Search Documents

By J. F. Haseman, J. E. Davenport

IN the brown rock phosphate fields of Tennessee there are large deposits of phosphate matrix in which quartz is a major constituent of the gangue, and which cannot be beneficiated by the conventional washing process to yield a concentrate of suitable grade for use in the electric furnace. A huge tonnage of high-grade phosphate concentrate is produced in the Florida pebble district from low-grade siliceous feed. However, the characteristics of the low-grade siliceous Tennessee ore are such that flotation under the conditions employed in treating the Florida ore1-2 results in inadequate beneficiation. INVESTIGATION OF FLOTATION METHODS Flotation has been used in Tennessee primarily to produce a concentrate of premium grade by moderate enrichment of a marketable grade of phosphate.3,4 A secondary use was to increase the recovery of phosphate from the fines (down to approximately 200 mesh) from medium-grade ores with a concomitant moderate increase in over-all grade.3,5 It was considered desirable to investigate methods of improving the grade of washed products from low-grade siliceous Tennessee ore when these products were substantially below the requirements for use in the electric furnace. The present paper describes the results of a laboratory-scale study of factors that affect the beneficiation of such siliceous phosphate ore by flotation. The primary objective of the investigation was to ascertain the conditions under which the ore could be made to yield a concentrate suitable for reduction in the electric furnace. It was assumed that a phosphate concentrate for electrothermal reduction should contain at least 26 pct P205 and should have a weight ratio of silica to lime of not more than 0.80. Since a concentrate of moderate grade can be used in the electric furnace, and since, as Grissom4 has shown in detail, the ore will not bear the cost of expensive treatment, the study of collectors was limited to the relatively inexpensive fatty acids. A secondary objective was to determine whether a portion of the phosphate could be recovered in a grade suitable for treatment with phosphoric acid to produce 45 pct superphosphate. The ore consisted of variably cemented sand interlayered with clay. The sand layers were composed of grains of quartz, phosphate, and clay embedded in a matrix of clay and phosphate. Some clay was finely disseminated in the phosphate grains. Little massive high-grade phosphate was present. The material used in the flotation tests was a washed sand that had been separated from the ore in a bowl classifier at the TVA phosphate-washing plant. The percentage composition of the sand was as follows: P205, 20; Si02, 40; CaO, 29; Fe203, 2; A1203, 3; F, 2.3. The particle-

Jan 1, 1947

By H. W. Young

DEVELOPMENT of high-tension outdoor substations during the past few years has been due primarily to economic reasons. The demand for power in small communities could not be met with the conventional and 1 FIG. 1.-33,000-VOLT STEP-UP OUTDOOR AIR-BREAK SWITCH AND SUBSTATION INSTALLATION OUTSIDE OF A POWERHOUSE GENERATING AT 2300 VOLTS STEPPING UP TO 33,000. TWENTY-ONE COAL MINES ARE SUPPLIED FROM LINES LEADING FROM THIS INSTALLATION. comparatively expensive indoor types unless the rate for service was materially increased. That the various problems incident to development have been solved successfully, it is only necessary to point to the

Jan 9, 1919

By J. F Haseman, J. E. Davenport

In the brown rock phosphate fields of Tennessee there are large deposits of phosphate matrix in which quartz is a major constituent of the gangue, and which cannot be beneficiated by the conventional washing process to yield a concentrate of suitable grade for use in the electric furnace. A huge tonnage of high-grade phosphate concentrate is produced in the Florida pebble district from low-grade siliceous feed. However, the characteristics of the low-grade siliceous Tennessee ore are such that flotation under the conditions employed in treating the Florida ore1,2 results in inadequate beneficiation. Investigation of Flotation Methods Flotation has been used in 'Tennessee primarily to produce a concentrate of premium grade by moderate enrichment of a marketable grade of phosphate. 3,4 A secondary use was to increase the recovery of phosphate from the fines (down to approximately 200 mesh) from medium-grade ores with a concomitant moderate increase in over all grade.3,5 It was considered desirable to investigate methods of improving the grade of washed products from low-grade siliceous Tennessee ore when these products were substantially below the requirements for use in the electric furnace. The present paper describes the results of a laboratory-scale study of factors that affect the beneficiation of such siliceous phosphate ore by flotation. The primary objective of the investigation was to ascertain the conditions under which the ore could be made to yield a concentrate suitable for reduction in the electric furnace. It was assumed that a phosphate concentrate for electrothermal reduction should contain at least 26 pct P2O5 and should have a weight ratio of silica to lime of not more than 0.80. Since a concentrate of moderate grade can be used in the electric furnace, and since, as Grissom4 has shown in detail, the ore will not bear the cost of expensive treatment, the study of collectors was limited to the relatively inexpensive fatty acids. A secondary objective was to determine whether a portion of the phosphate could be recovered in a grade suitable for treatment with phosphoric acid to produce 45 pct superphosphate. The ore consisted of variably cemented sand interlayered with clay. The sand layers were composed of grains of quartz, phosphate, and clay embedded in a matrix of clay and phosphate. Some clay was finely disseminated in the phosphate grains. Little massive high-grade phosphate was present. The material used in the flotation tests was a washed sand that had been separated from the ore in a bowl classifier at the TVA phosphate-washing plant. The percentage composition of the sand was as follows: P2O5, 20; SiO2, 40; CaO, 29; Fe2O3, 2; Al2O3, 3; F, 2.3. The particle-

Jan 1, 1948

By J. F. Haseman, J. E. Davenport

In the brown rock phosphate fields of Tennessee there are large deposits of phosphate matrix in which quartz is a major constituent of the gangue, and which cannot be beneficiated by the conventional washing process to yield a concentrate of suitable grade for use in the electric furnace. A huge tonnage of high-grade phosphate concentrate is produced in the Florida pebble district from low-grade siliceous feed. However, the characteristics of the low-grade siliceous Tennessee ore are such that flotation under the conditions employed in treating the Florida ore1,2 results in inadequate beneficiation. Investigation of Flotation Methods Flotation has been used in 'Tennessee primarily to produce a concentrate of premium grade by moderate enrichment of a marketable grade of phosphate. 3,4 A secondary use was to increase the recovery of phosphate from the fines (down to approximately 200 mesh) from medium-grade ores with a concomitant moderate increase in over all grade.3,5 It was considered desirable to investigate methods of improving the grade of washed products from low-grade siliceous Tennessee ore when these products were substantially below the requirements for use in the electric furnace. The present paper describes the results of a laboratory-scale study of factors that affect the beneficiation of such siliceous phosphate ore by flotation. The primary objective of the investigation was to ascertain the conditions under which the ore could be made to yield a concentrate suitable for reduction in the electric furnace. It was assumed that a phosphate concentrate for electrothermal reduction should contain at least 26 pct P2O5 and should have a weight ratio of silica to lime of not more than 0.80. Since a concentrate of moderate grade can be used in the electric furnace, and since, as Grissom4 has shown in detail, the ore will not bear the cost of expensive treatment, the study of collectors was limited to the relatively inexpensive fatty acids. A secondary objective was to determine whether a portion of the phosphate could be recovered in a grade suitable for treatment with phosphoric acid to produce 45 pct superphosphate. The ore consisted of variably cemented sand interlayered with clay. The sand layers were composed of grains of quartz, phosphate, and clay embedded in a matrix of clay and phosphate. Some clay was finely disseminated in the phosphate grains. Little massive high-grade phosphate was present. The material used in the flotation tests was a washed sand that had been separated from the ore in a bowl classifier at the TVA phosphate-washing plant. The percentage composition of the sand was as follows: P2O5, 20; SiO2, 40; CaO, 29; Fe2O3, 2; Al2O3, 3; F, 2.3. The particle-

Jan 1, 1948

By Helmer Heldstrom

Gravity surveying with the torsion balance or the pendulum for ore prospecting purposes has generally not been considered practical or even possible. It is the intention of this paper to show that a fast and sensitive gravimeter can be very useful in ore prospecting, as an auxiliary to the electrical and magnetic instruments. A number of gravimeters have been constructed and put in practical use in the last seven or eight years; for instance, by Ising, Lejay-Holweck, Haalck, Hartley, Thyssen, Noergaard, the Humble Oil and Refining Co. and the Gulf Production Co. Their main application, apart from their use for geodetic surveys, has been for structure mapping in oil prospecting. There is no record that any of them have been used for ore prospecting. About the middle of 1934 the Boliden Mining Co., in Sweden, began experiments in constructing a static gravity meter sensitive enough for ore prospecting. Calculations and considerations that will be discussed later in this paper showed that this would necessitate an accuracy in the measurements of 0.1 milligal—roughly, one ten-millionth part of the total force of gravity. The first successful practical field tests of the instrument were made in January 1936. About the middle of 1937 the Boliden gravimeter was perfected. Ore prospecting with this instrument is now regular practice in Sweden, especially for the testing of indications given by geoelectric and magnetic methods. Gravity Anomalies that May Be Expected from Ore Bodies According to Newton's law, a mass M attracts the unit mass in a distance r with the force , GM where G = the gravitational constant = 6.68 . 10-8 c.g.s units. In the c.g.s., or centimeter-gram-second, system the force of attraction is expressed in the unit "dyne," which has the physical dimension c.g.s.-2 and denotes the force needed to accelerate the unit mass in one second to

Jan 1, 1940

By Helmer Heldstrom

Gravity surveying with the torsion balance or the pendulum for ore prospecting purposes has generally not been considered practical or even possible. It is the intention of this paper to show that a fast and sensitive gravimeter can be very useful in ore prospecting, as an auxiliary to the electrical and magnetic instruments. A number of gravimeters have been constructed and put in practical use in the last seven or eight years; for instance, by Ising, Lejay-Holweck, Haalck, Hartley, Thyssen, Noergaard, the Humble Oil and Refining Co. and the Gulf Production Co. Their main application, apart from their use for geodetic surveys, has been for structure mapping in oil prospecting. There is no record that any of them have been used for ore prospecting. About the middle of 1934 the Boliden Mining Co., in Sweden, began experiments in constructing a static gravity meter sensitive enough for ore prospecting. Calculations and considerations that will be discussed later in this paper showed that this would necessitate an accuracy in the measurements of 0.1 milligal—roughly, one ten-millionth part of the total force of gravity. The first successful practical field tests of the instrument were made in January 1936. About the middle of 1937 the Boliden gravimeter was perfected. Ore prospecting with this instrument is now regular practice in Sweden, especially for the testing of indications given by geoelectric and magnetic methods. Gravity Anomalies that May Be Expected from Ore Bodies According to Newton's law, a mass M attracts the unit mass in a distance r with the force , GM where G = the gravitational constant = 6.68 . 10-8 c.g.s units. In the c.g.s., or centimeter-gram-second, system the force of attraction is expressed in the unit "dyne," which has the physical dimension c.g.s.-2 and denotes the force needed to accelerate the unit mass in one second to

Jan 1, 1940

By William A. Mitchell

AN X-ray diffraction pattern for "calcined cold precipitated ferric oxide" is reproduced dia-grammatically along with data for other iron oxides by R. C. Mackenzie.1' This pattern, which shows spacings higher than those for any other form of iron oxide, was obtained from material prepared and photographed at several different times over a period of weeks, but later attempts to reproduce the results were unsuccessful, the pattern of hematite being obtained every time.2 In an attempt to solve this problem, the original photographs showing the strange diffraction pattern were examined and a marked similarity to the hematite pattern was noticed, suggesting that the pattern was in fact due to hematite but corresponded to a shorter wavelength of X-rays than the Cu Ka which was assumed to have .been used. The eight strongest lines were provisionally identified with the strongest hematite lines and, by means of the corresponding hematite spacings, the X-ray wavelength was calculated for each line. This gave an almost constant value, with the exception of the innermost line which was somewhat diffuse, and confirmed the presence of hematite. The value obtained, 0.703 ± 0.015Å, corresponds to the molybdenum Ka wavelength. The X-ray tube used was a four-filament demountable tube with a copper target. Other photographs, mostly of soil clays, taken during the same period gave normal patterns of Cu Ka radiation with one exception. This was a calcined soil clay with a high iron content and also showed Mo Ka lines of the hematite structure. The explanation is almost certainly that the copper target was contaminated with molybdenum, but it is not known how this occurred. Specimens of alumino-silicates gave their normal Cu Ka pattern, but as the K absorption edge of iron is a little longer than the Cu Ka wavelength, specimens with a high iron content greatly reduced the intensity of the Cu Ka diffraction lines relative to that of the lines due to the shorter Mo Ka wavelength. The formation of hematite on calcining cold precipitated hydrated ferric oxide3 is thus confirmed. References R. C. Mackenzie: Investigations on Cold-precipi-tated Hydrated Ferric Oxide and its Origin in Clays. Problems of Clay and Laterite Genesis, p. 69, Fig. 4, F. AIME Symposium, St. Louis, Mo. Feb. 19-22, 1951. Published 1952. 'R. C. Mackenzie: Ref. 1. Note added on proof. V. C. Hansen and L. T. Brownmiller: Equilibrium Studies on Alumina and Ferric Oxide and on Combinations of These with Magnesia and Calcium Oxide. American Journal of Science (1928) 5, No. 15, pp. 225-242.

Jan 1, 1954

By T. D. Tiemann

The chemical and mineralogical composition of Caribbean bauxite ores are described. Extraction of alumina by several processes from both Haiti and Jamaica bauxites is discussed and data presented. IMMENSE deposits of bauxite occur in the Caribbean islands of Hispaniola and Jamaica in the high plateau lands and have been excellently described by 0. C. Schmedeman.' The bauxite occurs as deposits in catchments or etched depressions in Tertiary limestone believed to have been deposited in the Eocene and Oligocene periods.' In appearance both the Haiti and Jamaica bauxites resemble a relatively high iron clay and have indeed been mistaken for such.' They are very soft and friable and disperse readily on vigorous agitation in water. The color range in general is light brown to red. Chemically, the outstanding characteristic of the bauxites is the low silica and high ferric oxide content. The extremely low silica makes them particularly valuable for the production of alumina in the Bayer plant since silica is responsible for the loss of both alumina and soda chemically combined as XNa,OYSiO2,ZAl2O2. The ferric oxide, only traces of ferrous iron are present, offers no interference in the production of high grade alumina. Typical oxide analyses of three types of ore are given in Table I2 and a list of the elements occurring in spectrographic quantities in Table 11." The size of the individual particles in the ore makes successful petrographic examination extremely difficult. The ores contain some relatively coarse grains of heavy minerals such as ilmenite, magnetite, and rutile, but other than occasional crystals of a few microns, the greater portion of the minerals are submicroscopic in size and approach colloidal dimensions. The mineralogic composition of the ores has been investigated by X-ray and differential thermal analysis.' These investigations indicate that the predominant mineral phases present are gibbsite (A1203.3H2O), boehmite (Al2O3.H2O), hematite (Fe2O3), and goethite (Fe2O3-H2O). There is no evidence of the occurrence of diaspore (Al2O3.H2O) in either the Haiti or Jamaica ores, but some type of "amorphous" alumina may be present in some of the bauxites of Jamaica." The temperature stability regions in the alumina-water system have been investigated and are given in recent literature. In the temperature range where the hydrated forms are stable, as determined by hydrothermal bomb methods," ibbsite is the stable phase to 155°C (311°F), boehmite from 155°C (311°F) to 280°C (536oF), and diaspore from 280°C (536°F) to 450°C (842°F). Although quite similar in many characteristics, the Haiti and Jamaica ore show a divergence in mineralogic composition that is reflected in the extractability of the alumina described in later paragraphs. Two principal differences occur in mineralogic composition. The iron-bearing mineral in the Haiti ores is predominantly hematite, while in the Jamaica ores goethite is predominant.4 Directly related to the extraction of alumina are the two minerals, gibbsite and boehmite. Boehmite is relatively high in the Haiti ores and in some of the less soluble Jamaica ores, while gibbsite predominates in the ores in Jamaica amenable to the American Bayer process of extraction. Pedersen and Related Processes In general, all processes for the extraction of alumina involving sintering or fusion of bauxite ores with limestone, soda ash, or a combination of limestone and soda ash followed by leaching, are based on the formation of alumina compounds that. yield alumina soluble in the subsequent leach. The principal idealized reactions in respect to alumina and silica for the three types of processes are as follows: Soda Ash Sinter: A12O3 + Na2CO3 = Na2O-Al2O, + CO2 SiO2 + Na2CO3 = Na2O . SiO2 + CO2 A12O2 + SiO2 + Na2CO3 = Na2O.Al2O8. SiO2 + CO2 Leach (with excess water): H2O + Na2O-A12O3 = 2 NaOH + A12O3 (insolution) H2O + Na2O-SiO2 = 2 NaOH + SiO2 (in solution) Soda Ash— Limestone Sinter: Na2CO2 + A12O3 = Na2O.A1203 + CO2 2CaCO3 + SiO2 = 2CaO . SiO2 + 2CO2 Leach (with excess water): Na2O' A1208 + H2O = 2NaOH + A13O3 (in solution) These latter reactions are the basis of the sinter process currently used for the recovery of soda and

Jan 1, 1952

By S. Beatty

RECENT experimental results' on the superconductive properties of vanadium indicate that the magnetic behavior of the metal is greatly affected by internal strains caused by mechanical work, and particularly by oxygen and nitrogen impurities. These result in an increase in the hardness of the metal such that metallurgists' have used hardness as a measure of the impurities. An increase in the impurities should also be reflected in a change of lattice parameter with increasing impurity content. The lattice parameter of vanadium prepared by the thermal decomposition of the iodide has been determined by two workers. Neuburger3 obtained a value of a, =3.0338 ± 0.0003A for the body-centered cubic lattice by means of the powder method. The work of Katelaar is referred to by van Arkel4 in which a value of a0 = 3.025 is given. Four samples were used for this investigation. Sample A, the vanadium of the highest purity in the group, was obtained by means of the thermal decomposition of vanadium diiodide and deposited on a 3 mil diam tungsten filament in the form of crystals. The second sample, labeled B, was obtained by the calcium reduction of the pentaoxide at a sufficiently high temperature to give a melt. A third sample, C, was obtained in the same manner as B but remelted in a pure argon atmosphere. The last sample, D, was prepared by the calcium reduction method and the fine powdered vanadium was then sintered by means of applied heat and pressure. Samples A, B, and C were thus essentially free of mechanical strain in their preparation. Sample D was annealed in a high vacuum at 800°C. The samples were prepared for X-ray diffraction analysis such that all additional strain by cold work or by contamination with oxygen and nitrogen was kept at a minimum. Powder obtained from filings was deemed unsuitable since this would require annealing to get rid of the cold work. A heat treatment up to 1000°C at 10-6 m pressure might still increase the impurity content by means of adsorbed oxygen from residual gas in the vacuum chamber. The most satisfactory samples were prepared for back-reflection film techniques. Samples were cut to size, etched with hydrobromic acid, and mounted in Bakelite. They were then lightly polished on 3-0 paper and lightly etched. Chemical and Hardness Analysis of Samples Spectrographic analyses were made of the four samples and indicated similar metallic impurities for the group. The major metallic impurity in each sample was iron, which was less than 0.01 pct. The sum of the other metallic impurities was approximately 0.1 pct. The carbon content was assumed low by virtue of the methods of sample preparation. The principal impurity difference between the samples was in the oxygen and nitrogen content.

Jan 1, 1953

By William L. Fink, E. H. Dix, L. A. Willey

The results of a preliminary investigation of the aluminum-iron-manganese system showed that small amounts of iron (0.10 per cent) substantially reduce the solid solubility of manganese in aluminum. This is clearly shown in the photomicrographs of three alloys, Figs. 1 to 3. Fig. 1, of an alloy containing 1.04 per cent manganese after a heat treatment at 626° C. for 45 hr., shows only solid solution. This alloy contained less than 0.008 per cent iron. Fig. 2 shows the abundance of a constituent (which undoubtedly contains aluminum, manganese and iron) in an alloy containing 1.00 per cent manganese and 0.11 percent iron after a solution heat treatment at 625" C. for 63 hr. For comparison, Fig. 3 is included to show the relatively small amount of constituent (FeA13) in a similarly heat-treated aluminum alloy containing 0.10 per cent iron but no manganese. These data necessitated a reconsideration of the binary aluminum-manganese diagram that was previously presented,' inasmuch as the alloys used in that work contained from 0.02 to 0.05 per cent iron. This paper is the fourteenth of a series from the Research Laboratories of the Aluminum Company of America reporting the results of investigations of equilibrium relations in aluminum-base alloys of high purity. The purpose was to determine the phase relations in aluminum with aluminum-manganese alloys containing the smallest amount of iron that could be realized with the purest material available at the present time (less than 0.01 per cent iron). Since the previous publication from these laboratories, five investigations of the aluminum-manganese system have been reported. Krings and Ostmannz assigned the formula MnA14 to the compound at the aluminum end of the syst,em, and found a eutectic between this compound and aluminum at 649" C. and 3 per cent manganese.

Jan 1, 1933

By Thomas E. Wayland

AN isopachous map is one on which lines connect points of equal thickness of a given unit. This type of map is used by the Florida Phosphate Project of the U. S. Geological Survey to represent the economic phosphate deposits known as matrix and the waste material, or overburden, that overlies the matrix. The top of the bed on which the phosphate was deposited is known as the basement and a subsurface contour map of this old buried erosion surface is known as a basement map. Recent experiments have been made in preparing maps that show tonnages and grades of the phosphate content of the matrix.

Jan 11, 1951

By L. O. Howard

Much work has been done recently on the lead-antimony system' in connection with lead-rich alloys of commercial importance containing less than 20 per cent. antimony. Dean, Zickrick and Nix have called attention to the perpetuation in the literature of several erroneous data, such as a eutectic temperature of 228° C. at 12.5 per cent. antimony, instead of 247° at 13 per cent. The series is given as a classic example of a straight eutectiferous series in such late books as those of Heyn and Grossmann,2 Jeffries and Archer,3 Guillet and Portevin,4 Pulsifer,5 Rosenhain,6 and Liddell,7 as well as the somewhat earlier works of Hofman (1918), Wang (1909), and Williams (1920). The work of Dean has definitely shown a solid solution of antimony in lead at about 2.5 per cent. antimony. While lecturing to a class in general metallurgy at the University of Idaho, the writer had the students prepare a series of lead-antimony alloys for the purpose of illustrating methods of thermal analysis. Proper proportions of powdered antimony (sold as C.P.) and. test lead were mixed and melted in graphite crucibles under a reducing cover. Cooling

Jan 1, 1928

By Peter G. Groer

Several methods1-3 are being used to determine the WL and individual Rn-daughter concentrations in uranium mine atmospheres. The best of these methods is the one given in Ref. 3. According to this method, the WL and the Rn-daughter concentrations are determined from the total a-counts observed during three consecutive time intervals. Its only disadvantage lies in the fact that rather involved calculations are necessary to convert the observed counts into WL or pCi/l (picocuries per liter). There are, however, counting intervals that give simple weighting coefficients for the observed counts. This fact makes it possible to convert from a-counts to WL or pCi/l with the aid of a graph. After some trial runs on a computer the following equations emerged as the basis for the most practical procedure: [ ] NA, N.., and & stand for the number of RaA, RaB, and RaC atoms per liter of air. C(t1,t2) denotes the counts observed from time t. to time t2 (in minutes) after the end of the 5-min sampling period. E is the detector efficiency and V is the flow rate in liters per minute. With an accuracy loss of less than -5% one finds from [Eq. 1] by adding the corresponding terms: If the WL would have been calculated according to [Eq. 2] instead of using the graph, the result would have been 0.31. Since the values used for C's under [Eq. 3] represent the exact number of counts from a Rn-daughter mixture in equilibrium with 100/3 pCi of Rn the exact WL of this mixture can be calculated easily. The exact value is: [ ] This shows that the method is quite accurate for the 0.3 WL domain. The precision of the method excluding errors made in reading the graph can be estimated with the help of the following formula: [ ]

Jan 1, 1974

By C. H. Mathewson

CHARACTER OF THE WORK IN HAND IN planning the present experiments, we have made a particular effort to secure that adjustment of working conditions which would render the forthcoming tests most serviceable by way of indicating the comparative properties of the three different commercial grades of copper used. More specifically, we have endeavored to obtain certain definite information with respect to the relative behavior under test of ordinary electrolytic copper and furnace-refined lake copper containing (a) a moderate percentage of arsenic and (b) a rather large percentage of arsenic, in addition to the usual content of silver and other impurities. These comparisons were made systematic and comprehensive by testing throughout a series of (eight) reductions running from 0 to 70 per cent. in the case of cold-rolled metal, and throughout a series of (15) temperatures running from 100° C. to 1,000° C. in the case of annealed metal. In other words, a survey of properties similar to that made by Grard,1 in the case of electrolytic copper, was here repeated (with modifications) and extended to two other commercial varieties of copper.

Jan 7, 1916

By A. M. Abouzeid, S. Chander, D. W. Fuerstenau

Today numerous ores contain valuable minerals in finely disseminated form; and although the recovery of these fine mineral particles is generally exceedingly difficult, diminishing raw material resources necessitates the recovery of such mineral values. In many systems, the efficiency of recovering fine particles is still extremely low and often fine particles must be discarded as slimes. However, in recent years, various advances have taken place in the recovery of mineral particles in the very fine size range. In this paper, the background and performance of a number of processes for fine particle processing and separation are reviewed and discussed, particularly from the point of view of how fine particle recovery might be improved.

Jan 1, 1979

By P. A. Beck, A. Merlini

Quantitative texture determinations were made for rolled and for rolled and annealed strips of 3, 6, and 10 pct Zn brasses. The main components of the rolling texture gradually shift over a wide composition range from the orientation characteristic of copper to that of 70-30 brass. At least the main features of the corresponding gradual changes in the annealing texture may be accounted for qualitatively on the basis of the oriented growth theory of annealing textures. All the oriented nucleation-type theories are notably less successful in accounting for the observed textures. EARLIER investigations by von Goeler and Sachs,' Dahl and Pawlek,' and Brick, Martin, and Angier" suggested that the annealing texture of copper is more sensitive to the addition of solute elements than the rolling texture. It was reported3 that the cube texture changes over into a brass-type recrys-tallization texture on addition of about 1 pct Zn, while the deformation texture changes only at about 5 pct Zn. Such behavior would be difficult to reconcile with any theory of annealing texture formation that relates the annealing texture to the deformation texture. In particular, the oriented growth theory of the cube texture" is based on a certain orientation relationship between the cube texture and the main components of the deformation texture which could not be reconciled with the reported behavior of low brasses. It was, therefore, of interest to re-examine these textures by means of the quantitative methods now available. The deformation and annealing textures of rolled a brasses with approximately 3, 6, and 10 pct Zn have been determined in terms of (111) and (200) pole figures. Experimental Methods The chemical analyses of the Cu-Zn alloys of commercial purity used in the present work are given in Table I. Chill-cast bars of the tabulated compositions were rolled and annealed according to the following schedule: I—rolling from 1.2 to 1.02 in. thickness, 15 pct reduction area, annealing 15 min at 450°C; 2— rolling from 1.02 to 0.867 in. thickness, 15 pct reduction area, annealing 15 min at 450°C; 3—rolling from 0.867 to 0.600 in. thickness, 31 pct reduction area, annealing 2 hr at 540°C; 4—rolling from 0.600 to 0.400 in. thickness, 33 pct reduction area, annealing 2 hr at 480°C. In the final straight rolling of 96.25 pct reduction area, the strips were reversed end to end after each pass. The final annealing temperature was determined for each alloy by annealing specimens of the cold-rolled strips in salt bath for 5 min at varying temperatures. The results of the hardness measurements are given in Fig. 1, where the final annealing temperature used for each alloy in determining the annealing texture is indicated by a cross.

Jan 1, 1956

By M. E. Nicholson

The solubility of carbon in Ni-Cu alloys was determined at 1000°C. The factors which limit solid solubility are discussed with particular reference to the influence of electronic factors. The results indicate the extent of solid solubility is a function of the density of states at the Fermi surface. THE solid solubility of an interstitial element is primarily limited according to Seybolt and Fullman1 and Speiser and Spretnak2 by (a) the strain energy produced when the solute atom takes its interstitial position, and (b) the partial molal free energies of the solid solution and the coexisting phases. In several binary systems of a transition and a noble metal, where there are no abrupt changes in strain energy or free energies of coexisting phases, the solid solubility of an interstitial third element drops abruptly to a negligible value at a composition corresponding to a complete filling of the "d-band." Such a decrease occurs in the case of hydrogen in the Pd-Ag system at 60 pct Ag.3,4 The solubility of carbon in Ni-Cu alloys seems to vary in a similar manner as indicated by the embrittling effect of carbon on these alloys. These al- loys are embrittled by slow cooling due to the precipitation of graphite. This embrittlement can be removed by heat treatment if the carbon content is less than the solid solubility limit at the heat-treating temperature. If the carbon content of the alloy exceeds the solid solubility at the heat-treating given temperxture, the embrittlement cannot be eliminated by solution heat treatment.' Since pure nickel has a carbon solubility of 0.25 wt pct6 at 1000°C, embrittlement is easily removed from commercial nickel and nickel-rich alloys, which may contain of the order of 0.10 wt pct C. Embrittlement due to carbon cannot be removed from Ni-Cu alloys containing 70 to 80 wt pct Cu by annealing unless: the carbon content is of the order of 0.04 wt pct CL or less."' Thus, it appears that the

Jan 1, 1962

By N. A. D. Parlee, E. M. Sacris

OVER 55 years ago, Sieverts and Hagenacker1 and Donnan and shaw2 made determinations of the solubility of oxygen in liquid silver, over a rather short range of temperatures (973° to 1125°C), using quartz bulbs, mainly at 1 atm. From the results of their investigations, Mizikar, Grace, and parlee3 plotted % O vs 1/T and obtained the following straight-line equation for solubility at 1 atm: log % O = 723.7/T - 1.0949 Recent work on the kinetics of the Ag-O2 system394 indicated there might have been some error due to reaction with the direct heated silica bulbs. Thus it became important to redetermine the solubility with the silver contained in a better refractory such as alumina, and by induction heating where the walls of the container were not so strongly heated. It was also desirable to extend the temperature range. A modified Sieverts apparatus of fairly standard type was used except that a special type of reaction tube was employed, Fig. 1. Dried argon with a guaranteed purity of 99.9 pet, and dried medical-grade oxygen with a guaranteed purity of 99.6 pet containing a little nitrogen, were the gases used. The measuring system consisted essentially of a manometer and a water-jacketed 100-cc gas buret with an open-end vertical tube parallel to the buret. This tube has the same diameter as the buret in order to give the same capillary effect on the mercury. A screw leveling device was used with the buret leveling bulb to help provide accurate pressure readings. A 2-mm ID capillary line connected the buret to the reaction chamber, helping to reduce the dead volume, which was determined with argon. The heating medium was a 2.5-kw output induction furnace. The induction coil was made of a 3/16-in. copper tubing with eight turns and an inside diameter of 4 cm. The reaction bulb was made of a quartz tube 18 cm long and 3 cm in inside diameter, Fig. 1. Inside the quartz tube were two alumina crucibles (Mor-ganite Triangle RR, XN10 and XN5) one inside the other. Below these two was an alumina disk. The disk prevented the corners of the outer crucible from expanding against the quartz tube. The solid sample (99.994 + pet Ag), which had been previously cleaned by air oxidation and repeated removal of scum, was placed inside the inner crucible. An alumina disk with a hole at the center covered the two crucibles. In order to decrease the dead volume, an evacuated quartz "filler" tube was placed on top of the crucible cover. The part of the reaction tube above the spherical joint was made up of Pyrex glass with a flat glass top. It was here that a prism was placed to facilitate the use of an optical pyrometer, previously calibrated at the freezing point of silver. This type of reaction bulb and furnace assembly was specially designed for this work, and used in preference to the relatively new water-

Jan 1, 1965

By S. Andrew Kulin, L. Kaufman

A general treatment of the broadening of X-ray double-crystal spectrometer rocking curves due to distributions of tilts and strains has been carried out. The results of this treatment have been applied to the case where dislocations in a crystal give rise to both tilts and strains. On this basis it is found that the rocking-curve halfwidth due to imperfections in the crystal, ßC , increases with increasing Bragg angle, 8. These considerations predict linear relationships between & and tan2 , and ßCand tan 8, for Gaussian and Cauchy distributions of dislocations, respectively. The zero intercept of the ßC us 8 curve, which is a measure of the degree of imperfection of the crystal, is found to depend directly on the distribution rather than the number of dislocations. In addition, the slope-intercept ratio for the ßc - ? curve has been calculated for both the Gaussian and Cauchy distributions. Experimental determination of the - 8 curves for a series of copper single crystals prepared by the Bridgeman and Czochralski methods yields results in agreement with the calculated slope-intercept ratio for a Cauchy distribution of dislocations. CERTAIN X-ray techniques have been used to study the perfection of single crystals. Gay, Hirsch, and Kelly have considered the spreading of spots into arcs on Debye-Sherrer rings due to imperfections. The Double-Crystal Spectrometer has also been applied to this problem.2 The characteristics of Double-Crystal Spectrometer Rocking Curves have been described in the literature by various workers.2-4 By assuming a random spacing of dislocations which give rise to a Gaussian distribution of misorientations relative to some mean orientation in a crystal Gay, et al.,1 arrive at the conclu- sion that the most probable misorientation is given by where h is the spacing between dislocations, and 8 and are the relative misorientations of neighboring regions. If ßC is the halfwidth of the rocking curve (the width at one-half the peak intensity) due to dislocations in the crystal then5

Jan 1, 1960

By F. F. Aplan, P. H. de Bruyn

The adsorption density of hexyl mercaptan was measured at the gold-solution and the gold-vapor interfaces. This collector is strongly adsorbed at low concentrations, a monomolecular layer being formed at the gold-solution interface at concentrations as low as 2 x 10'6 moles per liter. A maximum contact angle of 83 ± 3° is observed. From a thermodynamic analysis of the experimental data the changes in surface tension at the gold-gas and gold-solution interface are calculated. The data also suggest that the adsorption density of mercaptan at the gold-gas interface exceeds that at the gold-solution interface. In the equilibrium state, a simple flotation system consists of three phases, the solid to be floated, air, and an aqueous solution in stable contact along a line. During the process leading to this final state, a solid-gas interface is created at the expense of a portion of the liquid-gas and solid-liquid interfaces. This change of state is achieved by addition of a collector and, if necessary, suitable modifying agents to the system. By a combined application of the Gibbs Adsorption and the Young Equations, de Bruyn, Overbeek and Schuhmannl were able to show theoretically that the equilibrium distribution of the collector at all three interfaces determines the magnitude of the contact angle. Their analysis led them to conclude that the equilibrium adsorption density of the collector at the solid-gas interface exceeds its density at the solid- liquid interface. This paper succeeded in focussing attention on the neglected role of the solid-gas interface in flotation. In recent years the application of radiotracer, infrared, electrochemical and electro-kinetic techniques to studies of the solid-liquid interface2-5 enhanced our understanding of adsorption processes at this interface. Except for the measurement of contact angles, the solid-gas interface received no attention in fundamental flotation studies. In an attempt to apply the analysis of de Bruyn, Overbeek and Schuhmann to a simple flotation system, an investigation of the adsorption of hexyl mercaptan onto gold was undertaken. Gold was chosen as the solid phase in order to keep the number of dissolved chemical species in the solution phase to a minimum. Hexyl mercaptan (1 - hexanethiol) was selected as collector because its relatively high vapor pressure at room temperature makes it possible to obtain adsorption measurements at the solid-gas interface. This flotation system consists, therefore, of a pure solid phase (gold), an aqueous solution of a weakly dissociated collector (1 -hexanethiol), and a gaseous phase, nitrogen saturated with respect to both water vapor and mercaptan vapor. EXPERIMENTAL MATERIALS AND METHODS Materials: Liquid 1-hexanethiol (C6H13SH) was obtained from Distillation Products Industries and was further purified by double distillation. The purity of the final product was established by boiling point and refractive index measurements. For the adsorption studies from aqueous solution, the radiotracer element, sulfur-35, (half life 87.1 days, 0.169 Mev beta ray) was synthesized into the mercaptan by Tracerlab Inc., Boston, Mass. A close boiling fraction of the synthesized compound was used in the adsorption studies. The specific activity of the radioactive compound was 10 millicuries per gram.

Jan 1, 1963