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By Otto W. Nuttli

THE magnetic method of prospecting is well suited to determination of faulting in the basement rock. In addition to establishing the horizontal position of the fault, it often furnishes valuable information concerning the depth and amount of faulting. Consider a simple case of a vertical fault, represented in cross-section in Fig. 1. Let A A' represent the plane of observation (ordinarily the surface of the earth), and BB'B"B"' the upper surface of the basement. Assume that the sedimentary rocks are nonmagnetic, so that the magnetic susceptibility of the material above the basement is zero. Let k indicate the susceptibility of the basement rock, c the density contrast between it and the neighboring sedimentary rocks, and the amount of vertical displacement. Fig. 1 shows the material, indicated by cross- hatching, which gives rise to the magnetic anomaly. In most cases it can be assumed that is small compared to the thickness of the sedimentary rocks. The semi-infinite, rectangular slab of rock of susceptibility k, density contrast , and thickness t may then be replaced by a semi-infinite sheet CC' of mass t per unit area at depth 2 (the mean depth of the slab). Nettleton 1 states that this approximation results in an error of less than 2 pct for the computed gravitational field intensity when t is as great as 2/2 and decreases rapidly for smaller values of t. By a theorem of Poisson, the magnetic field intensity can be determined readily from the gravitational field. The theorem states that W = (I/) • (U/i) i1 [1] where W is the magnetic potential associated with the structure, I is the intensity of magnetization which is assumed to have the direction of the inducing field, ? is the constant of gravitation, the density contrast, U the gravitational potential associated with the structure, i the direction of the inducing magnetic field, and i1 a unit vector in that direction. The multiplication indicated in Eq. 1 is

Jan 1, 1956

By Richard H. Olson, Lawrence A. Roe

Talc, when it can be isolated as a pure mineral, has a composition of 63.36% Si02, 31.89% MgO, and 4.75% H20. However, as an industrial commodity, talc rarely approaches theoretical purity. Nevertheless, the impure talc products of commerce find a multitude of uses and few substitutes in many industrial applications. Minerals commonly associated with and sold together in talcose mixtures are tremolite, chlorite, dolomite, mica, and magnesite. Steatite was originally a mineralogical name applied to pure talc. In today's commerce steatite generally refers to the massive variety of talc suitable for electrical insulator manufacture. Block steatite ore can be machined into various shapes. Impure varieties of massive or block talc are still commonly referred to as soapstone. Soft massive talc, suitable for crayon manufacture, has been referred to as French chalk. It has been common practice to discuss talc, soapstone, and pyrophyllite under the same general heading. In the case of soapstone and talc, this is a natural thing since many different types of platy, soft minerals exhibiting a high degree of lubricity (commonly referred to as "slip") have been grouped together and called soapstone or talc. Further, there is a mineralogical relationship of pyrophyllite to montmorillonite and talc to hectorite. Thus, talc and pyrophyllite are sometimes referred to as clay minerals. When finely divided talc or pyrophyllite are combined with water in proportions to make a slurry, the end product does have the appearance of a clay-water mixture. Soapstone for utensils and ornaments was mined by prehistoric Indians on Santa Catalina Island, CA. In the mid-1800s, soapstone from deposits along the western foothills of the Sierra Nevada mountains was used by white settlers for building and ornamental stone and in the linings and foundations of furnaces (Anon. 1956). Previous to 1916, the annual recorded production in California did not exceed 2000 tons. In the period 1912 to 1918, output rose sharply when the Talc City, Western, and Silver Lake mines were put into operation. From 1916 to 1935, the state's annual output of talc was in the range of 9,000 to 20,000 tons. In the mid-1930s, the use of talc in wall tile grew rapidly. In California, the production of talc grew to 63,000 stpy in 1943. The post-war building boom helped California production to grow to 120,000 tons in 1951. In 1968, production was 165,000 tons, 1969 was 145,000 tons, 1970 was 185,000 tons, and 1972 was 155,000 tons. Talc mining in New York state dates to about 1878 when a Colonel Palmer and associates opened the first commercial talc mine on the Nelson Freeman farm near Talcville, New York. In 1893, this operation was sold to the International Pulp Co. which changed its name to the International Talc Co. in 1944. The company was acquired by R.T. Vanderbilt Co., Inc. in 1974. A new talc operation, the Gouverneur Talc Co. owned by the R.T. Vanderbilt Co., began operations near Balmat, NY, in 1948. The initial capacity of the processing plant was 200 stpd (Gillingham, 1950). Subsequent expansions have increased capacity to over 600 stpd. The Vermont talc industry began just after the start of the 20th century. Talc was discovered in the area of the present Johnson, VT, talc mine in 1902. The American Minerals Co. initiated plant operations at Johnson in 1904. The Magnesia Talc Co. opened a plant at Waterbury, VT, in 1913 (Burmeister, 1963; Trauffer, 1964) and acquired American Minerals Co. in 1923. The Waterbury mine has a long history as a producer of talc crayons. The Eastern Magnesia Talc Co. was formed in 1924 by a merger of the Eastern Talc, Co.

Jan 1, 1983

By Webster Hodge

MALL generators and motors are required to Soperate, in some critical applications, at temperatures where cold-worked silver-bearing copper re-crystallizes. Copper containing up to 30 oz Ag per ton has been used for many years to build the highest grades of commutators and slip rings. With failure of commutators impending because silver-bearing copper cannot withstand the stresses imposed at these higher temperatures, Cr-Cu was tried as a substitute with varying degrees of success. Cr-Cu proved difficult to fabricate because a critical heat treatment was necessary to obtain sufficient ductility. Besides, its rupture strength was shown to be low at operating temperatures, its electrical conductivity lower than desired, and its cost high. Furthermore, it often contained hidden flaws. The Nippert Electric Products Co. set out to find a better material by undertaking a research project with the stated objective of providing a material suitable for commutators that would have 1) a softening temperature above 750°F (400°C), 2) a minimum electrical conductivity of 90 pct of that of pure copper, 3) a strength not less that that of cold-worked silver-bearing copper, and 4) a materials cost of not over 1.5 times the cost of copper containing 25 to 30 oz Ag per ton. No commercial alloy met these specifications. However, it was found that copper containing from 0.18 to 0.35 pct Zr could be produced quite easily in the laboratory, and promised to fulfill the major requirements noted above. Interest naturally centered in the lower part of this composition range, since such alloys gave somewhat better electrical conductivities, and were lower in

Jan 1, 1958

By M. C. Flemings, A. A. Tzavaras

Analytical and experimental procedures are descrihed for quantitative determination of volume-fraction microporosity in metals by mimorarlio-graphg. The analysis assumes spherical pores but allows for the observed fact that pores or portions of pores smaller than a given thickness do not project an image on the film. Volume-fraction microporosity was measuured in cast low-alloy steel and shown to vary from 0.6 x 10-4 to 10 x 10 depending on mode of solidification and on whether the material was air- or vacuum-cast. The aim of work described herein was to develop a method of quantitative measurement of the volume fraction of microporosity in cast metals. Microporosity, present in nearly all castings and ingots, is always interdendritic in nature and may be large enough to be seen on a polished surface with the naked eye. More generally, it is smaller in size, and its detection more difficult. Three techniques might be considered for measurement of microporosity: 1) lineal analysis of a polished metallographic surface, 2) density measurement, or 3) quantitative microradiography. As will be shown later, volume fractions of porosity in directionally solidified castings may be the order of 10-4 to 10-3; such small amounts of porosity are difficult to identify and measure on a polished surface. Density measurement is also not a suitable technique (for alloys) when the volume fraction of porosity is low. This is because the density of the base metal is often not known within the necessary accuracy, due to microsegregation or partial phase transformations. In general, it is not possible to completely eliminate microsegregation without also altering the porosity. Because of the limitations of the foregoing techniques, quantitative microradiography was employed to determine amount of porosity. In recent work, microradiography has been found to be useful for qualitative measurement of porosity, including determination of size and shape of individual pores;&apos;)&apos; however, quantitative determination of amount of porosity has not been attempted. I) CALCULATION OF VOLUME-FRACTION POROSITY The following analysis employs procedures similar to those of Cahn and Nutting3 and Hilliard.4 Major simplifications are that pores are assumed to be spherical and to be present in sufficiently small quantities that no overlapping occurs. A basic difference from the previous treatments is that the limited "sensitivity" of microradiography is considered. Assume first 1) cavities are spherical and of uniform diameter, 2) cavities are randomly distributed, 3) volume-fraction porosity and specimen thickness to pore radius ratio are sufficiently small that overlapping of the projected images of cavities is negligible, 4) sensitivity is limited (i.e., holes or portions of holes of less than a given thickness do not project an image on the film). The sensitivity, is defined as: where 5 = minimum thickness of void from which an image will be projected on the film and t = specimen thickness. Now, from Fig. 1, it is possible to distinguish between two different types of holes. These are 1) holes whose centers lie within the region t/2 > X > 6/2, where X is distance from one surface of the specimen (positive into the specimen), and 2) holes whose centers lie within the region (6 — r) < X < 6/2, Holes whose centers lie outside X = (6 -r) project no image on the film. These two types of pores are considered separately below. Type 1 Pores. When 6 is greater than 0, the image of a spherical cavity of radius r appears on the film as a circle of radius a which is smaller than r. From geometry, Fig. 1: a2=r2-52/4 [2] where a = radius of image of pore on film and r = radius of pore. Since the pores are randomly distributed and spherical V =4/3pr2Nv [3] where V = volume fraction of voids and Nv = number of pores per unit volume and the number of images of Type 1 pores per unit area of film, N&apos;A, is

Jan 1, 1965

By George Steintveit

Det Norske Zinkicompani A/S was established in 1924, on the initiative of the Compagnie Royale Asturienne des Mines. Experimental electrothermic zinc production was carried out on industrial scale for a two-year period, but the problems of electrothermic smelting were not solved. A license for the electrolytic zinc production process was then obtained from the Anaconda Copper Mining Co. A plant for electrolytic zinc production was built, near the small fjord town of Odda in Hardanger, West Norway, The production was based on zinc ore from Spain, and cheap local hydro-electric power. The plant came into operation in 1929. Annual capacity, 36,000 tons. In 1964 a long-term agreement was concluded with Boliden AB by which Det Norske Zinkkompani is secured the raw materials basis for an expansion of the annual capacity to 100,000 tons of zinc, Since World War II, the company has been pursuing extensive research and development programs. As a result, various sections have been rebuilt: nev unloading and storage facilities, a 250 ton per day Fluid Bed Roaster with contact plant, new continuous leaching system, integrating the Jarosite Residue Process, new solution purification section - upgrading the solution quality for a 600 Amp/m2 current density Tank Room operation -, installation of induction furnaces for cathode melting with casting machines and automatic stacking of slabs. Simultaneously, instrumentation, and methods of automatic control have been developed and introduced, providing conditions for optimal plant operations.

Jan 1, 1970

By Peter R. Morris, Alan J. Heckler

THREE angles are required to specify the orientation of a crystallite with respect to a physical reference frame. The distribution of crystallite orientations in a polycrystal is thus a function of three angular variables. The most widely used experimental techniques for studying orientation in polycrystals lead directly to the pole figure representation, i.e., the distribution of the poles of certain crystallographic planes in terms of two angular variables. In recent years1-5 methods have been developed which permit determination of the (three-angle) crystallite orientation distribution from several (two-angle) pole figure distributions. In this work Roe&apos;s method has been applied to the study of orientation in hcp materials. The method is illustrated for commercial purity titanium sheet (Ti-70) which was cold rolled (65 pct reduction), annealed at 1450°F for 3 min, and air cooled. The grain shape was observed to be equiaxed after this treatment. EFFECTS OF PHYSICAL, CRYSTALLOGRAPHIC SYMMETRY In Roe&apos;s method the crystallite orientation distribution, w(?,?,F), is expanded in a series of generalized spherical harmonics 11(?,?,F) = E E E W^Zirmtye-tote-in* [l] 1=o ,,,=-I ,,=-I where { = cos 8. The set of Euler angles employed here is illustrated in Fig. 1. The axis for each rotation is denoted by a double arrowhead. The positive sense of each rotation is that of a right-handed screw advancing in the direction of the double arrowhead. The X, Y, and Z directions correspond to the rolling direction, cross direction, and normal direction, respectively. In the initial orientation (10.O), (12.O), and (00 . 1) planes are perpendicular to the X, Y, and Z directions, respectively. The IC/ rotation about the Z axis is carried out first by rotating X into X&apos;, Y into Y&apos;, and leaving 2 unchanged, i.e., Z&apos; = Z. The 8 rotation about the Y&apos; axis is carried out second by rotating X&apos; into X", 2&apos; into Z", and leaving Y&apos; unchanged, i.e., Y" = Y&apos;. The I$ rotation about the Z" axis is carried out last by rotating X" into X"&apos;, Y into Y"&apos;, and leaving 2" unchanged, i.e., 2"&apos; = 2". Any specified orientation of the X&apos;", Y&apos;", and Z&apos;" crystal-fixed axis system relative to the X. Y, and Z physical axes (rolling direction, transverse direction, and sheet normal direction, respectively) can be obtained by appropriate IC/, 8, and (F rotations. The Zl,, of Eq. [l] are the Jacobi polynomials, augmented by the square root of the weight function. The Zl,, are symmetric in m,n, i.e., Zl,,= Zlnm. For orthotropic physical symmetry and hexagonal crystallographic symmetry, the coefficients, W!,,, of the series are all real, W!mn = Wzfi, = Wlm~ = Wlfi~, 1 and m are even and n is restricted to 6k, where k = ...,-2,-1, 0, 1, 2, .-.. The determination of the Wlmn from pole figure data has been previously described.&apos;~~ The Zl,, may be written in multiple angle form

Jan 1, 1970

By AIME AIME

LEWIS EMANUEL YOUNG was elected a Director of the A.I.M.E. at the last Annual Meeting as a representative of District &apos;4, including. Ohio, West Virginia, and western. Pennsylvania and New York. He also represents the Coal Division, in which industry lie has actively participated- for nearly twenty years. Dr. Young was horn in Topeka, Kan., Oct. 1, 1873, received mining degrees from Penn State and ,-Iowa. State, and a Ph.D., from Illinois. The first part of his professional life was spent in teaching first as instructor in mining at Iowa State, second .as professor of mining at the Colorado School&apos; of Mines, third as director of the School of Mines and Metallurgy at Rolla, Mo., and finally he taught business

Jan 1, 1937

By F. J. Smit, S. C. Sun

Flotation variables were investigated for the re-clamation of phosphate from a Florida washer slime. Under optimum conditions, 92% of the phosphate was recovered. Further cleaning of the rougher flotation concentrate resulted in a product containing about 30% P2O5 with a phosphate recovery of 65%. The enormous amount of slimes rejected in the Florida pebble phosphate fields, containing roughly one-third of the phosphate in the pebble matrix,1 has long been considered as a serious problem to the industry. The mere disposal of these slimes has posed an almost insurmountable task for several investigators.2-5 Some companies still resort to huge surface dams, some covering 1800 acres, for slime disposal.6 Information on the recovery of fine phosphate from these slimes is scanty. Dry separation8 and electrostatic beneficiation8 were suggested, but would necessitate radical changes in the present mining and concentration methods. Haseman10 proposed the selective flocculation of colloidal phosphate with starch, while Ralston11 suggested the removal of clay from the matrix by amine flotation. Leaching of the slimes for recovering the small amount of uranium was attempted by the Battelle Memorial Institute12,13 but proved to be economically unfeasible. The purpose of the present investigation was to determine the optimum fatty-acid flotation conditions for reclaiming the phosphate discarded with the Bartow washer slime. Prior to the flotation experimerits, however, the size distribution and the minera-logical composition of the employed slime had to be determined.

Jan 1, 1963

By John J. Collins

Page Purpose and scope..................... 521 Core sampling......................... 521 Sludge sampling....................... 527 Combining core and sludge assays ...... 533 Deviation and surveying of drill holes. . . . 537 Conclusions........................... 544 Acknowledgments...................... 545 Bibliography.......................... 545 Purpose and Scope The purpose of this paper is to review a few of the problems involved in the interpretation of diamond-drill core and sludge samples, with the hope that it will stimulate discussion and bring forth some of the information on the subject that has been accumulated by various organizations. The release of these data would benefit the mining industry as a whole. Particularly valuable would be the details of drilling programs that have been tested by actual mining operations, as most of the available published material is unsupported by production records. The scope of this paper is limited to a few of the commonest problems of interpreting diamond-drill core and sludge samples and the deviation of holes. It does not include the description of routine operations performed by the drillers, nor the estimation of ore reserves. The methods of calculating reserves have been described,25,26,31,32,50,65 but more informa- tion is needed on the results shown by actual mining operations. Core Sampling The accuracy of diamond-drill-hole Sampling depends in large measure on the percentage of core recovery. As a general rule, the longer the run, the poorer is the recovery. Although the longer runs allow cheaper drilling costs, the determining factor should be the percentage of recovery desired. The problem is one of balancing accuracy against costs. Holes of larger diameter may show improved recovery, except as Joralemon* points out that there are some conditions in which small holes give better core recovery than large holes. This is particularly true, he says; in rocks like shattered quartzite, where larger core tends to break in angular fragments and grind up, while the diameter of smaller core is less than the distance between joint planes and grinding is not so serious. In a large measure the length of the sample run should depend on the type of deposit. Favorable drilling may allow uniform sample runs of 5 ft., 10 ft., or perhaps 20 ft. In veins or beds of relatively narrow widths and changing characteristics, however, the ore zone may be overrun and ground in a core barrel full of waste rock. Generally it is desirable to break the sample at a change in the rock or ore. Such a change; often indicated by a color change in the sludge water, should be a a for the driller to make a "dry" block and to pull out that run regardless of the length. Such a procedure permits the segregation of waste from ore samples so

Jan 1, 1946

By Hsun Hu

Three single crystal strips of a 3 pct Si-Fe alloy with approximately (110) [001], (210) [001], and (100) [001] orientations were rolled at room temperature to 30, 50, and 70 pct reductions in thickness. Their deformation and annealing textures were studied. In most cases, the change in texture upon recrystallization and subsequent growth can be described as rotations around the <I10 > axes. A < WO > rotational relationship was also observed. The temperature dependence of recrystallization textures was discussed. WhILE considerable data have been published on the rolling and annealing textures in silicon-iron crystals, very little study has been made on the texture formation at various stages of rolling deformation, and during the process of recrystallization. Dunn&apos; in some of his early works had studied the orientation of recrystallized grains in crystals cut out from lightly rolled (10 to 20 pct reduction) large grained sheets. He found that in most cases a third-order twin relationship exists between the crystal and the recrystallized grains. This orientation relationship actually corresponds to rotations around the <110> axes. The more recent studies of Dunn &apos; and of Dunn and Koh &apos;5 on the rolling and annealing textures in various silicon-iron crystals were concerned mostly with a cold-rolling reduction of 70 pct and annealing at 980OC for recrystallization. Reductions of similar magnitude were also employed by Walter and Hibbard in rolling columnar crystal aggregates of a silicon-iron ingot. A systematic study of the effect of rolling reduction on the deforma- tion and annealing textures is still lacking. Regarding the effect of annealing temperature on the texture formation, Dunn3 has observed a change in therecrys-tallization texture by annealing a 70 pct rolled (1 10) [001] crystal first at a low temperature then atahigh temperature. But the details of texture formation during the annealing treatments were not thoroughly investigated. The present investigation was undertaken to study the texture developments at various stages of rolling deformation and of the recrystallization process, so that a better understanding on the texture formation in silicon-iron crystals may be obtained. EXPERIMENTAL PROCEDURE The three single crystals used in the present investigation were selected from the group of single crystal strips previously prepared7 from a high grade commercial Si-Fe alloy with 3 pct Si. The thickness of these single crystal strips was 0.040 in. The orientations of the three crystals as determined by the X-ray back-reflection Laue technique are shown in Table I. Each of the three crystals was rolled at room temperature along the strip direction to 30, 50, and 70

Jan 1, 1962

By Herbert Johnson

DURING the past 10 or 12 years very little information has been made generally available concerning the commercial possibilities of separating materials by means of static electricity; and yet during that same period important improvements have been made in various branches of the science of electricity, which, when taken together, and applied to electro-static separation, have resulted in important improvements in that art as well. For example, much improvement has been made in high-voltage electrical equipment such as full-wave vacuum-tube rectification and improved mechanical rectification. Great strides have likewise been made in the development of insulators for high-voltage work, not only in the materials used but also in the design of the insulators themselves. Again, in another field, the development of air-conditioning equipment has improved the technique of controlling the surface condition, through drying or humidifying, of the various materials that are passed through the electrostatic separator. In many authoritative publications and textbooks, the electrostatic separation process is declared to require a balance far too sensitive for general commercial application. For example, one publication1 in the past has referred to an unfavorable effect on the process caused by varying atmospheric conditions such as humidity. Some2 have even gone so far as to state that sunlight and shadows may seriously affect the separating efficiency of the process. Such statements may have been true in the early development of the art, when the source of static elec-tricity was derived from a friction disk machine, such as the Wimshurst. The Blake Mosher equipment and the work of Huff in applying motor-generator sets, transformers and mechanical rectification overcame much of this kind of objection to the commercial application of the elec-trostatic separating process.

Jan 1, 1938

By M. E. Wadsworth, I. B. Cutler

Coprecipitation of anionic and cationic polyelectrolytes has been applied to floccula-tion of several mineral systems. Results obtained in a study of the flocculation of kaolinite and hematite suspensions of polycationic and polyanionic electrolytes are presented. Greatly increased settling rates were observed following precipitation of positive and negative polyelectrolytes on the surface of finely divided minerals in aqueous suspension. The ratios of polycationic to polyanionic electrolytes required to produce maximum sedimentation have been shown to correspond closely with the equivalence points obtained by light scattering studies of systems containing the positive and negative polyelectrolytes by themselves. DISPERSION of colloids has been of interest to surface chemists for many years. Flocculation studies have been employed to evaluate the limits of colloid stability. In water suspensions, colloids become unstable and flocculate when the ( potential, the potential of the kinetic solvation sheath, falls to a value at which van der Waals forces may act to draw the particles together. This may happen through an adjustment of the pH of the suspension or by addition of a salt. Optimum conditions for rapid formation of large flocs are found in the region of minimum ( potential. In addition to these well known considerations, colloids in water suspensions are known to be flocculated by certain large organic macromolecules. These polyelectrolytes in some cases minimize the i potential and in other instances increase the attractive forces by supplying sites for hydrogen bonding.&apos; Use of organic polyelectrolytes in flocculation of mineral colloids has increased rapidly in recent years. These materials are now recognized as indispensable aids to fluid-solid separations in many extractive metallurgical operations. They have been found to increase both the settling rate in thickeners and the filtration rate of filters. In the elucidation of the characteristics of these organic reagents as floc-culants in this laboratory, it was discovered that interaction of certain polyelectrolytes had a surprisingly good effect on flocculation of mineral colloids. Experimental Procedure: The anionic flocculants used in this study were Lytron 886 and 887, produced by Monsanto Chemical Co. Both reagents are copolymers of vinyl acetate and maleic anhydride. Lime is added to Lytron 886, whereas Lytron 887 is all organic. These reagents possess two carboxyl groups for each acetate group and are therefore anionic in character. The cationic reagents used were the Peter Cooper Co. 1-X and 2-X glues. The structures are not definitely known, but the re- agents are amines and are cationic in character. The glues were prepared in the chrome-alum form. Both types of reagents may be classified as polyelectrolytes in that they are high molecular weight polymers and ionize in water. All data presented are in terms of sedimentation rate, measured in 250-ml glass-stoppered graduated cylinders. With suitable precautions such measurements are fairly reproducible and provide a sensitive means for selecting important parameters such as pH, reagent concentration, and floc size and density.2 Agitation was standardized with five complete end over end cycles of the suspensions in the stoppered graduated cylinders.

Jan 1, 1957

By E. I. Larsen, E. F. Swazy, F. R. Hensel

EXPERIENCE has indicated that hard bronzes are not suitable for bearing applications where high bearing loads and speeds are involved. It is the general practice to utilize softer materials for these purposes, such as copper, lead, silver, babbitt, lead-base alloys, and more recently aluminum-base alloys, preferably supported by a steel backing. It was the objective of the present investigation to study a new material produced by powder metallurgical methods susceptible to precipitation-hardening. TEST MATERIALS Preliminary tests were made with compacts containing copper, nickel and silicon in quantities sufficient to form 3 to 5 per cent nickel silicide. It was found that this type of alloy was susceptible to the formation of a soft surface shell when sintered in tank hydrogen. The depth of the shell depended on the length of sintering time and sintering temperature, and varied in thickness from a few thousandths to as much as one eighth inch. This soft shell resulted from the preferential oxidation of silicon, thereby reducing the efficiency of age-hardening by the nickel silicide compound. The body of the sintered compacts below the soft shell could be precipitation-hardened to a hardness of 70 to 85 Rockwell B, by quenching from. 900°C. and age-hardening at 450°C. A series of tests was made with various addition agents, in order to decrease the rate of preferential oxidation, and it was found that phosphorus was most beneficial in this respect. After considerable experimentation, the following nominal composition was accepted as standard: 2.4 per cent nickel; 0.8 silicon; 0.3 phosphorus; balance copper. The physical properties and certain bearing properties of this alloy are described in the present paper. PREPARATION OF COMPACTS Several methods of incorporating the hardening ingredient (nickel silicide) were studied. Compacts formed from copper, nickel and silicon powders were found to be inferior to those fabricated from prealloyed nickel silicide master alloys, because of the rapid oxidation of pure silicon during sintering. The use of a prealloyed nickel silicide hardener containing 25 per cent silicon and 75 per cent nickel could be further improved by preparing a master alloy, incorporating nickel, silicon, phosphorus and copper, having the following nominal composition: 25 per cent nickel; 7 silicon; 3 phosphorus; 64 copper. This alloy is brittle in. the cast condition and can be readily powdered. SINTERING PROCEDURE The blended powders were pressed at 25 to 40 tons per sq. in., the pressure depending on the size and shape of the compacts. Sintering was carried out in hydrogen or cracked ammonia atmospheres at

Jan 1, 1946

By R. A. Deju, R. B. Bhappu

The basic structural unit of all silicate minerals is a tetrahedron with a silicon atom at the center and four oxygen atoms at the corners. The oxygen-silicon distance is about 1.6 & and the oxygen-oxygen distance about 2.6 &. The different types of oxygen-silicon frameworks in the various silicates are based entirely on the combinations of the tetra-hedral oxygen-silicon groups through sharing of oxygen atoms. In recent years, infrared spectroscopy has permitted estimation of the ratio of the ionic character of the oxygen-silicon bond to be a few times that of the oxygen-carbon bond and the ratio of electro-negativity of the two bonds has also substantiated this finding. On this basis, it is generally accepted that the oxygen-silicon bond is the strongest one occurring in silicate minerals. As the oxygen-silicon ratio increases from quartz to the olivines, a greater percentage of the oxygen bonding power is available for bonding to cations other than silicon. Hence, with an increasing oxygen-silicon ratio, there is increasing oxygen-to-metal bonding. Upon the fracturing of a silicate mineral crystal, the oxygen-metal bond, which is almost entirely ionic in character, should break more easily than the stronger oxygen-silicon bond, resulting in a greater number of unsatisfied negative forces on the surface. If, then the mineral is immersed in a liquid containing hydrogen ions, these negative forces should tend to be neutralized by hydrogen ions from solution, resulting in a change of the pH of the solution. An increase in the degree of adsorption of hydrogen ions is to be expected as the oxygen-silicon ratio in the crystal structure increases. This study attempted to correlate the oxygen-silicon ratio for various representative silicate minerals to the adsorption of hydrogen ions. Experiments to determine the effect of surface area on this adsorption and to investigate the effect of surface iron were also conducted. It is believed that such studies of the surface properties of silicate minerals will supply pertinent information about their behavior in froth flotation systems. EXPERIMENTAL PROCEDURE Ion Exchange: Carefully selected, hand-picked samples of the minerals investigated were dry-crushed in a ceramic ball mill and sieved to obtain a minus 100 plus 200-mesh sample. The sized samples were then run through the electro-magnetic separator to remove any iron-bearing particles. A 10-g sample of each mineral was placed in 100 ml of freshly deionized water previously adjusted to a pH of 3.50 with HCl. The beaker containing the sample and the water was placed under a bell jar from which the air was displaced at once by nitrogen gas from a tank. All experiments were carried out in a nitrogen atmosphere. The sample and solution were stirred gently but continuously during the entire experiment, the stirring speed being kept about the same for all runs. Changes in pH were followed with a Beckman Zeromatic pH meter and recorded on a

Jan 1, 1967

By T. D. Murphy

This chapter deals with those types of silica raw materials that have been segregated and refined by natural processes into nearly monomineralic deposits and hence, by virtue of their high degree of purity, have become the sources of commodities having special and somewhat restricted commercial uses. In some instances, these raw materials occur in nature as unconsolidated quartzose sand or gravel and can be exploited and used with very little preparation and expense. More often, they occur as sandstone, conglomerate, quartzite, quartz mica schist, or massive igneous quartz which must be crushed, washed, screened, and sometimes chemically treated before commodities of suitable compositional and textural characteristics can be successfully prepared. The occurrence and distribution of silica raw materials is summarized and an effort has been made to bring commodity definitions, critical properties, and specifications up to date. Presentation of mining and processing methods is considered beyond the scope of this article; they are, for the most part, conventional and well known. New production techniques are currently reported in the trade journals and are later adequately described in technical publications as promptly as competitive restrictions allow. Discussion on Basis of Use ABRASIVE USES Industrial silica used for abrasive purposes falls into three main categories: (a) blasting sand; (b) glass-grinding sand; and (c) stone-sawing and rubbing sand. Blasting sand is a sound closely-sized quartz sand which, when propelled at high velocity by air, water, or controlled centrifugal force, is effective for such uses as cleaning metal castings, removing paint and rust, or renovating stone veneer. It is commonly referred to as Sand Blast sand. Multicycle quartz sand is an efficient blasting agent by merit of its survival characteristics which are soundness, toughness, and hardness. Steel grit and shot have supplanted it to a large extent but owing to their higher cost and tendency toward deterioration in storage, are still not universally used. It is conceded that angularity promotes faster cutting but this is offset by a higher loss in fines. The peening action of a rounded grain is a desirable feature in achieving a satin finish for certain light metal castings but a subangular grain is unsurpassed for fast heavy cutting. Specifications are chiefly based on size frequency distribution but it is mandatory that the grain be free of adhering clay or irony coatings. Material that dusts upon handling will not be tolerated. There is no uniform trade designation for the many blasting sand grades. Most producers sell on the basis of numbered grades; that is, No. 1, No. 2 and so on, this generally connoting fine to coarser grades. Designation of grade by the two sieve sizes between which most of the material lies, is practiced in some areas. Thus, in a No. 1220 grade, 98 pct of the material passes a 12 mesh sieve and is retained on a 20 mesh sieve. Blasting sand specifications vary according to use. Coarse grades range from 4 mesh to 12 mesh, medium grades range from 12 mesh to 30 mesh, finer grades may range from 20 mesh to 100 mesh or finer. Specifications generally call for narrow limits of gradation, requiring precise sizing methods. The fact that most blasting sands are retained

Jan 1, 1960

By J. M. W. Mackenzie, C. J. Wood

In attempting to describe the size classification performance of a hydrocyclone, most workers have elected to use either an equilibrium orbit theory or an non-equilibrium orbit theory. The equilibrium orbit theory has been used by the majority of workers including Lilge,&apos; Bradley; and Yoshioka and Hotta. In applying this theory, it is argued that particles in the body of a hydrocyclone attain an equilibrium radial position where the drag force on the particle resulting from the inward radial fluid velocity is balanced by the outward centrifugal force caused by the tangential component of fluid flow. When considered over the full height of the hydrocy-clone, attainment of this radial equilibrium orbit results in the particle following a conical equilibrium envelope. It is then argued that if this envelope lies outside the envelope of "zero vertical velocity," the particle will report to the underflow, while if the equilibrium envelope lies inside the envelope of "zero vertical velocity," the particle will report to the overflow or vortex finder product. The d50-sized particle which reports in equal quantities to the underflow and overflow is assumed to correspond to particles whose equilibrium envelope is coincident with the envelope of "zero vertical velocity." In considering the equilibrium orbit theory, it is apparent that the horizontal position of the particles in the feed inlet pipe should have no effect on their ultimate destination on the hydrocyclone. Each particle should attain an equilibrium position which depends on the density, size, and shape of the particle; the density and viscosity of the fluid; and the flow patterns within the hydrocy-clone. The nonequilibrium orbit or unsteady state theory has been largely developed by Rietema4 and Mizrahi.6 Mizrahi has listed four main objections to the equilibrium orbit theory. These objections center on the short residence time in the hydrocyclone, the fact that the experimental classification curve is much less sharp than is theoretically predicted, and the absence of negative efficiency conditions in hydro cyclones operating on a feed material which is much finer in size than d50. Proponents of the nonequilibrium orbit theory argue that for a particle to discharge with the underflow it must have sufficient outward radial velocity to reach the downward-flowing region close to the hydrocyclone wall in which the flow lines are parallel to the wall and the ratio of vertical to radial velocity is constant. It is then postulated that a d50 particle entering the cyclone at the center of the feed inlet will just reach this downward-flowing region as it reaches the apex. Thus for uniform distribution of particles across the feed inlet, half the d50 particles—that is, those injected in the half of the inlet area nearest the cyclone wall —will report to the underflow while those injected in the other half will not reach the downward-flowing region and will be carried inward to the center of the cyclone and thus report in the overflow. The exact thickness of the down-ward-flowing region of fluid adjacent to the outer wall of the hydrocyclone is uncertain but Mizrahi considers it to be equal to the apex radius minus the air core radius. Particles larger than d50 have a greater outward centrifugal force acting on them than the d50 particles and may reach the wall even if injected at a distance from the wall greater than Di/2 (Di is inlet diameter). Conversely, particles smaller than d50 may not reach the wall even if injected at a distance less than Di/2 from the cyclone wall. Since the equations put forward by the proponents of both theories yield approximately the same values of d50, it is not possible to decide between these theories by measurement of d50. It should be possible however to examine the theories by injecting a small stream of solids into the feed inlet of a hydrocyclone running on clear water. If the efficiency or classification curve is measured for various horizontal injection positions, then the curves should be coincident if the equilibrium orbit theory holds. If, however, the unsteady state theory describes the cyclone operation, then the classification curves should show finer d50 sizes for particles injected close to the cyclone wall. Experimental A 6-in.-diam hydrocyclone with geometry as in Figs. 1 and 2 was used. Quartz particles were injected as a 50% by wt pulp via an 1/8-in. steel probe. For each in-

Jan 1, 1971

"The 100,000 volt sub-station at Butte is located near the center of the district in which the power is distributed. The sub-station building is 150 feet by 50 feet in plan and 50 feet high. It is a brick walled, steel framed structure with concrete floors and roof.There are installed at present four banks of single-phase transformers, rated at 3,600 k-w. per bank and connected in delta on both high and low tension sides. They step the voltage down from 102,000 to 2,500, at which voltage it is distributed to customers. The transformers are installed in fireproof compartments, entirely shut off from the rest of the building by brick walls and opening only out of doors. The transformers are mounted on wheels and can readily be run out onto a flat car, which stands on a track running parallel with the building in front of the row of transformer compartments. This arrangement furnishes a convenient method of handling the transformers, both at the time of installation and afterward, in case it is necessary to make repairs."

Jan 1, 1913

By H. R. Peiffer

Recently artin has indicated that the recovery of resistivity at 145°C following elongation of molybdenum at room temperature was the result of the annihilation of vacancies. The activation energy for this process was, according to Martin, 1.26 ev. This energy seems to be a reasonable one for the activation energy for the diffusion of vacancies in molybdenum. However, impurity atoms such as carbon, nitrogen, and oxygen4 have an activation energy for diffusion in molybdenum of the same order of magnitude (i.e., 1.45, 1.15, and 2.09 ev, respectively). Cottrell and Churchman have already correlated the return of impurity atoms to dislocations in cold-worked iron with the return of the upper and lower yield point. According to cottrel16 the diffusion of carbon atoms to dislocations results in the return of the yield point. As the carbon atoms become trapped by dislocations, Bhatia has shown that a decrease in the electrical resistivity is to be expected. Cottrell and Churchman were able to correlate experimentally the decrease in electrical resistivity with the return of the yield point. Since one would expect strain aging to occur in molybdenum, an experiment was performed to determine whether the resistivity recovery at 150°C for molybdenum cold-worked at room temperature can be correlated with the return of an upper and lower yield point. For this experiment 3/16-in. tensile bars of Climax molybdenum, 99.961 pct pure, were used. The specimens were annealed at 1000° C for 1 hr in an argon atmosphere and then were elongated up to 10 pct on a Baldwin-Lima-Hamilton FGT

Jan 1, 1959

By Theodore Hatch

The pneumatic rock drill operates essentially as a crusher. The rock is shattered into a powder that is removed from the drill hole by the air stream introduced through the hollow drill steel. Particles thus produced vary in size from 1/4 in. or larger down to diameters too small to be revealed by the ordinary microscope. The power consumed by the drill is proportional to the new surface area of the powdered material, therefore the greater the proportion of "dost" produced, the higher the power consumption and the lower the drilling speed. A considerable amount of material ejected from the hole settles on the rock and much of this falls back as the mound builds up to be crushed further before it is removed again. The cushion of dust at the bottom of the hole reduces the effectiveness of the blow of the bit and thus lowers the rate of drilling. The unfavorable working conditions created by the dust also reduce the drilling speed by lowering the efficiency of the operator. Thus, the dust produced by rock drills constitutes a serious drawback to economical performance on all drilling operations. To the economic objections, one must add the more important objection to the health hazard created when the dust contains free silica (quartz). The silicosis problem is a familiar one in many mines, tunnels, and other underground operations as well as in quarries and other types of open rock excavation. Dust is a necessary end product of all pneumatic drilling operations. Its production cannot be eliminated although the proportion of microscopic particles can be reduced by using improved drill steel, proper methods of sharpening, more efficient drills, etc.—improvements that increase the drilling speed largely by increasing the size of the cuttings. The absolute improvement secured in this way is not great, however, and the pneumatic drill must always remain a dust-producing machine. Definite benefits do result, on the other hand, from the use of dust-control equipment that captures the dust as it emerges from the hole and conveys it to a remote point of discharge. Dust production continues, but dust dispersion into the atmosphere is prevented. The dust is removed as rapidly as it is formed, with the following results: (I) The silicosis

Jan 1, 1937

Z. W. Bartlett, J. C. Carrington, H. C. Petersen and K. T. Price were elected vice-presidents of the Freeport Sulphur Co. Blandford C. Burgess was transferred on January 1 to the new Defense Materials Procurement Agency as strategic materials specialist. In May the Region III headquarters of this organization was moved to London. L. C. Campbell was elected president of National Coal Assn. Mr. Campbell, who has been a member of the National&apos;s Board of Directors and Executive Committee for many years, is vice-president of the Coal Div. of the Eastern Gas & Fuel Associates and in charge of their extensive mining operations in West Virginia, Pennsylvania and Kentucky. Vern H. Christoph has been transferred to Panama Canal Co., Marine Bureau, Navigation Division, Port Captains Office, as an admeasurer at Cristobal, Canal Zone. Eugene Cline, recently graduated from the University of Kentucky, has been employed by Pond Creek Pocahontas Coal Co., at Evanston, Ky. Sanford S. Cole, assistant manager of research at the Titanium div. of National Lead Co., received the Alumni Citation from his alma mater, Alfred University, Alfred, N. Y. This was in recognition of outstanding achievements and services in the field of ceramics which have brought honor to the institution. U. K. Custred, recently graduated from University of Kentucky, and may be reached now at Box 87, Monterey, Tenn. Robert E. Dwyer, executive vice-president of Anaconda since 1940, was recently elected president of this company and its subsidiaries, Chile Copper Co., Chile Exploration Co., and Andes Copper Mining Co. As president, Mr. Dwyer succeeds the late William H. Hoover who died in Butte, Mont.

Jan 1, 1952