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By Frederic E. Carter

There have been many attempts to prove that platinum was known to the ancients, but since no traces of the metal have been found in the relics of early times, it must be concluded that it was not known to them. As far as records go, it was actually first discovered in the 16th century in a Spanish mine on the Pinto River in South America; from which source it received its name of Platina del Pinto (little silver from the Pinto). It was more or less of a rarity and was a subject of interest to a few chemists only, until the year 1822 when the metal was first discovered in Russia. In 1819 there were noticed in the washings of the gold sands of the southern part of the Ural Mountains, grains of a heavy white substance, but it was not until three years later that this substance was found to contain platinum. While at first the amounts of platinum brought from the Urals were meager, prospecting soon disclosed rich deposits extending over a considerable area, and nuggets from 10 to 20 lb. were by no means rare. This discovery assured to chemists an ample supply of platinum for their crucibles, etc. The ore is now found in various parts of the world but the richest deposits are still found in the Ural Mountains. The platinum of commerce is obtained entirely from alluvial deposits at depths varying from 6 to 40 ft. The sand and gravel of former river beds are subjected to a series of screenings and washings to effect the separation of the ore. Actually, probably all gold-bearing gravel beds of the world contain platinum, and it is more than likely that large quantities of platinum ore have been thrown away with the black sand washings from gold placer deposits. This is especially true of the alluvial deposits of the Pacific Coast in California and Oregon. Platinum ore is usually found in the form of rounded or flattened grains of "sand," and occasionally in irregular lumps of the size of peas. Large nuggets are very rare. The ore has a metallic luster and is distinguished by its steel gray color, but shows light gray streak when rubbed on a hard white surface; it has a high specific gravity, 16 to 19; is infusible in the hottest blast furnaces, and insoluble in any single acid. Platinum ore is a complex body consisting of the metal in combination with varying proportions of the other members of the platinum group; iridium,

By George P. Chapman

Mica is a platy mineral occurring in a variety of complex hydrous aluminosilicate forms with differing chemical composition and physical properties. Principal minerals in the mica group include: Muscovite-potassium mica (colorless or pale green/ ruby) Phlogopite-magnesium mica (dark brown or amber) Biotite-magnesium-iron mica (black or dark green) Lepidolite-lithium mica (lilac) Selected properties are given in Table 1. Muscovite is most important commercially with phlogopite of lesser use. The laminated structure of mica enables it to be split into very thin films which are transparent and tough as well as having outstanding dielectric and insulating properties. Commercially, mica is used in a number of forms (Chowdbury, 1941; Rajgarhia, 1951; Skow, 1962). Sheet mica consists of flat sheets mined from naturally occurring books of mica, free from defects and capable of being punched or stamped into required shapes. Sheet mica is separately classified into blocks, films, or splittings according to thickness. Built-up mica, or micanite, is made by arranging overlapping splittings in layers , cemented with a binder and pressed together at high temperature. Reconstituted mica, or mica paper, is made by depositing fine flakes of high-quality scrap mica in a continuous film impregnated with binder. Scrap and flake mica are normally unsuitable in quality or size for making sheet mica. Originally the term scrap mica referred to the waste byproduct of mining and fabricating sheet mica, and distinct uses were developed for this material. Subsequently it became economically feasible to mine lower quality mica for these uses, and the term flake mica was introduced. Although the two terms are still used somewhat synonymously, it is considered better, at least in the United States, to use the term flake mica in referring to mica mined for uses other than as sheet mica; and to restrict the term scrap mica to mica mined for or with sheet mica, but which will not meet the specifications. Synthetic mica, such as fluorophlogopite, is produced by slow crystallization of a melted blend of pure raw materials. Mineralogy In the true sense the term mica does not relate to, a particular mineral, but to a group or family of minerals of similar chemical composition and to some extent similar physical properties. These minerals are predominantly potassium aluminum silicates with varying amounts of magnesium, iron, and lithium. The precise formulas and isomorphic relationships of the various group members have been studied, but general agreement has not been reached (Grimshaw, 1971; Hurlbut, 1952; Skow, 1962). The general formula describing the chemical composition of micas is [X2Y4-6Z8020(OH, F)4, where X is mainly K, Na, or Ca; Y is mainly Al, Mg, or Fe; Z is mainly Si or Al (Deer, et al., 1962).] These minerals have an internal structure of the layered lattice type where the silicon atoms are in the center of a tetrahedral grouping of oxygen atoms. The groups are linked together in a single plane by three oxygen atoms that lie within the common plane. Each of these oxygen atoms is shared by two tetrahedra. These linked tetrahedral groups, when continually extended, produce a hexagonal network within the plane. This internal structure of the mica has been used to explain the ex-

Jan 1, 1983

By E. C. Pechin

AT the suggestion of some members of the Institute, attention is called to the record of the working of Dunbar Furnace during the twelve months ending in January, 1874. During this period, with a product of over eleven thousand gross tons, not a single ton of

Jan 1, 1874

By Claudio Guarnaschelli

Alteration of the electronic distribution of mineral surfaces by light irradiation has been used to modify the adsorption characteristics of flotation reagents. Energy of a few electron volts is suficient to cause the necessary transitions that either enhance or retard the adsorption phenomenon. The adsorption characteristics of potassium ethyl xanthate on galena and marmatite are presented as functions of the energy of illumination, type of semiconductor, and surface oxidation. In dilute solutions, the adsorption differences are readily detected by controlled kinetic measurements. The correlation between the electronic distribution and the adsorption and desorption phenomena at the solid surface is gaining more attention and acceptance. These interrelations have found a practical application in mineral processing since all of the sulfide minerals display semiconducting properties. By varying the ratio of free electron to electron vacancies, the separation of ilmenite from rutilel and zircon from pyrochlore" has been executed successfully. Plaksin et al.' indicate three possible ways of utilizing the semiconductor properties of a mineral. The first one involves the control of the oxidation-reduction potential of the liquid phase, the second one consists of allowing selected additives to diffuse through the mineral surface, while the third one entails a change in the adsorption and chemical activity of minerals by irradiating their surface. The aim of the present work is to consider the effect of irradiation on the adsorption-desorption characteristics of natural minerals. Since the effect of irradiation is to change the electronic distribution at the surface:

Jan 1, 1971

[VOL. XXXVI. Page. Line. 155 29 For "Joachimstahl," read "Joachimsthal." 215 Foot-note 2. For " May, 1892," read " May, 1902." 216 21 For " ack-screw," read " jack-screw." VOL. XXXVII. 31 3 For "quantity of tons," read "quantity of slimes." 35 10 Expunge "recorded in Table VII." 37 24 Expunge "to." 38 33 For "page 89," read "page 9." 44 40 For "page 86," read "page 6." 47 In table, third line under heading "Excavators and Conveyors," expunge "per 40 ft. of."]

Jan 1, 1918

By Walter C. Smith, O. J. Seeds

METALLIC bismuth was known in the Middle Ages and the name is supposed to come from the German Wismut. The origin of the German name is uncertain. References to bismuth are found in the writings of Valentine, Paracelsus, and Agricola between 1450 and 1550. Early specimens of bismuth were very impure and often were confused with antimony, tin, and zinc. About the middle of the eighteenth century, J. H. Pott, C. J. Geoffroy, and Torbern Bergman succeeded in producing fairly pure bismuth and showed it to be an elementary metal similar in many respects to lead. H. S. Washington has estimated that bismuth occurs in the earth's crust about as abundantly as tungsten and silver; i.e., to the extent of 10-6 or 10-7 pct. It is found as native metal, both alone and associated with tin, copper, and other metals, and in a large variety of ores. The important ores are the sulfide (bismuthinite), the oxide (bismite), and the carbonates (bismutite and bismutosphaerite) . Other occurrences of bismuth are in the vanadate (pucherite), the selenide (guanajuatite), the telluride (tetradymite), and in many complex sulfides, arsenides, and antimonides. Bismuth minerals have been found in many parts of the world but very few of the bismuth deposits have been of economic value, the oxide ores from parts of China being the exception. The major portion of the bismuth production of today is the so-called by- product bismuth. Bismuth often occurs in ores mined and treated primarily for other metals, and during the treatment of these ores

Jan 1, 1953

By Seymour G. Epstein

Using a modified capillary-reservoir technique, electromigration of dilute solutions of silver in liquid bismuth has been measured with relatively good precision. The effects of experiment duration, temperature. current density, and silver concentration have been investigated. Chemical diffusion coefficients of silver in liquid bismuth were also measured at temperatures ranging from 300°to 600°C. The effective valence of silver in bismuth was calculated as a function of temperature from a comparison of electric mobilities and diffusion coefficients. In an alloy containing 1 wt pct Ag, the electric mobility of silver increased from 1.65 x X sq cm per v-sec at 300°C to 2.38 x 10-4at 600°C; the diffusion coefficient in-creased from 3.0 to 17.5 x 10-5 sq cm per sec over the same temperature range. Calculated values of effective valence decreased from 0.28 at 300°C to 0.10 at 600°c. ALTHOUGH there has been considerable progress in the theoretical treatment of electron-transport properties in liquid metals, the mechanisms of mass-transport phenomena in liquid metals are still not clearly understood. This is especially true for the case of electro migration, alternatively termed elec-trotransport or electrodiffusion, which is mass transport induced by an applied electric field. A thorough knowledge of the mechanisms governing electromigration will considerably aid in understanding the electronic state of an impurity atom in a liquid metal. Electromigration has been long observed and studied in liquid metals and alloys. However, no satisfactory theory to explain the observed effects has been developed. The disparity in the present theoretical treatments, summarized by Verhoeven,1 has been attributed to the difficulty in describing the momentum transfer between electrons and ions and to the lack of precise measurements in liquid metals, especially at elevated temperatures. Prior to the last decade most of the electromigration studies were qualitative, in that only the direction of migration of alloy constituents was determined with any degree of reliability. These results have been summarized by schwarz,2 who was able to measure the electric mobility of several elements in mercury. More recently electromigration in liquid metals has been measured by a variety of techniques, with a varying degree of success. Mangelsdorf3,4 made precise measurements on dilute amalgams at room temperature, using a technique relating changes in composition to changes in alloy resistivity, but was unable to make measurements at elevated temperatures. Using a modification of this technique, Verhoeven and Hucke5 measured electromigration and resistivities in liquid Bi-Sn alloys. However, the resistivity technique is not sensitive to small composition changes and is impractical for very dilute alloys. Verhoeven and Hucke6 also measured electromigration of several solutes in liquid bismuth by adapting the capillary-reservoir method for determining diffusion coefficients in liquids. The reported precision of these measurements was poor, however, primarily due to the large uncertainties in the chemical analyses to determine concentration changes. Belashchenko7 has summarized the recent Russian investigations of electromigration, many of which, however, are of questionable accuracy. The present study was initiated to develop an experimental technique which would be both versatile and sufficiently sensitive to yield precise measurements of electromigration of solutes in dilute metal alloys at elevated temperatures. Using this technique, a comprehensive study of silver in liquid bismuth was made to determine the effects of experimental variables on the apparent electric mobilities. Chemical diffusion coefficients of silver in liquid bismuth were also measured over the same temperature range for comparison with the electromigration data. EXPERIMENTAL TECHNIQUE Electromigration Measurements. Electromigration of silver in liquid bismuth was measured by the capillary-reservoir technique, similar to that used by Verhoeven and Hucke,6 but modified to yield more

Jan 1, 1967

By O. D. Gonzalez, H. A. Wriedt

Alloys ranging from pure iron to pure nickel were saturated with nitrogen gas at 918°, 999°, and 1217°C and analyzed. The solubility of nitrogen at 1-atm pressure was obtained as a function of nickel content for the whole range of iron-nickel alloys and the temperature dependence of solubility is shown for the experimental alloy compositions. The heat of solution and the entropy of solution of nitrogen in the alloys as func-tiom of composition up to 41 pct Ni are given. 1 HE acquisition of more exact thermodynamic information for systems composed of iron with various alloying elements continues to interest ferrous metallurgists. The interstitial alloying elements, especially carbon, hydrogen, and nitrogen, comprise a field of particularly intense study. A recent investigation of carbon solubility in Fe-Ni alloys held at 1000°C in gases of fixed carbon activity showed an unpredicted minimum in the solubility near 72 pct Ni.1 The present investigation was undertaken to see if a similar anomaly in solubility existed for nitrogen in Fe-Ni alloys. The solubility of nitrogen in ? iron at known nitrogen activities has been measured several times.&apos;-&apos; Corresponding information for the solubility of nitrogen in solid Ni and Fe-Ni alloys is not available. Juza and sachsze9 reported that metallic nickel dissolved 0.07 pct N in equilibrium with Ni3N at 445°C. This result was regarded as dubious by Turkdogan and Ignatowicz10 who found less than 0.0004 pct N in nickel specimens equilibrated at 600°C with ammonia-hydrogen mixtures having fugacities of N2 gas up to 35,000 atm. Such fragmentary reports indicate only that nitrogen gas has a very much lower solubility in nickel than in iron. MATERIALS A purified iron from Battelle Memorial Institute was used for solubility measurements. This grade contained more than 99.95 pct Fe, the highest content of any measured individual impurity being 50 ppm for each of As, C, Cu, and Pb. The nickel and iron-nickel alloys, supplied by the International Nickel Co., contained 0.02 to 0.04 pct C, 0.17 to 0.19 pct Mn, 0.04 to 0.08 pct Si, < 0.01 pct P, <0.03 pct S, and <0.20 pct Co as principal impurities. The Fe-0.59 pct Mn alloy was of zone-melted quality, the highest concentration of any individual impurity being 15 ppm Al. The "prepurified" grade of nitrogen gas from Matheson Co. had a nominal nitrogen content of 99.996 pct. An "electrolytic" grade of hydrogen gas from National Cylinder Gas. CO. in which the principal impurity is water vapor was admixed with the nitrogen to prevent oxidation of these specimens. This grade was preferred to a purer grade because the presence of some oxygen helps in suppressing contamination of the specimens, for instance, by silicon from the porcelain furnace tube. EXPERIMENTAL PROCEDURE The specimens were equilibrated in vertical tube furnaces through which a 99 pct N2-1 pct H2 gas was passed at ambient pressure. For the 915", 918", and 999°C runs, a wound-resistance furnace was used, and for the 1217°C runs, a furnace with a tubular silicon carbide element was used. The temperature control system on both furnaces was similar: a Weston "Celectray" controller with a modulator, responding to the electromotive force of a thermocouple with its hot junction in the furnace, switched the furnace current between high and low settings. The temperature distributions in the working zones of the furnaces were determined with calibrated Pt/Pt-10 pct Rh thermocouples. The overall uncertainty in temperature was estimated to be ±3° at 915° to 999°C and ±5° at 1217°C . Consideration of the small temperature coefficients of the equilibria studied, together with the error limits in the method of analyzing for nitrogen, showed that further refinement in temperature uniformity would give no improvement in resultant accuracy. The reactive gas was generated by mixing together "prepurified" nitrogen and "electrolytic" hydrogen directly from cylinders commercially supplied. The flow rates of nitrogen and of hydrogen were fixed by setting with bleeders the pressure drops across the individual calibrated flow meters of constant resistance. For any given alloy, the solubility of nitrogen at 1-atm pressure (% N) was obtained from the analyzed nitrogen content of equilibrated specimens (% Na)according to Sieverts&apos; law, thus

Jan 1, 1962

By R. W. Cahn, C. D. Graham

Two predictions of the oriented growth theory of recrystallization textures have been tested by measuring the orientation dependence of the rate of growth of a single grain into a strained single crystal of aluminum, and determining the orientations of artificially and spontaneously nucleated grains growing preferentially into strained aluminum single crystals. Growth rates are found to be insensitive to orientation, except that new grains with orientations similar to the matrix or to a twin of the matrix have very low mobilities. Similarly, new grains growing preferentially into a strained crystal have random orientations, except that orientations near that of the matrix or its twins are avoided. The predictions of oriented growth theory are thus not confirmed. BASICALLY, the oriented growth theory of re-crystallization textures1 rests on the assumption that the rate of growth of a recrystallizing grain depends strongly on the orientation of the growing grain relative to the strained matrix into which it grows. In particular, the theory holds that in face-centered-cubic metals the orientation which corresponds to maximum growth rate is one in which the growing grain and the matrix are related by a rotation about a common <111> direction. The amount of rotation, as derived from several kinds of experiments,2-1 has been assigned various values, generally in the range between 20" and 40". (A <111> rotation of 60" is a twin relationship.) The conclusion that boundary migration rates depend strongly on orientation is based almost entirely on indirect evidence; there have been very few direct measurements of boundary migration rates as a function of orientation.* " The present investigation was undertaken to provide such measurements, to help make possible a decision between the oriented growth and oriented nilcleation theories of recrystal-lization textures. The basic experimental program consisted of measuring the rate of growth of a single recrystal-lizing grain consuming a strained single crystal, with the orientations of both grains preselected so that the effect of orientation on growth rate could be determined. A prerequisite for such an experiment is a strained single crystal which will support the growth of a new grain but which will not spontaneously nucleate new grains on heating. That is, the crystal must support the growth of a grain nucleated artificially, but contain no recrystalliza-tion nuclei which will become active at the testing temperature. Beck was apparently the first to note that such a condition could exist," and to make use of the condition for am experiment of the type described here.&apos; The present work was actually suggested, however, by a report of Tiedema". " that an aluminum single crystal strip, oriented with a (111) plane in the plane of the strip and a < 112> direction parallel to the tensile axis, would not recrystallize after 20 pet extension even when heated almost to the melting point, provided that the strip was heavily etched before being heated. This result could not be duplicated in the present work. In fact, it was found that any crystal which deformed in multiple slip (<100>, <112> and <111> orientations) underwent spontaneous nucleation after 15 pet extension, even if etched. However, crystals which deformed in single slip, and which did not develop heavy deformation bands, could be extended 15 pet without showing spontaneous nucleation at temperatures up to 600°C. Crystals oriented within about 10o of <110> which developed heavy deformation bands could be extended 10 pet without showing spontaneous nucleation. In all cases a heavy etch was required to prevent nucleation. Etching was necessary because of the presence of an oxide layer on the crystal surface at the time of straining, which leads to preferential nucleation at the surface.&apos;&apos; Grain Growth Rates Experimental Procedure and Results—Aluminum strips of 99.6 pet purity (principal impurities 0.19 pet Fe and 0.12 pet Si), 1 mm by 1 cm in cross section, were grown into single crystals of controlled orientation by the strain-anneal method of Fuji-wara.&apos;"&apos; " A sharp temperature gradient was maintained in the strips during growth by lowering them into a salt bath controlled at 650°C. Crystal orientations were determined by the etch-pit method of Barrett and Levenson" to an accuracy of ±2O. The crystals were extended by 10 or 15 pet in a simple hand operated tensile machine. Crystal orientations were rechecked after extension, and were found to be in agreement with the orientations predicted by the formula of Schmid and Boas." After extension, the grip ends of the single crystal specimen were cut off with a jeweller&apos;s saw, and the crystal heavily etched (at least 20 pet wt loss) in hot 10 pet Na or KOH solution. A region of severe local deformation was then introduced at one corner of the strip, usually by cutting off the corner with shears. Heating this end of the strip caused a large number of new grains to nucleate at the sheared edge. One of these grains grew to occupy the full width of the strip. The appearance of the strip at

Jan 1, 1957

By K. E. J. Rapperport, C. S. Hartley

The only slip system observed in zirconium crystals deformed at 77", 575", and 1075OK was (1010) [1210] with a critical resolved shear stress in tension of 1.0 kg per sq mm at 77°K; 0.2 kg per sq mm at 575 °K; and 0.02 kg per sq mm at 1075 OK. The active twin planes were {1012}, (1121}, (11221, and (11233) with varying temperature dependence. A detailed analysis for the slip direction using Laue spot asterism is appended. NeARLY all metals of the hexagonal close-packed structure exhibit basal slip, i. e.,(0002)<1120>- type slip. This is true of magnesium,&apos; zinc,&apos; cadmium,3 beryllium,4 titanium,= yttrium,6 and rhenium.Many of these such as titanium 5&apos;8-&apos;0beryllium,4&apos;" magnesium, and zinc13&apos;14 display other slip modes even at room temperature, and nearly all have been reported to slip on other systems under particular loading or temperature conditions of testing. As is shown in this paper, basal slip was not found at any of four test temperatures from 77" to 1075°K in hexagonal close-packed zirconium under the simple loading conditions of tension and compression, even though in one case the resolved shear stress on the inactive (0002) <llgO> system was twenty-five times higher than the critical resolved shear stress on the active (1010) [1210] system. This result is consistent with prior studies on the active deformation processes in zirconium deformed at room temperature. &apos;&apos;-I7 SPECIMEN PREPARATION A) Material—The zirconium used in this work was of two types: 1) as-deposited reactor grade crystal-bar, and 2) arc-melted and forged reactor grade crystal-bar. Typical chemical and spectrographic analyses of these materials as received, and after hydrogen removal and crystal growth are given in Ref. 17. Crystals of type 1) above have the letter prefix (A) and those of type 2) have the prefix (B) throughout this paper. B) Crystal Growth— he zirconium was machined into rectangular parallelepipeds about 0.2-in. scl in cross section and 2 in. iong. These were hand polished through 4/0 abrasive paper, electropolished, given a hydrogen removal anneal, and subjected to long-time anneals at 840 °C in vacuo to produce usable crystals.&apos;7 A second technique used to obtain large crystals was to cycle the samples two or three times between 1200" and 840°C, allowing them to remain at the higher temperature for about 4 hr and at the lower temperature for 5 days.17 These techniques yielded some grains which occupied the entire cross section of the bar and were as long as 3/4 in. C) Orientation Determination—After the growth of large crystals by thermal cycling, the samples were repolished with extreme care through 4/0 abrasive paper and electropolished. Metallographic examination after polishing showed the surfaces to be free of visible deformation traces. Standard Laue back-reflection X-ray techniques were used to find the crystallographic orientations of selected large grains with respect to a specimen face and edge. Fig. 1 shows the stereographic projections of the stress axes for the crystals used. The sharpness of the spots on the Laue photographs indicated that the crystals were of good quality. EXPERIMENTAL METHODS Nine crystals were deformed in tension at 77"K, nine in tension and five in compression at 300°K in previous tests,17 fifteen in tension at 575"K, and eleven in tension at 1075°K. All specimens were stressed by load increments. After a predetermined load was applied, the specimen was removed from the loading appratus and metallographically examined for deformation traces. An attempt was made to initially stress each bar so that some crystals slipped a small amount and others not at all. This was done to bracket the critical resolved shear stress. One bar of special orientation (B-11) was repolished and annealed at 1075°K for 1 hr after lower temperature deformation, before final deformation at 1075°K. In the other bars the loading by increments, followed by metallographic examination, was continued until the surface distortion would interfere with analysis, or until fracture. One example of a crystal pulled to fracture is shown in Fig. 2. This photograph shows a crystal (B-14C) which was pulled at 1075°K and failed by slip on two (10i0) planes. The approximate orientation of this crystal is illustrated in the figure. Specimens were deformed at 77°K in liquid nitrogen on a tensile machine using an insulated bucket with an internal hook to accept a clamped specimen.

Jan 1, 1961

Molybdenum was first discovered on the Continental Divide in Colorado in 19 11; and in 1918 two companies, one of which was the Climax Molybdenum 250 stpd operation, were producing. In 1919 both mines were shut down, but in 1924 the Climax mine reopened and has been producing ever since. Over the years mine production has been increased until today the mill capacity is 48,000 stpd (43,500 mtpd). From 1935 to 1973 all ore was mined underground by block caving with scraper slushing. Since 1973 ore production has been supplemented by open pit mining. As demand for molybdenum increased, upper levels of the mine became worked-out and new lower levels were opened. In late 1972 production began on the 600 level with the mined ore being primary and secondary crushed in the new No. 4 crushing station. Ore is hauled to the primary in 10 st (9. 1 mt) capacity Granby side-dump cars. The trains, carrying 200 st (181 mt), pass throug.h a dump block and discharge directly into a 54 in. by 84 in. Traylor TC gyratory crusher set at an 8 in. (203 mm) open side setting. Since the ore has already been broken to a size which will pass the finger raises in the mining areas, there are only rare oversize boulders to block the crusher opening. Selection of the crusher was based more on its capacity than its receiving opening, as is often the case with gyratories used in open pit operations. Nominal and maximum capacities for this unit are 1250 and 1800 stph (1 135 and 1635 mtph). The ore is often wet and sticky, so a mechanical car cleaning device is utilized. Under the crusher is a 300 st (270 mt) ore pocket equipped with a 60 in. (1.52 m) wide inclined conveyor which delivers the ore to a 2,000 st (1800 mt) surge bin. Near the head pulley of this conveyor is a wood picking station whe re tramp wood and steel are put into cars for removal. Two more apron feeders remove the primary crushed ore from the surge bin, and impact belts and conveyor belts transport the ore to the crushing station for screening ahead of two 7 ft (2. 13 m) standard crushers. Secondary crushed ore is then conveyed to the surface for tertiary crushing. The entire underground crushing room containing the primary, two secondaries, screens and related equipment is serviced by a 100 st (90 mt) crane with a smaller capacity fast hook. A control room is situated so the operator can observe all the crushing operations. Rotoclone collectors remove dust from the entire operation (including the fumes from the zinc pots) and discharge it to the final product belt. The Rotoclones are vented through drifts and raises to the surface. Shop facilities, electrical gear, and lubrication equipment are located

Jan 1, 1978

By James Douglas

At this last meeting of our Institute for the year 1899, it is appropriate that we should look back at the past. To review the century&apos;s progress in the exact sciences and the resulting arts that fall within the scope of our labors is beyond my ability. But I wish to draw your attention to some phases of that progress, almost as important, which lie within the zone of sociology, touching at so many points the domain of applied technology. One of these is suggested by the library of technical literature which this century has produced —not the least important contribution to which is our own Transactions. The nineteenth century has witnessed the beneficial spread of democracy in politics. Under the impulse, to no small degree, of the same spirit, there has grown up a brotherhood of fellow-workers and a sense of fellow-ownership in the secrets of nature. Though the Patent Office has assumed such proportions as to hare become a source of national revenue, and a multitude of inventors, great and small, are seeking through its agency to secure some pecuniary profit from their devices, there is even greater eagerness among both interested and disinterested workers in the field of technology to publish their observations, and even their discoveries, and to give them to the world without remuneration. The motives influencing the great body of writers who, without any pay, use the technical journals and such media of communication as our Transactions, in order to give to the brethren of their craft the results of

Jan 1, 1900

By L. A. Weitzenkamp, N. M. Bashara

A study of the electrical conductivity of gold films less than 200 in thickness indicates a negative temperature coefficient of resistance and a thermal actiuatlon energy of less than 0.25 ev. The films consist of discrete metal islands of linear dimensions from a few angstroms to 1000A. Films were able to withstand applied fields up to 60,000 v per cm before breakdown occurred. A model for the conduction mechanism is proposed which involtes a Potential barrier due to work junction, irriage forces , and an electrostatic potential arising from separating an electron from a neutral island leaving behind a positively charged metal island. Activation energies of less than 0.25 ev ave consistent with this model, which includes a tunneling andor Thermal mechanism for conduction between the separate metal islands. An apparent satuvation effect in conductivity at high fields is observed experimentally. The saturation effect may be explained by the influence of the electrostatic contribution to the potential barriers for the transition through several islands adjacent to the original island which was activated to give up an electron. The proposed model gives Poor quantitative agyeement for the intermal electrical field between islands. ThIS paper will relate the structure of discontinuous metal films to the electrical properties and will emphasize the following topics: 1) the relation of the conduction mechanism to particle size and a comparison of particle size from electrical measurements with electron-microscope studies; 2) the saturation of the conductivity at high electric fields; and finally, 3) a comparison between the external field applied and the apparent field between particles. che- latter comparison points to a need for a modification in the model for the conduction mechanism first proposed by orter&apos; and expanded by Neugebauer and webb2 which will be dealt with in the discussion. The paper is based on results on gold films on glass microscope slides. The clms were vacuum-evaporated and were about lOOA thick, thickness being measured by interferometry. It has been observed that metal films of this thickness do not exhibit bulk metallic conduction. Films thinner than some critical thiclmess, depending upon substrate temperature and other factors, have conductivities which increase with increasing temperature with thermal activation energies of less than 0.25 ev. Electron-microscope studies3 have shown that these films consist of discrete metal islands having linear dimnsions from a few angstroms to approximately 1000A. When the metal is being vacuum-deposited on the substrate, islands on the order of a few angstroms appear first. As the deposition continues the islands may tend to agglomerate into larger particles and may eventually grow together into a continuous film,3&apos;&apos;&apos; In our tests the conductivity of the gold films was found to be about ten orders of magnitude less than the bulk conductivity of gold. When oxygen was introduced into the test chamber the conductivity decreased by a factor of about one-third. This can be related to an increase in work function for gold caused by adsorption of oxygen, as reported by Oullet and Rideal.s Exposure to an atmosphere of water vapor caused an increase in conductivity by a factor of 2 or 3 when a low field was applied. When the films were exposed to water vapor under a high field the conductivity increased by as much as two orders of magnitude. The activation energies measured were much less than the work function for gold, 0.25 ev or less, with the smaller activation energies observed for thicker films. It will be shown that the activation energy is a function of particle size and spacing. In general the model for the potential between metal islands would include the effective work function, the image force, the applied field, and an electrostatic term. The electrostatic contribution arises from the potential required to separate an electron from a conducting sphere. According to Neugebauer and webb2 the maximum potential due to the field and the electrostatic term only is

Jan 1, 1967

By Charles A. Ashburner

&apos; I. Natural-Gas Explorations. The rapid development of the natural-gas* industry in Western Pennsylvania, and the great economy which results from its use, both for manufacturing and domestic purposes, has led to an inquiry as to the occurrence of this gaseous mineral in all thickly populated and large manufacturing centers of the United States. Natural-gas springs are to be found in almost every State in the Union, and in many States gas has been obtained in wells sunk either for water, oil, or gas, or in search of solid mineral deposits. The occurrence of natural gas is, however, not dependent upon mere chance, as is popularly supposed, but upon the existence of special geological phenomena; this fact is now recognized by professional men and by many practical men concerned either in the exploration for or in the use of this gas. The desire among our leading manufacturers, to emulate Pittsburgh, has led to the sinking of many wells in many localities, in search of natural gas. Some of these wells are now being located and drilled under the direction of professional experts, but many more have been, and are still being located by "quack " explorers, who often depend upon spiritualistic communications, or the diviningrod, or by intelligent persons, who are ignorant, however, of the geological and physical conditions under which gas has already been found. My attention has recently been directed to a number of these exploring operations where holes have been drilled, and, after failing

Jan 1, 1887

By Edward Keller

In order to conduct intelligently the sampling of copper of various forms and grades, solid or in molten furnace-charges, a knowledge of this subject is essential. Yet figures and tests have been persistently withheld from publication, and the books at our command give us little or no information in this regard. This gap in our copper-literature has led to a series of experiments, the results of which are given below. Nearly all gold- and silver-bearing copper, destined for shipment, is cast into the form of bars or pigs. For the sampler, the question arises, Does copper, so cast, remain homogeneous ? If it does, sampling should present no difficulties; but, from experience, we know that this is not the case, and we are thus led to study the behavior of the precious metals arid impurities in copper when the latter changes from the molten to the solid state. For the purpose of the experiments here described, all available grades of copper were selected, and all of them mere subjected to the same conditions, an important requisite for proper comparison. The molten copper obtained directly from reverberatory- and blast-furnaces was cast in a cast-iron mould, the sides and bottom of which were 1 inch thick, and would, therefore, give the copper a fair length of time to chill. The inside dimensions of the mould, and, consequently, of the block of copper obtained, were: length, 10 inches; width, 9 inches; and depth, 5 inches. Fig. 1 illustrates the method employed to obtain samples from these blocks. A was cut away, and the face so produced BALTIMORE COPPER WORKS,

Jan 1, 1898

By L. F. Tedsen, A. E. Flanigan, J. E. Dorn

SINCE aluminum-alloy sheet may be used occasionally at moderately elevated temperatures, the effects of temperature en the mechanical properties are of interest. Recently the short-time tensile properties of several high-strength materials have been studied at temperatures up to 375°F. This paper deals with stress-rupture and [ ] creep properties at the same temperatures. The work was done at the University of California as a portion of the project NRC-548. It was financed by the War Production Board and was supervised by the Office of Production Research and Development. This paper has been released for publication by the latter agency. The following materials were studied, all in the form of 0.040-in. sheet: Alclad 24S-T Alclad 24S-T8I Alclad 24S-T86 Alclad 75S-T R301-T (clad) [ ] Specimens were loaded in tension in the cross-grain direction. Testing temperatures included 94°F., 211°F., 300°F., and 375°F. Stress levels were selected to cause rupture in times ranging from several minutes to boo hr. In each test the following data were obtained: (I) fracture time, (2) elongation at fracture, (3) the complete strain-versus-time curve (creep curve), (4) creep rate (defined in a later section). MATERIALS Materials for specimens were obtained from the manufacturers&apos; commercial

Jan 1, 1946

By R. A. Salathiel, A. D. Kaiser, P. H. Monaghan, B. E. Morgan

The productivities of many hydrocarbon-bearing for-rnntions appear to be reduced during drilling, completing and repairing operations. The reason for these othcarwise unexplainable low productivities may be a drastic reduction of formation permeability immediately surrounding the borehole. A possible cause of the reduced permeability is swelling and dispersion of clays present in porous media when contacted by fresh water or mud filtrates. Hence, the invasion of fresh water or mud filtrate into hydrocarbon-bearing formations that contain clays may cause low productivities as a result of formation damage. Present laboratory investigations have yielded results which supplement existing literature on formation damage. An expanded-type clay, montmorillonite, way found in hydrocarbon-bearing formations not previously analyzed. When sand columns and formation cores containing montmorillonite were contacted by fresh water, their oil permeabilities were reduced. This reduction in oil permeability way restored partially but not completely by a repair procedure, i.e., flooding with kerosene containing organic agents or flooding with water containing electrolytes. Hence, where montmorillonite is present in formations, prevention of formation danzage was indicated to be the only complete solution to the problem. To prevernt formation damage, results suggested use of an approximately 1 per cent solution of calcium chloride or stronger solutions of sodium or potassium chloride. In conventional rotary drilling operations the wall of the hole is exposed to drilling mud for days, weeks, and in some instances for as long as several months. During this time, drilling mud filtrate seeps slowly into formations surrounding the hole. The permeability and stability of many formations, especially those containing clayey materials, are impaired by the mud filtrate. Often interaction between the mud filtrate and the formation causes drilling and production difficulties. Serious reduction in productivity of oil and gas formations during drilling, completing and repairing wells has been noted often in recent years. Cases are known of development wells which produced only small volumes of fluid upon completion. However, after a period had elapsed, they began to produce oil or gas in commercial quantities. In other cases, results of drill-stem tests taken during the drilling of deep wells have indicated good production should be obtained from shallow formations. Later difficulty has been experienced in obtaining production from these shallow formations which had remained in contact with drilling muds for an extended time. In yet other cases wells have failed to attain the productivities expected from previous performance after the use of drilling mud as a circulating fluid during workover operations. It is evident from the field behavior cited that the productivities of certain oil- and gas-bearing formations have been damaged by exposure to drilling muds. This reduction in well productivity, called "formation damage", causes serious consequences. In development wells, expensive remedial operations are incurred. In wildcat wells, good formations may appear to be marginal or even non-productive. The importance of formation damage has been recognized by a number of investigators1-s who have considered the effects of fresh water, saline solutions and aqueous mud filtrates on the permeabilities of formations. A general conclusion from such studies is that interaction between water and formation clays reduces permeability of reservoir rock and that the permeability decreases as salinity of the water decreases. Data in these references, however, concern the permeability change with only a single fluid present. A more pertinent and direct consideration in the production of oil and gas from wells is the permeability change when two fluids, oil and water, are present. Recognizing this, Nowak and Kreuger2 and Bertness1" considered several ways in which mud filtrates and saline solutions caused reductions in the oil permeability of formation cores. Investigations discussed here were designed to supplement information in the literature on changes in oil

By Alfred H. Bell, Virginia Kline

In 1944, Illinois produced 77,413,000 bbl. of oil, or 4.6 per cent of the total for the United States, and continued to rank sixth in the nation in oil production. This represents a decrease of 6 per cent from 1943, when- the total Illinois production was 82,256,000 bbl. This decrease was much less than the 23 per cent decrease in 1943 from production of the previous year. The principal factor in arresting the production declinc, which had been going on since 1941, seems to be the increased drilling that followed the relaxing of the Federal Government&apos;s rules in regard to well spacing. The daily average production for 1944 was approximately 212,000 bbl. Daily averages by months were as follows: Jan......... 219,000 July........ 206,000 Feb......... 220,000 Aug......... 211,000 Mar........ 216,000 Sept......... 209,000 Apr......... 211,000 Oct......... 210,000 May........ 213,000 Nov........ 209,000 June........ 209,000 Dec......... 205,000 During the year, 1991 wells were drilled for oil and gas in Illinois as compared with 1791 in 1943, an increase of II per cent. Of the 1991 wells, 430 are classified as "wildcat" as compared with 461 in 1943. Twenty-eight new pools (Table 2 A) were discovered in 1944 as compared with 29 in 1943. Changes in federal drilling regulations, permitting closer spacing of wells, resulted in a drilling program that emphasized development of proved acreage rather than wildcatting. Data on production and drilling by fields are given in Table I; data on annual production and drilling for Illinois, in Table 3. Discoveries Twenty-eight new fields (Table 2 A), 42 extensions (Table 2 B), and 39 additional producing zones in existing fields (Table 2 C) were discovered in 16 counties in Illinois during 1944. Of the 28 new fields, one was abandoned during the year, 14 were one-well fields, eight others had not more than 6 wells, one had 8, one had 9, one had 11, one had 15, and the largest new field, Roaches North, had 28 producing wells at the end of the year. In all, 109 wells were producing in these new fields on Jan. 2, 1945, as compared with 111 wells producing from 29 new fields at the end of 1943. . The average initial production of the discovery wells of the 28 new fields was 129 bbl. of oil and II bbl. of water, a notable decline from the average initial production of 194 bbl, of oil and 15 bbl. of salt water for the 1943 discovery wells. In fields discovered since 1936, the total number of oil wells producing at the end of 1944 was 12,335. Productive Acreage The area of proved production in the new fields (discovered since 1936) increased from 144,335 acres at the end of 1943 to 173,485 acres at the end of 1944 (Table I), an increase of 29,150 acres. Of this increased area, 1720 acres are in fields discovered during 1944 and 27,430 acres are in extensions of fields discovered earlier.

Jan 1, 1945

By Robert E. Cuthbertson

IT is the purpose of this paper to describe in detail the laboratory development and mill application of an unusual combination of flotation reagents employed in the concentrator of the Climax Molybdenum Co., on the Continental Divide, near Leadville, Lake County, Colorado. This development originated in an ore-dressing research laboratory maintained by Climax at the experimental plant of the Colorado School of Mines, which is staffed by men directly employed by the Climax Molybdenum Co. Mill-scale testing of laboratory developments was supervised by a representative from the testing laboratory, working in close cooperation with the operating staff at the mill. General milling practice at Climax is ably described in a paper by E. J. Duggan,1 mill superintendent. Other aspects of the Climax project have been described in papers by W. J. Coulter,2 by Butler, Vanderwilt and Henderson3 by Allen Kissock,4 and by Leo H. Glanville.5 Consequently, this paper will be confined to the metallurgical aspects of recent reagent developments, avoiding, as much as possible, repetition of material covered in these earlier publications. BRIEF HISTORY OF REAGENT PRACTICE AT CLIMAX Prior to the year 1937, the only reagents employed at Climax for froth production and collecting action in the flotation of molybdenite were steam-distilled or destructively distilled pine oils. The only exceptions to this practice were brief periods of mill testing, when reagents of various types were tried on an experimental basis. None of these experimental runs was sufficiently encouraging to justify its continuation as regular practice. Sodium, cyanide has been employed since the very early days of milling at Climax as an inhibiting agent for control of pyrite and chalcopyrite. Alkaline reagents such as lime or soda ash have been used in recent years to minimize the detrimental effect of iron salts on flotation of molybdenite. The presence of these harmful salts is attributed to the decomposition of fine metallics abraded from liners and balls in the first stage of regrinding rougher concentrate. Flint pebbles are used in subsequent regrinding, since alkaline reagents are not entirely adequate to offset the inhibiting effect of iron salts as the grind becomes progressively finer and the grade of concentrate progressively higher. Climax metallurgists were familiar at an early date with the use of petroleum products such as kerosene and gas oil as promoters of flotation of molybdenite. Charles C. Oliver6 discussed the use of pine oil and kerosene as early as 1920, in connection with the milling practice at Dominion Molybdenite Co., Quebec. Never theless, the early attempts to apply this knowledge in the Climax concentrator were complete failures. In the light of recent experience, it may seem strange that the early mill tests with petroleum

Jan 1, 1944

By Walter P. Jenny

I. The Reducing Action of Carbon and of Hydrocarbons,. .. 445 11. Protective Action of Carbon and of Hydrocarbons,. 451 111. Contributory Action of Carbonic Acid Gas,..452 IV. The Stability of Carbonic Acid and of Water,..453 V. Occurrence of Carbon and the Carbon-Compounds,. 455 VI. The Occurrence of Carbon, Alone,.... VII. The Occurrence of Carbon Combined with Hydrogen,. .. 460 VIII. The Relative Reducing Power of Minerals,..487 I. The Reducing Action of Carbon and of Hydrocarbons. Carbon has long been recognized as one of the most powerful reducing agents in the deposition of ores. Investigations, made by myself, of the zinc- and lead-deposits in Southwest Missouri, in the region centering about Joplin, where the formation of the metallic sulphides has been due to the action of bitumen, carbonaceous shales and bituminous coal, have afforded abundant evidence that the solid oxygenated hydrocarbons, particularly when in fine powder and in suspension in the waters circulating through the ore-bodies, are the most energetic and powerful reducing agents known. Bitumen, liberated by the decomposition of the ore-bearing limestone, is found in the Joplin mines in all degrees of fluidity and hardness, dependent on the amount of oxidation it has undergone. From semi-fluid maltha it grades into partly oxidized mineral-pitch, which, by further oxidation, changes to hard asphalt, finally breaking up, from continued absorption of oxygen, into a fine powder resembling in appearance powdered coal. In this condition oxidized bitumen, from its light gravity, is transported readily in suspension in the underground circulating-waters. Bituminous coal and black carbonaceous clays and shales occur as surface formations, often in intimate association with

Jan 1, 1903