts: salt-bed preparation, melting, and analytical evaluation. A) Bed Preparation—The procedure for casting calcium-fluoride briquettes was to compress the powdered salt at 5,000 to 10,000 psi and place this compact in a graphite crucible. This assembly was inserted into a vacuum system and surrounded by an alumina crucible as well as molybdenum, tantalum, or stainless-steel foil thermal-radiation shields. The pressure was reduced and the crucible heated under vacuum to about 800°C with the fore pump operating. Argon was then admitted to about 0.8 atm and heating continued until the CaF2 had melted 5 min at the melting point seemed satisfactory). Apparatus used included a 1-in. graphite crucible with 1/8-in. walls, 1-in. ID in a 2-in. induction coil, and a 6-kw Ajax high-frequency converter. B) Melting—Calcium-fluoride briquettes, 1 in. in diam and 1/2 to 1 in. thick, were prepared and vertically stacked to obtain the desired column length. An irradiated alloy sample (nut = 10") was placed on top of the salt column and the assembly was connected to the vacuum system. After evacuation of 5 to 10 , purified argon was admitted and the system flushed twice. The final argon pressure was about 0.8 atm. The sample was heated by induction at a power of about 6.5 kw. It then melted its way down through the salt and freely dropped into a small alumina crucible. The molten metal is followed during its downward course by the induction coil which is mounted upon a power-driven machine-threaded shaft. Experimental conditions used in the foregoing work

Jan 1, 1960

By S. C. Lindsay, D. J. I. Evans

With each year that passes hydrometallurgical processes are being more widely used to recover base metals from ores and concentrates. Generally these processes involve liquid-solid separation of metal-bearing liquors from barren residues. This may be done by countercurrent decantation, thickening and filtration, or filtration or centrifuging only. Choice of method is governed by chemical and physical characteristics of the pulps; cost of labor, power, materials, and waste disposal; and even by the amount of capital available when building plans are under way. Since all these controlling factors change with time and location and with technological advances, the separation method must be re-evaluated when new plants or expansion programs are contemplated. At the Sherritt Gordon refinery in Fort Saskatchewan, Alberta, an ammonia pressure leaching process recovers nickel, copper, and cobalt from the nickel concentrate produced at Lynn Lake, Manitoba.' Pregnant liquors are separated from the barren leach residues in a thickener-filter liquid-solids circuit. The decision to use this type of separation was based on a summation of economic factors during the pilot plant and design stages. Although countercurrent decantation was not incorporated in the refinery flowsheet, the problems solved in thickening the leach residues and the experience gained in operating the commercial plant are pertinent to countercurrent decantation, particularly where it is applied to slow-settling leach slurries or slurries having a relatively high vapor pressure of a valuable, obnoxious, or poisonous vapor.

Jan 1, 1960