Search Documents

By A. F. Crawley

THIS paper describes part of a series of density measurements on low melting point metals being undertaken at the Mines Branch, Department of Energy, Mines and Resources, Ottawa, Canada. This program has received support from the Canadian Zinc and Lead Research Committee and the International Lead and Zinc Research Organization. Examples of the type of work being done have already been given in earlier papers' , which deal with the densities of lead, tin, and some of their alloys. Densities were measured using a graphite pyc-nometer by a technique which has already been described." The cadmium and indium, supplied by the Consolidated Mining and Smelting Co. of Canada were of 99.999 pct purity. Density determinations on indium, as for lead and tin,1,2 were made under a vacuum of about 5 x 10-6 torr because the oxidation and vaporization characteristics of the metal do not create experimental difficulties. This contrasts markedly with cadmium which, even at the relatively low temperatures of our experiments, has a high vapor pressure and a strong oxidation potential. To suppress the harmful effects of these properties, determinations on cadmium were made with success under an atmosphere of argon, the technique having been previously established in this laboratory for measurements on zinc.3 The densities of cadmium and indium are listed in Table I and plotted in Figs. 1 and 2. From the graphs, it is readily observed that the densities of both metals vary linearly with temperature. This relationship expressed mathematically is of the form:

Jan 1, 1969

By S. G. Bankoff

INCE1 proposed that electrostatic attraction between oppositely charged particles was responsible for slime-coating. Del Giudice2 postulated the metathetic formation of a cementing compound. Wark3 suggested that prevention of slime-coating was related to peptization of the slime. [ ] In the experiments of Table I the technique employed was essentially that of del Giudice, with the difference that the particle was examined under a film of water rather than dry.4 In general, the polished particle was agitated for 2 min. in a pulp consisting of 12.5 grams of the slime (-200 mesh) and 50 c.c. of distilled water, washed in three baths of distilled water, and examined at 220 diameters with the Leitz Ultropak. Observations of Brownian movement were made at 850 diameters with dark-field illumination. Several of these experiments do not jibe with the metathesis theory. According to published solubilities,5,6 the lead salts of the anions in experiments [c] through g are more insoluble than lead carbonate, therefore should prevent the formation of lead carbonate on the galena surface. In experiment [i] the calcium oxalate, which presumably was on the calcite surfaces, should have permitted the formation of a lead carbonate cement by virtue of its greater solubility. Experiments [j] through m show that the addition of lime accelerates the deposition of quartz onto a galena surface. The writer is unable to postulate a satisfactory cementing compound, according to the metathesis theory, to explain this effect. These experiments led to the conclusion that the metathetic formation of a cement-

Jan 1, 1941

By S.G. Bankoff

Ince1 proposed that electrostatic attraction between oppositely charged particles was responsible for slime-coating. Del Giudice2 postulated the metathetic formation of a cementing compound. Wark3 suggested that prevention of slime-coating was related to peptization of the slime. In the experiments of Table I the technique employed was essentially that of del Giudice, with the difference that the particle was examined under a film of water rather than dry.4 In general, the polished particle was agitated for 2 min. in a pulp consisting of 12.5 grams of the slime (—200 mesh) and 50 C.C. of distilled water, washed in three baths of distilled water, and examined at 220 diameters with the Leitz Ultropak. Observations of Brownian movement were made at 850 diameters with dark-field illumination. Several of these experiments do not jibe with the metathesis theory. According to published solubilities,5,6 the lead salts of the anions in experiments c through g are more insoluble than lead carbonate, there- fore should prevent the formation of lead carbonate on the galena surface. In experiment i the calcium oxalate, which precumably was on the calcite surfaces, should have permitted the formation of a lead carbonate cement by virtue of its greater solubility. Experiments j through m show that the addition of lime accelerates the deposition of quartz onto a galena surface. The writer is unable to postulate a satisfactory cementing compound, according to the metathesis theory, to explain this effect. These experiments led to the conclusion that the metathetic formation of a cement-

Jan 1, 1943

By S. G. Bankoff

Ince1 proposed that electrostatic attraction between oppositely charged particles was responsible for slime-coating. Del Giudice2 postulated the metathetic formation of a cementing compound. Wark3 suggested that prevention of slime-coating was related to peptization of the slime. In the experiments of Table I the technique employed was essentially that of del Giudice, with the difference that the particle was examined under a film of water rather than dry.4 In general, the polished particle was agitated for 2 min. in a pulp consisting of 12.5 grams of the slime (—200 mesh) and 50 C.C. of distilled water, washed in three baths of distilled water, and examined at 220 diameters with the Leitz Ultropak. Observations of Brownian movement were made at 850 diameters with dark-field illumination. Several of these experiments do not jibe with the metathesis theory. According to published solubilities,5,6 the lead salts of the anions in experiments c through g are more insoluble than lead carbonate, there- fore should prevent the formation of lead carbonate on the galena surface. In experiment i the calcium oxalate, which precumably was on the calcite surfaces, should have permitted the formation of a lead carbonate cement by virtue of its greater solubility. Experiments j through m show that the addition of lime accelerates the deposition of quartz onto a galena surface. The writer is unable to postulate a satisfactory cementing compound, according to the metathesis theory, to explain this effect. These experiments led to the conclusion that the metathetic formation of a cement-

Jan 1, 1943

By George Kunz

(Butte Meeting, August, 1913.) THE manifold inconveniences resulting from the absence of a uniform standard of mass for determining the weight of precious stones have long been obvious. This lack has been keenly felt in commercial transactions, and those who have devoted time and research to the study of historic diamonds and precious stones have had frequent occasion to deplore the absence of such a standard in the past. In a paper read in Chicago in 1893, before the International Congress of Weights and Measures, held in connection with the World's Columbian Exposition, the writer suggested dividing the carat into 100 parts, and constituting a standard international carat of 200 mg. ; that is, 5 diamond carats or 20 pearl grains to a French gram, making 5,000 carats or 20,000 pearl grains to a kilogram. He also called attention to the fact that while this would depreciate the present diamond carat or pearl grain only about 2.5 per cent., it would abolish the troublesome discrepancies between the various carat-weights now in use, and could be easily explained and understood everywhere.1 The subject of the various diamond carats, their incongruity, and the resulting confusion as to the correct weights of historic gems when definite records of them are searched for, has been fully treated by me in an extensive study of this subject in The Book of the Pearl.2 To the earnest and unremitting efforts of C. E. Guillaume, Director of the Bureau Internationale des Poids et Mesures at Sèvres, is largely clue the eventual success of this eminently desirable reform, which lie has constantly urged both by articles on the subject and by addresses delivered in Paris before the International Committee for Weights and Measures.3

Jan 7, 1913

By A. E. Bellis

The time effect in reheating certain steels below the critical range is very marked. The increased toughness, shock-resisting power, and machinability of steel subjected to a long, high drawing temperature has been thoroughly demonstrated and is of practical importance, particularly in the manufacture of L'smokeless" rifle-barrel steel. The time effect in tempering is most important when a maximum drawing effect is desired, in which case the highest physical properties as well as ease of machining are important considerations. These are the conditions in drilling a rifle barrel. A hole, 0.30 in. in diameter and 24 in. long for the Springfield rifle, and 30 in. long for the Russian military rifle, has to be drilled in the heat-treated material. This barrel-drilling operation is probably the most difficult one in rifle manufacture, and anyone who has been connected with rifle manufacture knows how seriously production is affected when "hard" or non-uniform steel for barrels is encountered. The importance of high physical properties (tensile strength, toughness and resilience) in a rifle barrel is obvious. The physical properties of two different lots of barrel steel are given below. The first lot, No. 1, gave serious trouble in the drilling operation; the second gave no trouble at all. No. 1 No. 2 Elastic limit, lb. per sq. in.................... 117,450 116,800 Tensile strength, Ib. per sq. in................. 132,500 131,750 Elongation, per cent........................ 16.0 20.0 Reduction of area, per cent................... 42.1 51.0 Impact strength, ft.-lb. per sq. in.............. 450.0 520.0 This difference in machining and physical properties was due entirely to the time of reheating. The first lot was given a reheating time of 30 min., the second lot remained at the reheating temperature 2 hr. Both

Jan 1, 1918

By J. B. Urnfileb

THE function of gas in the development and production of oil has far reaching consequences that should be emphasized. The technical aspects of the subject have recently had a great deal of attention but less thought has been given to fundamental concepts underlying oil and gas law and the many customs and practices that have grown up in the industry. I shall re- view briefly the advance in knowledge of the subject and attempt to relate these concepts to legislative, judicial and operating problems. Early writers on oil and gas in Pennsylvania noted their close association in oil pools and their contemporaneous decline in output; also, that as gas pressure decreases so does production, that new offset wells reduce the output of existing wells, and even that tubing a well lengthens its flowing life. Expanding gas was deduced as the principal expulsive force. These fundamental observations had been made at least as early as 1880.l They were treated, however, as academic considerations and did not greatly influence law or practice for many years except to instil into all operators an urgent desire to hasten offset drilling to obtain as much of the flush as possible.

Jan 1, 1932

By A. C. Stevenson

THE hoisting equipment selected for use at the Hecla mine in 1907 was one of the first Ilgner type Ward-Leonard controlled hoists put into ser- vice. Development of the Hecla below the 2000-ft. level, which is the ultimate depth of the old equipment, and the additional service required by the "Star," necessitated additional hoisting capacity. It will be our endeavor to give j70u a brief summary of the engineering which determined the selection of the new equipment. The engineer in making his decision as to size, speed, etc., must .make a duty study approximating as closely &s possible the actual opePating conditions which will eventually result. Primarily, it is necessary to know what work must be done. The amount of material which must be hoisted under the maximum condition, as well as its distribution from the various levels of the mine was carefully studied by the mining engineering department, as the ore reserves, their relative-position and the probable method of working them had to be considered. The final figures reached, taking into consideration four different operating conditions, were, in tons per day, as follows:

Jan 1, 1930

By Carville E. Sparks, Rollin Farmin

TRIAL installations of rock bolts, of the slit-rod-and-wedge type, were under way at several units of Day Mines, Inc., when Korean hostilities interrupted the already slow deliveries of steel bars to the Coeur d'Alene district. Factory-made bolts had not yet been put on the local market, so the program was halted for lack of supplies. Interest was revived by a visitor's description of wooden roof bolts. These were said to have been used briefly with apparent success in a coal mine, until apprehension voiced by the U. S. Bureau of Mines caused the practice to be suspended. To make wooden bolts for trial in ground support, Day Mines acquired a second-hand doweling machine equipped with two cutting heads, one to turn out the desired round rods of 2-in. diam, the other to turn out 1-in. rods to be used as powder-tamping sticks. This machine was installed in the all-weather sawmill of the Hercules mine unit at Burke, Idaho, where fabrication of the wooden bolts commenced early in 1951. Most of the mining in the Coeur d'Alene district is along steeply dipping veins in shaly quartzite and argillite of Algonkian age. Ground support commonly is required in zones where the rocks have been sheared, brecciated, and hydrothermally altered. Pressure from the sidewalls is more troublesome than weight overhead, but both increase with the size of the mine opening. Caving may come from a progressive sloughing of irregular rock fragments or from an exfoliation and buckling of the layered wall rocks. The disintegration is thought to develop from an initial elastic expansion of the rock toward the newly-created mine opening, followed by the dilation of many tiny partings in the rock by absorption of water. As the partings widen, masses of rock develop weight and become free to fall. The function of rock bolts is to prevent or retard widening of partings in the rock supported. Wooden Bolts, Wedges and Headboards Bolt assembly used by Day Mines consists of a bolt 4 or 6 ft long, two wedges 16 in. long, and a headboard 30 in. long, Fig. 1. All four pieces are made of local red (Douglas) fir, either green or well-soaked in the mill pond before it enters the sawmill. Bolts are fabricated from cants, 2 1/4 in. sq, cut from relatively straight-grained timber with a minimum of knots and trimmed to 4- and 6-ft lengths. The bolt then is turned in the doweling machine from 21/4 in. sq to 2 in. diam round, except for a 4-in. length at one end which is left full square to provide the striking head and the shoulder that holds the headboard in position for wedging. The foot end of the bolt is slit with a thin saw for a length of about 16 in., thereby making a slot to receive the wedge against which the bolt is driven for anchorage at the bottom of the rock hole. A similar slit, 12 in. long, is made in the opposite (head) end of the bolt to receive the second wedge, which crowds the headboard against the ground at the collar of the rock hole and puts the bolt in tension. The second slot is aligned 90" from the plane of the first slot to avoid Longitudinal splitting and is notched out slightly to allow easier insertion of the collar wedge after the bolt has been driven to bottom. To prevent splitting the headboard by spreading action of the head wedge, this slot is oriented at 90" to the grain of the headboard when the pieces are assembled, Fig. 2. The wedges are similar to standard mine wedges, but more slender; they are cut 1 7/8 in. wide and 1 in. thick at the heel and taper out in 16 in. of length. The headboard, or bearing plate, is not necessary for some types of ground but generally is desirable because it helps the bolt to support an area of loose, friable rock and reduces the tendency for the rock at the collar of the hole to split away from the wedged head by distributing the pressure over a wider rock surface. The headboard may be a 24-to 30-in. length of 3-in. plank, 8 to 12 in. wide, but a similar length of rounded sawmill slab serves equally well at 20 pct of the cost. A hole of 2-in. diam is bored or punched through the center of the headboard, either at 90" or at various high angles to its surface. The bolt is inserted to its shoulder through this hole, then driven into the rock hole. Bolts, wedges, and headboards are given a full timber preservative treatment to inhibit rot. Bundles of each are immersed in a warm saturated solution of Osmose salts in water for 48 hr, removed, dripped dry, and stored in a relatively humid underground depot to cure. Most wooden rock bolts used by Day Mines are 4 ft long. Holes to receive them, about 42 in deep and 2 1/8 in. in diam, are drilled into the rock' to be supported, nearly normal to the periphery of the mine opening. The type of drill used is dictated by convenience: stoper, jackleg, or jumbo-mounted drifter. Correct depth of the hole is assured by use of a measuring stick that has been cut to the proper distance from drill chuck to the ground at the collar of the hole when a standard length drill rod is at the bottom. The bolt is seated to the shoulder through the hole in the headboard, the foot-end wedge is placed in its slot, and the assembly is inserted into the rock hole. Then the bolt is driven until it is seated solidly on the wedge against the bottom of the rock hole. Driving may be by hand with a sledge, or

Jan 1, 1954

By Gerald, Sherman

INCREASED production and con¬sumption of all metals, indicate the progress of industry toward that condition formerly thought to be normal. With no market limitations on silver and gold the two new precious-metal mines, the Silver Queen (now the Golden Queen), in southern California, and the Sunshine, at Kellogg in northern Idaho have made progress toward a high routine production. The Golden Queen 300-ton mill is finished and ready. The Sunshine mill has been enlarged and production is now at the rate of 500 tons per day of high-grade silver ore. The Hecla Mining Co. is developing the Polaris vein, which should be the extension of the Sunshine to the east. Some rich ore is reported. The developments of the' East African Gold Fields, Ltd., in the Lupa gold field of Tanganyika Territory, have made good progress, but operation in an isolated locality is not rapid and a large plant will be required. There have been no other discoveries reported that can be compared with the three mentioned, but production has increased, with greater capacity in dredging equipment and underground mines more adequately prepared for production.

Jan 1, 1936

The fifth convention of the National Foreign Trade Council was held in Cincinnati, Apr. 18, 19 and 20. More than one thousand accepted delegates were registered, the American Institute of Mining Engineers being represented by W. L. Saunders and W. N. Thayer. The convention was called to order Thursday morning, Apr. 18, in the convention hall of the Hotel Gibson; by the Chairman, Mr. James .A. Farrel, president of the U. S. Steel Corporation, and was in continuous session for two clays, several group sessions being held simultaneously. The convention adjourned Saturday morning after receiving the report of the central committee. The dominant themes of the convention were: First, "Win the War" and second, "Establish Foreign Trade on a. Firmer Basis." The discussions included textiles, lumber, chemicals, automobiles, finance, and agriculture, and also those things in which mining engineers are particularly interested, metals, oil, and coal. The report of the central committee, which was adopted, recommended the stimulation' of production of all materials required for war purposes; the subordination of all trade that will not impose new and heavy penalties on our adversaries; the maintenance of such foreign trade as will support national credit and supply materials required for military and naval purposes; the continued interchange so far as possible of merchandise and products between the United States and. Latin-America, Asia and Oceania; the immediate increase of tonnage in the north Atlantic; the cheerful and whole-hearted cooperation of importers

Jan 6, 1918

By R. F. Mehl, B. Lustman

THE formation of intermediate phase layers in cementation processes has been subjected to extensive qualitative investigation though to relatively little quantitative study; this work has recently been fully summarized by F. N. Rhines.1 It is necessary here only to enumerate the general conclusions drawn concerning the kinetic laws governing the growth of intermediate layers and to state what is known concerning the structural changes accompanying the generation of phase layers. I. When the intermediate phase is protective in type-i.e., when its density is less than that of the base metal, so that a continuous coating is formed and maintained-the isothermal growth of the phase follows a simple parabolic equation: [1 = ki [I]] where X is the thickness of the alloy layer, k the reaction rate constant, and [t] the time. The applicability of this equation to diffusion processes is tested by plotting the square of the thickness versus time, or by plotting the thickness versus the square root of time; the resultant achievement of a straight line in such a plot has been considered sufficient proof of the validity of this equation. Exceptions have been found where liquid phases are involved in the reaction, where the diffusion layer is cracked,2 and where thin semimetallic oxide and sulphide coatings are formed on metals.3 In the first two cases the thickness increases linearly with time, and in the latter it is a logarithmic function of time. 2. The rate of thickening varies with temperature according to the Arrhenius equation: [k = Ae-QIRT [2]] where k is the parabolic rate constant of Eq. I, or some other rate-descriptive function, A is the action constant, e the base of natural logarithms, Q the heat of activation, R the gas constant, and T absolute temperature. This equation has been found to be generally valid except when transformations occur during reaction in either the base metal or in the reaction layer; in such instances Eq. 2 is still applicable with different values for the constants A and Q above and below the transformation temperature. 3. All phases that are stable at the temperature at which diffusion occurs will appear in the interdiffusion of two components. In some cases certain of the phases may be too thin to be observed and identified easily. Nonequilibrium phases have never been noted in thick reaction layers; i.e., layers of a thickness that may be discerned microscopically. The relative thickness of each phase in a diffusion layer is proportional to the concentration gradient and to the rate of diffusion in that phase.4 The reaction layers tend to have a

Jan 1, 1942

By Walter R. Hibbard, George H. Eichelman, William P. Saunders

INTEREST in the various products of the austenite eutectoid transformation in iron-carbon alloys, particularly as produced by the isothermal sub-critical techniques introduced by Davenport and Bain,1 has resulted in the application of similar heat treatments to other eutectoid transformations. Studies2.3.4 of the beta copper-aluminum alloy eutectoid transformation revealed microstructures very similar to those found in iron-carbon alloys. Investigations5,6 of the kappa phase in the copper-silicon alloy system have established the eutectoid type transformation of this phase into terminal alpha and intermediate gamma phases. This transformation has been reported' as forming a eutectoid type structure in a very sluggish manner by a long time isothermal treatment. The purpose of the present investigation is to study the products of the kappa eutectoid transformation as affected by transformation temperatures by means of microscopic and hardness methods. PREPARATION OF ALLOYS The copper-silicon alloy equilibrium diagram is shown in Fig I. The kappa field converges to a minimum silicon solubility at the eutectoid composition and all other completely kappa alloys are hypereutectoid. Thus, kappa decomposition involves first the proeutectoid precipitation of gamma, followed by the eutectoid transformation of a lower silicon content kappa (5.2 pct). Smith5 has indicated that alloys containing between 5.4 and 5.7 pct silicon could be hot rolled, but that the latter composition was desirable in order to permit a wider kappa temperature range. The alloy was prepared by adding Baker's commercially pure silicon to an ingot of copper-silicon alloy containing 2.34 pct silicon remaining from the investigation of Brick, Martin and Angier.7 Following the casting techniques of Krynitsky, Saunders and Stern,8 the ingot was melted under a heavy layer of dried charcoal in a clay-graphite crucible in a gas-fired pot furnace. Small lumps of silicon were held under the melt surface with a graphite rod. After the silicon had dissolved, the alloy was chill-cast and then remelted without a cover, stirred thoroughly, skimmed and poured into a preheated cast iron mold. The cast microstructure is shown in Fig 2. The casting, 10 X 4 X ¾ in., was annealed at 750°C for 21 brand furnace cooled. About 1/16 in. was milled from all surfaces. The plate was cut in half longitudinally and the bottom half analyzed by A.S.T.M. methods.9 The composition by weight was as follows: copper 94.24 pct, silicon 5.56 pct, iron 0.11 pct.

Jan 1, 1948

By Thomas F. Bates

ANALYSIS of the chemical and structural differences in minerals often results in a better understanding of the differences in the geological conditions under which they were formed. The minerals in the kaolinite group differ in the amount of interlayer water and in the nature and amount of ordered and/or random shifting of each 1:1 layer with respect to those above and below it. This paper is a progress report resulting from research on the morphology, structure, and origin of fine-grained minerals, supported by Contract N6onr26914 with the Geophysics Branch of the Office of Naval Research. The purpose of the paper is to present data obtained in the laboratories at The Pennsylvania State College and elsewhere, which reveal some of the details of structure of the minerals in the kaolinite group, and to suggest a number of interpretations that bear upon the conditions of origin of these minerals. Be¬cause most of the work in this investigation thus far has been concerned with the relationships of kaolinite, halloysite (4H2O; endellite), and halloysite (2H2O), must of the discussion deals with these members of the group. The first step in the analysis of the differences in two sets of geological conditions is an evaluation of the differences in the minerals that result. Thus the chemical differences between the montmorillonite and the kaolinite clays corroborate other evidence in support of the view that the montmorillonites are commonly formed when solutions are alkaline and leaching poor, while kaolinite usually is associated with acid solutions and good drainage condi¬tions. It is obvious that the greater the differences in the minerals, the more divergent may be the conditions that give rise to them and the more readily one condition can be distinguished from the other. In the kaolinite group, differences between individual members are small, therefore the differences in condition of origin are presumably subtle and difficult to define. At the same time, the very fact that the minerals differ only slightly makes them more sensitive indicators of the exact conditions under which they and the minerals associated with them were formed. Since clay minerals are being used more and more to evaluate the nature, value, and mode of formation of economic mineral deposits, an attempt to define these subtle differences would appear worth while. For purposes of the present discussion, the minerals nacrite, dickite, kaolinite, the so-called "fireclay mineral," halloysite (4H2O), halloysite

Jan 1, 1952

By S. Yukawa, M. J. Sinnott

A high resolution autoradiographic study of the diffusion of a nickel isotope (NP3) into copper in the temperature range of 650° to 925°C, with particular emphasis on grain boundary diffusion, has been made. The extent of grain boundary diffusion is a function of the grain boundary angle and the diffusion temperature. The ratios of the grain boundary diffusion coefficient to the lattice diffusion coefficient ranges from 104 to 105. The activation energy for grain boundary diffusion decreases with increasing grain boundary angle. STUDIES and reviews&apos;-8 of metallic diffusion have indicated that grain boundary diffusion is a common phenomenon but quantitative studies of the many variables involved are not numerous. The present work was concerned with determining the influence of the crystallographic orientation of the grain boundaries and the temperature on the extent of boundary diffusion of nickel into copper. The study involved essentially three steps: 1—the production of grain boundaries of known crystallographic orientation, 2—the determination of the extent of diffusion into the boundaries, and 3—the analysis of the resulting data in terms of the usual diffusion concepts. The grain boundaries investigated approximated the simple tilt variety having l° of freedom. They were produced by controlling the solidification from a melt of Cuprovac (a high purity vacuum-melted copper obtained from Vacuum Metals Corp.) of a pair of seed crystals so that the bicrystals of copper produced had a common <100> axis. By rotating one seed crystal relative to the other, a simple tilt boundary was produced. The angle of rotation between the two crystals is the grain boundary angle 8, or what is sometimes termed the misfit angle. In all, some 16 boundaries ranging from 2" to 72" in 5" to 10" steps were investigated. The crystallographic orientations were measured with the use of both X-ray and optical goniometric techniques. The <100> axes in the crystals were found to be parallel within 2" to 3" with the exception of one crystal (8 = 12") in which the axes were 6" from being parallel. All bicrystals showed evidences of sub-grain structures. Laue analyses showed that these subgrains differed in orientation up to a maximum of 2". Because of these variations, and some curvature in the boundaries, the grain boundary angles listed are actually average values and deviate from the 1 o of freedom boundaries. The stripping film technique of high resolution autoradiography was used to detect the diffusion of the nickel isotope into the grain boundaries of the bicrystals of copper. Kodak experimental permeable stripping film with an emulsion layer 5 u thick

Jan 1, 1956

By T. Koulomzine

The theory of the Askania mag-netometer, as well as a complete discussion of all factors influencing magnetometer readings, is very ably described by J. Wallace Joyce.1 We will assume that the reader is thoroughly familiar with this theory and we will use whenever possible the same notations for the physical values involved in the theory. On the other hand, we believe that the principal formulas of the magnetometer can be deduced much more easily by the use of differential calculus than by the methods employed by Joyce. Consequently, we are presenting herewith a resumé of the theory of the vertical magnetometer in order to determine the correct formula of the temperature coefficient which we propose to compensate. Short Theory of the Vertical Magnetometers We shall accept the following notations: m = total mass of the magnet system, in grams. g = acceleration of gravity, in dynes. a = projection on the axis of the magnet system of the distance between the axis of support and the center of gravity of the magnet system, in centimeters. h = projection on the perpendicular to the axis of the magnet system of the distance between the axis of support and the center of gravity of the magnet system, in centimeters. M = 2pL = M, magnetic moment of the magnet system. Z = vertical component of the earth&apos;s magnetic field. ? = deflection angle of the magnet system. = focal length of objective lens in the optical system S = scale reading. In a vertical magnetometer the axis of the magnet system is kept horizontal within 2". Therefore, referring to Fig 1, we see that the magnetic torque of the magnet system influenced by Z must be counterbalanced by the gravity torque. MZ cos ? = mga cos ? + mgh sin ? or dividing by cos ? MZ = mga + mgh tan ? If we now move to another magnetic station and the temperature conditions change, the values of all the variables will change also: M, a, and h under the influence of temperature. 2, both with time and space. ? and S, as a result of all the above changes. Taking increments in Eq 2 we obtain: (Mo + ?M)(Z + ?Z) = mgao + mg?a + mg(h + ?h) tan (? +??) but tan (? +??), because ? is small, can be replaced by tan ? + tan ??; in fact tan (?+ ??) = sin ?.cos ?? + cos ?.sin ??/ cos ?.cos ?? — sin ?sin ?? but sin ? sin ???0 tan (8 + ??) ? tan ? + tan ??. Fur-thermore, neglecting all terms of the equation containing two differentials becomes: or a differential and a tan ??, Eq 3

Jan 1, 1950

By A. S. Joy

Vacuum flotation tests carried out according to the method of Schuhmann and Prakash1 have shown that the acid limiting edge of the flotation area for a Brazilian hematite, in the presence of dodecylamine, is a straight line of slope approximately unity. The flotation tests and the structure, surface ionization, and electrokinetic properties of this hematite have been fully discussed elsewhere. 2 The numbers of adsorbed H+, and OH- ions and collector molecules have been determined in the range of critical conditions defining the acid limit of the flotation area. The total amine adsorption is shown in Fig. 1 as a set of contours superimposed on the straight part of the flotation area. These were determined by spectro-photometric estimation of the complex formed between residual amine and the anionic dye Orange II.3 The ionic strength of the solutions was kept constant and at a value in sufficient excess of the amine concentration to ensure that the diffuse part of the double layer was populated predominantly by indifferent ions. Adsorption of H+ and OH- in the absence of amine was found by potentiometric acid-base titration in the presence of hematite.4 The form of the adsorption-titration curves suggested that the hematite surface behaves in an amphoteric manner, and that positively charged sites arise through loss of a hydroxyl ion, and negatively charged sites by loss of a hydrogen ion. On this basis, curves 8 and 9, shown in Fig. 2, were calculated from the titration curves. These show the variation of the numbers of positive (s +) and negative (s—) sites with pH. To distinguish between ionic and other modes of adsorption, zeta-potential determinations have also been made using the streaming potential technique. The influence of amine on the zeta-potential of the mineral over a wide pH range is shown in Fig. 3. The change in charge ?s, due to adsorption of amine ions in the Stern layer, was calculated by applying the Gouy-Chapman theory, as modified by Stem, to the results shown in Fig. 3. The validity of this treatment has been shown by Ottewill and Jaycock.5 The three full lines, Nos. (1) through (3), included in Fig. 2 show the relationship between ?s and pH at three amine concentrations. The general conclusion from the zeta-potential curves is that adsorption of amine causes a reduction in the negative charge on the surface. Comparison of the values shown in curves (1) through (3) of Fig. 2 with the - curve shows that the magnitude of the reduction is comparable with that of s - at any given

Jan 1, 1964

By Gerald Edmunds

In a paper1 before this Institute in 1940, the writer reported that the surface orientation texture of zinc and cadmium differed from the texture existing within the casting, in that basal planes were parallel to the surface. He was unable to rationalize the , origin of this surface texture. It is conceivable that the surface orientation texture is influenced by the atomic force fields, which are different at the surface and within the body of metal. It was considered that a radical changc in the surface against which the metal is cast might alter the surface texture. In trial of this, zinc has been cast against a surface of molten lead, but the same result has been obtained—i.e., (001) parallel, ± 2oo, to the surface—as was obtained when it was cast against air, Transite or iron.&apos; Into the bottom of an open cast-iron tray, 7 by 14 in. by 2 in. deep, preheated to about 275°C., about 1/4 in. of lead, then 1/2 in. of zinc was poured, and the whole was covered with an electric heater to enforce freezing from the bottom upward. After a lapse of time sufficient for the zinc but not the lead to solidify, the zinc slab was raised free of the molten lead. The bottom surface of the zinc casting was coated with a thin layer of lead. A specimen of the slab 136 in. square was metallographically polished to flatten it and remove the slight film of lead, and the orientation was determined by the method used before,&apos; with the result stated above. Some determinations have also been made on other metals, as follows: Surface orientation determinations were made on the 3/8-in. diameter grip section of two 1/4-in. diameter aluminum-alloy die-cast tensile bars and on a 1/8 by 1/2-in. flat aluminum-alloy die-cast tensile bar. None of these three aluminum die castings exhibited any preferred orientation at the surface. A brass die casting (nominal composition: 60 Cu, 37.75 Zn, 1.00 Sn, 1.00 Pb, 0.10 Al, 0.15 Si) furnished by C. S. Smith was also examined. The surface showed a random orientation of alpha and beta. Summary A zinc casting solidified against a molten lead surface was found to have the same surface orientation texture, (001) parallel to the surface, as other zinc and cadmium castings. Aluminum and alpha-beta brass die castings were found to have random grain orientation textures at the surface. Acknowledgment The X-ray determinations were conducted by M. L. Fuller.

Jan 1, 1945

By G. H., Wigton

THE present milling operations of the Chief Consolidated Mining Co. consist- of flotation of oxidized minerals from siliceous ores of the Tintic Mining district, Utah. As the lead, silver, and gold minerals that give the ores economic value are almost entirely oxidized; their successful flotation has necessitated the solution of many new problems. Laboratory effort resulted in the selection of a, natural float for the oxidized minerals. &apos;By "natural float," I mean that no reagent was added to produce a sulfide film on the osidized minerals before or while subjecting them to flotation operations. As compared to methods involving sulfide filming, the natural float was selected because it promised successful treatment of a larger variety, of ores without change in quantity or kind of reagents, as well as a better economic balance between metal recovery and concentration ratio. In explanation, I can, state that with sulfide filming, the efficiency of the method decreases rapidly with increase of hydrated, iron osides in the ore, whereas with the natural float the same effect has not been noted. Evidence shows that although sulfidizing can produce greater metal recoveries, it yields a concentrate so much lower in grade that no advantage results.

Jan 1, 1928

By Fred B. Brost

In 1976, a decision was made to install a conveying system to transport ore 10.3 km (6.4 miles) from the new Eisenhower mine to Twin Buttes. The system, supplied and installed by Cable Belt Ltd., of England, represents a radical departure from conventional conveyor systems. The driving tension is applied through two endless wire ropes while the belt acts only as the carrying medium. Features of the system are a single 2240-kW (3000-hp) drive and a 60° angle bend. Construction was completed in two years and full production was attained alter several mouths operation.

Jan 12, 1979