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By John Sasadi

The mining industry depends upon inexpensive water transportation. Today, large quantities of mined products are transported by ships over oceans, from continents to continents, over lakes and waterways to the ultimate users. Sometimes, the routes these Bulk Carriers travel cover only a few hundred miles, sometimes thousands of miles halfway around the world. Most of the products of the mining industries are relatively inexpensive. A significant portion of their cost to the ultimate users are in the cost of transportation and not in loading and unloading these commodities at the ports of origination or destination. So far, the industry has produced very efficient loading and un- loading installations, but has very little influence over marine transportation or the design of the vessels themselves. Very little was ever published dealing with integrated transportation systems properly correlating all phases of the operation; namely, loading, marine transportation and unloading bulk materials.

Jan 1, 1967

By M Zhu, G Tranell, J You, K Tang, X Ma

The thermal conductivity of slag is critical for the efficiency of high temperature metallurgical processes such as the smelting reduction of ferroalloys, the ladle refining and the continuous casting mold flux in steelmaking. Experimental determination of slag’s thermal conductivity is fraught with challenges, as seen in yielding data for the SiO2-Al2O3-CaO system that are often inconsistent and widely dispersed. In molten slags of this system, thermal transport occurs via phonons within the network structure. To quantitatively describe thermal conductivity based on the microstructure, hightemperature Raman spectroscopy was employed to measure the silicate tetrahedra Qi (i = 0, 1, 2, 3), with Q4 species inferred from mass balance. This study also integrated molecular dynamics simulations to provide a fundamental understanding of the microstructure units distributions. Machine learning algorithms, especially deep neural networks, were applied to establish the relationship between slag composition and the configuration of tetrahedra. The thermal conductivities were then connected with silicate tetrahedra Qi using an Arrhenius-type formalism. This study sets the stage for extending our findings to more complex, multicomponent slags, enhancing their practical application in industrial processes.

Aug 21, 2024

By J. J. McClellenand, R. A. Jankowski

Face ventilation and water sprays are the primary controls used on continuous miner sections to protect workers from respirable coal and silica (quartz) dust. Laboratory tests were conducted by the U.S. Bureau of Mines to determine the impact on respirable dust concentrations when increasing airflow from 3000 to 9000 cfm (1.42 to 4.25 m3/sec), water flow from 15 to 35 gpm (0.057 to 0.132 m3/min) , and water pressure from 80 to 200 psi (5.52 x105 to 1.38 x106 pa). The effective limits for each control and interactions between these controls were of particular interest. Initial analysis concentrated on defining the impact of the control parameters on the respirable fraction of the feed dust, which was a blend containing 90% coal and 10% quartz. Gravimetric sampling indicated that airflow had the most significant individual impact on respirable dust levels and resulted in reductions of 99% at the operator and 57% in the return. Regression modeling was used to predict dust concentrations at the operator and in the return. Significant interactions were observed between control parameters and often, defined the level for a control parameter where increases above that level did not significantly benefit dust control. Increasing airflow to 8400 cfm (3.96 m3/sec), water flow to 25 gpm (0.095 m3/min), and water pressure to 140 psi (9.65 x105 Pa) typically provided respirable dust reductions at both sampling locations, while optimizing use of control resources. After determining these relationships for the total respirable fraction, selected filters were analyzed for quartz content to define the impact on the quartz component of the feed dust. For the individual control parameters, airflow again had the most significant impact and resulted in reductions of 98% at the operator and 26% in the return. Regression modeling of the quartz concentrations indicated that no significant interactions between control parameters were present. At the operators location, airflow was the only parameter identified as having a statistically significant reduction for quartz dust. A reduction in quartz approaching 95% was observed for increasing airflow to 6000 cfm (2.83 m3/sec). Increases above 6000 cfm had little additional impact. In the return, a linear relationship between control parameters and quartz levels was observed with reductions of approximately 27% predicted for increasing any one control parameter to its maximum level. The synergistic impact of increasing all control parameters to maximum levels resulted in a maximum predicted reduction of 81%.

Jan 1, 1991

By W. Petruk

Mineralogical studies and concentration tests were conducted on samples from an oolitic iron deposit from the Peace River district in Alberta to determine what concentrate grades and metal recoveries could be obtained. The samples assayed 32 to 37 wt. % Fe, and consisted of goethite, nontronite, ferruginous opal, siderite , quartz, amorphous phosphate and illite . Flotation with fatty acids yielded the best over-all results. A flotation concentrate from a composite sample of the iron horizon assayed, by weight, 43.0% Fe, 12.3% SiO2 , 1.9% CaD, 0.9% MgO, 4.5% Al2O3 and 2.0% P2O5 and lost 17.2% on ignition, for an iron recovery of 48.8% and a silica rejection of 80%. When heated to drive off the water, the concentrate assayed 52 w t. % Fe and 14. 8% w t. % SiO2

Jan 1, 1977

This report, the second in an annual series, summarizes information on latest technological developments and advances, and identifies trends in mining and metallurgy based on a review of activities in the minerals industry in 1971. Exploration and mining data obtained from an annual canvass are presented for 1971 and are compared with similar data obtained over the past decade.

Jan 1, 1973

By J Zhang, R Dimitrakopoulos

A two-stage stochastic mixed integer non-linear program is formulated for a mining complex to optimise strategic and tactical plans. The objective is to find the near optimal decisions for a mineral supply chain in the context with uncertainties in both ore supply and the commodity market (price and demand). The endogenous spot price in the commodity market and long-term sales contracts are considered in the formulation of the mining complex’s optimisation model and an ad hoc heuristic is developed to deal with the throughput – and head-grade-dependent recovery rate in processing plants. Numerical results indicate that the proposed heuristic is effective and efficient in numerical tests. Based on the proposed model and heuristic, a long-term contract design strategy is proposed for making decisions on the contract price and strategic investments. A shadow price based method is also proposed to evaluate the existing mining schedule.CITATION:Zhang, J and Dimitrakopoulos, R, 2014. Optimising a mineral supply chain under uncertainty with long-term sales contracts, in Proceedings Orebody Modelling and Strategic Mine Planning Symposium 2014 , pp 25–32 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 24, 2014

By Michael Rieber

The increase in f.o.b. mine prices of coal from $5/ton to over $18/ton in five years [1] has increased the significance of transportation costs. Coals produced in the vicinity of the consumer bear a much lower transport cost than those produced in the west. This differential may be used for flue gas desulfurization, other cleaning, or further processing of local coals. To the extent that western coals are cheaper to produce and have a lower sulfur content, they offset the locational disadvantage. To the extent that they have a lower heating value, the disadvantage is exercabated. Given the other conditions, an accurate analysis of transport costs will help suggest the location of coal mining and the moue of transport both transport costs and tariffs have risen. Together they have increased delivered coal prices, altered the balance between the use of coal and other fuels, helped to alter the location of mining activity, and put pressure on consumers to examine the cost effectiveness of alternative transport modes. Transportation options for long distance coal movements include rail, barge, pipeline, and EHV transmission lines. A summary of system parameters is shown in Table 2.1. Barge transport, pneumatic and slurry pipelines are discussed elsewhere in this report. Together with EHV, they have been the subject of previous studies [2,3,4]. Slurry pipelines have been shown to be especially useful where rails are not available [2] but the technical problems of dewatering, handling, and utilization of lines [5] remain unresolved. They are discussed in Section 3. Barge transportation depends on the location of the mine and consumer with respect to the waterway system. One drawback of barge shipment is interruptions due to winter, and low or high water conditions. Mine mouth power generation followed by EHV transmission of over 500 miles has been shown to be the most expensive means of delivering an equivalent amount of energy to consumers [2].

Jan 1, 1977

By W. E. C. Eustis

In September last I had my attention called by Mr. R. G. Leckie to a deposit of nickel in the township of Orford, province of Quebec. In many ways it has proved to be a subject of great interest. As this ore is, as far as I can learn, entirely new in mineralogy and metallurgy, it has seemed to me that it would be a matter of interest to the Institute to have laid before it, in a short paper, the peculiarities I have met with in studying it. This deposit of nickel was first described by Dr. T. Sterry Hunt, our President, in the Geology of Canada, 1863, p. 738, in the follow ing terms: " The general diffusion of nickel throughout the magnesian rocks of the Quebec group has been already noticed. It has, however, never been met with in any considerable quantities in these rocks, although workable deposits of its ores may reasonably be looked for

Jan 1, 1879

Abbey, Robert Graham, District Mgr. The W W. Sly Mfg. Co,. 50 Church St, New York, N. Y. '21 Abbott, A. N., Mines Supt., Mazapil Copper Co., Ltd ..Concepcion del Oro, Zac., Mexico. '23 Abbott, Argyle Campbell, Dev. Dept, E I du Pont de Nemours & Co, Wilmington, Del. '29 Abbott, Clarence E., V.P, Charge of Raw Materials, Tenn. Coal, Iron & R. R. Co, 1242 Brown-Marx Bldg, Birmingham, Ala. '04 Abbott, Louis Benjamin, Chief Engr., Elkhorn Div., Consolidation Coal Co, Jenkins, Ky. '15 Abeel, George H., Jr., Cons. Min. Engr Box 427, Santa Monica, Cal. '18 Abel, Albert E., Asst. to Pres, Valley Mould & Iron Corp Hubbard, Ohio. '19 Abel, Raymond L., Asst. Prof., Dept. of Pet Refin., Univ. of Pittsburgh Pittsburgh, Pa. '28 Abell, Leo M., Research Engr, Sullivan Concentrator Chapman Camp, B. C., Canada. '31 Abernathy, George Elmer, Prof. of Geol. & Min . Kansas State Teachers College, Pittsburg, Kans. '20 Aborn, Robert H., Research Lab, U. S. Steel Corp. Lincoln Highway, Kearny, N. J. '19 Abozeid, Mahmood, Dept. of Mines & Quarries Cairo, Egypt. '26 Abraham, Arthur W. Box 1466, Bakersfield, Cal. '20

Jan 1, 1923

By C. H. B. Leitch

"The Bralorne-Pioneer deposit produced more gold than any other deposit in British Columbia over its 70 years of operation (130 kg or 4 million oz of Au, from 7 million tonnes of 18 glt ore). Mineralization is related to a suite of late Cretaceous albitite dykes of 85 to 90 Ma age. It thus occurred long after and is genetically unrelated to the Early Permian (275 Ma) Bralorne diorite and soda granite.The major veins strike about 110 degrees and dip north at 70 degrees, with slickensides plunging 45 degrees east that indicate last movement was reverse. Major ore shoots in the veins occupy somewhat less than 20% of the vein and plunge steeply west, roughly perpendicular to the slickensides. The structures that contain the veins probably formed at around 95 to 90 Ma during a strike-slip episode with easterly directed maximum compression.Disseminated pyrite, pyrrhotite, and minor chalcopyrite occur within envelopes up to several metres from the veins. Arsenopyrite is confined to vein selvages. Local sphalerite and galena appear to correlate with gold-rich portions of the veins. Traces of tetrahedrite and stibnite have been observed but tellurides have not. Gold is found principally as thin smeared flakes of the native metal in the black sulphidic septae of the strongly ribboned veins. Hydrothermal alteration envelopes around the veins grade outwards from intensely foliated quartz - ankerite - sercite (±fuchsite) to less sheared calcite - chlorite - albite to unsheared epidote -calcite.Open-space vein filling textures found in the deep (mesothermal) environment at Bralorne can be explained by a fault- valve model. High-angle reverse faults may have acted as fluid-pressure activated valves on geopressured reservoirs, causing large cyclic fluctuations in fluid pressure that promoted mineral deposition in an episodic fashion . The faults that were mineralized were reactivated sub-vertical former strike slip faults, oriented at a high angle to the northeast-directed stress in a compressive regime."

Jan 1, 1990

By Charles R. Marek

There is an ever-increasing need for quality construction materials to provide the necessary housing and transportation facilities required for the protection and movement of people and goods. By the year 2000, requirements for housing in the United States will have doubled due to population growth. Requirements for transportation facilities in this same period will also have increased substantially. Further, all existing facilities for both housing and transportation will require substantial maintenance of one form or another. Aggregate is the basic material of the construction industry. There is some occurrence of aggregate source material in virtually every state of the United States, and in every country in the world. United States reserves of commercially useable aggregate have never been systematically estimated and are probably so vast as to be incalculable.1 However, in many areas its existence is largely negated by inaccessibility. Often it is lodged deeply or intricately in the earth or it is too distant from markets to offer a desirable "return on investment" under the present economic structure. Other factors that prevent its utility are the occurrence of small scattered deposits that individually are too small to justify the necessary capital investment for exploitation and collectively are too widely disseminated; also, the aggregate nay be deficient in certain desired chemical or physical qualitites.1

Jan 1, 1974

By Jaeheon Lee, Junmo Ahn, Isabel F. Barton

"Newmont’s Mike prospect, currently undeveloped, is a blind Cu-Au(-Zn) deposit on the Carlin Trend, containing >8.5 M oz. Au, 1027 M lbs. Cu, and 809 M lbs. Zn as Carlin-type gold and polymetallic Cu-Zn minerals in Paleozoic lower-plate carbonates and shales. This project was undertaken 1) to examine the effectiveness of different lixiviants for leaching the Mike supergene Cu-Au ores via bottle roll tests, and 2) to determine what ore minerals resist dissolution in each leaching agent by comparing the mineralogy and chemistry of head and tail samples. Sulfuric and sulfurous acids were used to leach copper and cyanide was used to leach gold. Thiourea, glycine, and other lixiviants were used to leach both base metals and precious metal. QEMSCAN and SEM study of six samples of different ore types and grades indicate that the Au occurs as varieties of native gold, including auricupride and electrum. Major Cu minerals are native Cu, cuprite, malachite, chrysocolla, and conichalcite (Ca-Cu arsenate), with locally significant Cu in jarosite and goethite. Gangue mineralogy is dominated by quartz, sericite, chlorite, alunite, smectite and kaolinite, K-feldspar, and iron oxides (sensu lato). Results of bottle roll tests and leach residue mineralogy will be presented and discussed at the conference.INTRODUCTION Resource and Geologic Setting The Mike deposit is a large, blind Cu-Au(-Zn) deposit in the Maggie Creek district of the Carlin Trend of Nevada, USA, near the Gold Quarry mine (Figure 1). The mineral inventory, based on drilling, is 8.568 Moz. Au, 1027 M lbs. Cu, and 809 M lbs. Zn at average grades of 0.72 g/t Au, 0.34 wt% Cu, and 2.13 wt% Zn (inventory for a cone at $400/oz Au and $0.80/lb Cu by Norby and Orobona, 2002)."

Jan 1, 2017

By R. R. Sayers

A series of coal- mine catastrophes in the latter part of the first decade of this century focused public attention on the need for safety in mines and resulted in the establishment of the Federal Bureau of Mines , whose primary function was to promote safety and improve hygienic conditions of workers in the mineral and related industries . These activities are carried out by the Safety Division of the Bureau's Health and Safety Service . In general , the work performed by the Safety Division personnel may be classified as educational and investigative . Instruction is given in accident prevention for mine officials and miners ; first aid to the injured ; the use and care of oxygen breathing apparatus ; and advanced mine rescue and recovery operations . A specialized safety course is offered to the petroleum and gas industries . Division personnel also aids in or directs rescue and recovery work after mine fires and explosions ; assists at first - aid and mine rescue contests ; conducts safety exhibits and demonstrations ; and presents safety talks , often accompanied by sound safety motion pictures or latern slides , before employee and official groups , at meetings of Holmes safety chapters , at mining institutes , and at other safety or technical gatherings . Coal - mine fires and explosions are investigated , as well as quarry or metalmine explosions and fires , miscellaneous accidents , health and safety hazards , and safety conditions at mines and plants ; safety devices are investigated and developed . Field studies cover ventilation , methods of allaying suspended coal - dust particles , prevention of dust accumulations , the proper use of rock dust to prevent or limit explosions , explosives practices , and the care and use of underground equipment . The results of these studies and investigations are widely applied in the various training courses and are prepared as reports and recommendations , which are submitted to interested persons or are combined and distributed to the public as bulletins , technical papers , miners ' circulars , information circulars , and reports of investigations . These studies also afford a basis for the development of new or modification of old Safety Decisions of the Mine Safety Board of the Bureau of Mines . The following pages review the accomplishments of the division as regards safety during 1942,2/ with like information for a series of recent years and summaries to date . A striking feature of the division's work has been the safety education of more than 1-1/2 million persons who have taken first -aid and mine rescue training courses . That these efforts over a period of 3 decades have been successful is revealed by the decline in coal - mine fatality rates and a somewhat smaller decrease in metal - mining and quarrying fatality rates .

Apr 1, 1943

By S McKnight, L Koroznikova, S Hall

Mineral sands represent an important new resource being developed in the Murray Basin, including parts of western Victoria. This paper will outline a simple methodology for mineral sands characterisation, developed as part of the AMIRA-managed project P777 æThe Development of Heavy Suspension Techniques for High Density Separations (Replacement of ClericiÆs Solution)Æ. This project is currently sponsored by three multinational mining companies (De Beers Consolidated Mines, Iluka Resources Limited and Rio Tinto Limited) and is developing an innovative laboratory mineral characterisation procedure that will allow the replacement of the currently employed highly-toxic chemicals.Mineral sand resources almost always contain more than one valuable (and relatively heavy) mineral. Titanium minerals are found with a large range of titanium contents, giving rise to density variation and often subjective mineralogical descriptions. Companies tend to rely on laboratory heavy liquid separation in the evaluation of samples arising from exploration, mining or metallurgical processes. Unfortunately, there are only a limited number of high density (æheavyÆ) liquids and these tend to be more toxic as their density increases. Low-toxicity inorganic solutions, based on tungsten compounds, have been developed that can be utilised at relative densities (RD) up to 3.0. However, beyond this value currently only organic liquids can be used. Diiodomethane (methylene iodide) having a relative density of 3.31 is commonly used; however, this presents significant health and safety hazards. Mixtures of thallium formate and thallium malonate were found in the early 1900s by Clerici to provide liquids having specific gravities between 4.0 and 5.0, hence æClericiÆs solutionÆ. For the characterisation of the heavy components of mineral sand deposits (eg anatase sg 3.9, rutile sg 4.2, ilmenite sg 4.4 û 4.7 and zircon sg 4.6 û 4.8) there is currently no heavy liquid alternative to ClericiÆs solution. ClericiÆs solution is highly toxic and testing is now conducted by very few laboratories worldwide with costs reflecting the chemical costs (though extensive efforts are made to recover and reuse the liquid, plus the requirement of its removal from the mineral samples), the infrastructure costs and health and safety regimes (eg blood testing of exposed staff, inventory management). A simple laboratory technique of density fractionation is being developed, employing suspensions of fine tungsten carbide particles in lithium heteropolytungstate (LST) solutions, that can replace ClericiÆs solution in the evaluation of fine mineral sands samples (eg -250+150 microns). The developing methodology that can achieve low-cost, low-toxic separations at relative densities above 5.0 will be outlined and the comparison of results with ClericiÆs solution presented.

Jan 1, 2006

By John J. McKetta. Jr., Louis B. Lesem, George H. Fancher

The proration of oil produced in the field frequently is based partially or entirely upon the gas-oil ratio of wells. The measurement of the gas-oil ratio is one of the more important field tests in regulatory and pro-ration work, and the test always should be conducted according to standardized methods and procedure. Obviously, the gas-oil ratio and the volume of gas produced by a well depend upon many factors but should be independent of the method of measurement and of the devices used to measure gas and oil. Consequently, the volume of gas accompanying a barrel of oil produced by a well may be measured by any reliable and accurate device or instrument. Frequently either a critical flow prover or an orifice well tester is used for this purpose, and for a particular well the same rate of flow of gas should be obtained regardless of whether a critical flow prover or an orifice well tester is employed in the test. In Texas, when using either instrument, either Capacity Table 1 or 5' is employed in making the necessary computations. If the tables are used, a discrepancy always is found whenever the two instruments are compared by extrapolation to the same conditions of flow. Clearly, Tables 1 and 5 must be at fault in some respects. The orifice well tester and the Bureau of Mines type of critical flow prover are essentially the same instrument; both devices utilize a square-edged orifice 1/8 in. in di-ameter as the primary element, and both freely discharge gas to the atmosphere. Tables for the orifice well tester' have been published in the ranges of 0 to 15 in, of water and 0 to 40 in. of mercury (Hg) differential in pressure. Coefficients for the critical flow prover have been published for differentials in pressure greater than 75 psia. An extrapolation of either differs from the other set of data as much as 18 per cent at some points. No immediately obvious reasons for the discrepancy was found, and data available from the literature were insufficient to effect reconciliation. Consequently, a series of experiments was performed to check the available data and to determine discharge coefficients for the two devices in an overlapping range of differential pressure. The correlating equation used in preparation of tables such as Tables 1 and 5' is the so-called hydraulic equation, Q = C1 vh .....(1) The tables cover orifice sizes from 1/8 through 1 1/4 in. A second set of tables, for use with greater differentials in pressure, apply only to the 3/4, 1, and 1 1/4-in. orifice plates over a pressure range of 0 to 40 in. of Hg. The correlating equation used in preparation of the tables is Q = C2 vH(29.32 + 0.3H)/G . (2) Each of these equations is valid only for the range to which it has been applied, and neither equation is valid for extrapolation. Theoretical equations for flow through an orifice are based upon assumptions of fractionless flow and an emergent jet the size of the orifice. A multiplier, C,, called the discharge coefficient, is inserted into the theoretical expression to compensate for both frictional losses and the contraction of the jet experienced in the plane of the orifice. Buckingham3 shows that C, should vary with the ratio of upstream to downstream pressure for flow of a compressible fluid at any average linear velocity through the orifice less than the velocity of sound. Work published by the National Advisory Committee for Aeronautics4 indicates that the variation continues into the so-called critical flow region until the vena contracta coincides with the plane of the orifice. The NACA work, however, does not indicate a leveling off of the coefficient. The work of the Bureau of Mines5 for the critical flow prover was based on differential pressures greater than 75 psi and indicates that the discharge coefficient, Cd, is constant in this region at a value of about 0.86.

Jan 1, 1958

By V. A. Chanturiya

In Pt- and Au-keeping complex ores processing, about 10% ~ 15% of noble metals are lost with true tailings that are due to low floatability of Pt- and Au-keeping minerals by the conventional collectors. With the aim to achieve the effective recovery of noble metals at flotation of Pt-Cu-Ni and Au-keeping ores organic complex reagents keeping electron-donating atoms of nitrogen, oxygen, sulfur or phosphorus may be offered as selective collectors for the indicated minerals. These rea-gents tend to form complex compounds with PGM. Besides this, Cu-Ni-Pt and complex Pt and Au carbonated mica ores are characterized by finely disseminated (up to nanometer size) mineral forms of Pt in multivalent states. In this connection, the use of a combination of the strong ionic collectors with nonionic reactants that are capable to derivate complex compounds with multivalent PGM seems to be expedient for this type of ores. In the research new complex reactants were tested such as cyclic alkylene-trithiocarbonates, oxyalkyl butylxanthogen acid ethers, a combination of the collectors ? mercaptobenzothiazole (MBT) and dialkyldithiophosphates (DTP). Sorption and flotation tests were made with monomine-ralic samples of chalcopyrite, pentlandite, pyrrhotite, pyrite, and Pt-Cu-Ni sulfide ore samples. Sorption properties were examined by the extractive UV spectrophotometric method and potentiometric measurements. To indicate a structure of modified xanthate solutions the method of a thin-layer chromatography (TLC) was applied. The chromatographic behavior of the basic components of modified xanthate solution ? ButX, cyclic propylene-trithiocarbonate (PTTC), diethyl-dithiocarbamate (DEDC) and the product of its modification ? oxypropyl-S-ether of dithiocarbamatic acid was studied on plates ?Silufol UV ? 254?. The composition of organic solvents and its ratio in a mobile phase was deter-mined for simultaneous chromatography of the main components of a reaction mixture. It was found that operating selectivity of MBT, DTP and cyclic alkylene-trithiocarbonates incorporated in modified xanthate in relation to Pt-Cu-Ni and Au-containing sulfide minerals might be explained by an electoral sorption of this nonionic collector on a surface of the minerals studied. It was demonstrated that the application new reagent modes with the use of a combination of designed complex reactants helped to increase the extraction index of Pt- and Au-keeping minerals from complicated ores.

Jan 1, 2014

By G. T. G. Emere

The Johannesburg Branch of The South African Institute of Mining and Metallurgy was officially inaugurated at a General Meeting held in Kelvin House on Monday, 18th January, 1988. In addition to nominating committee members, Mr G. T.G. Emere delivered a presentation on the Barbrook gold-mining project, which is currently in the development phase some 40 km east of Barberton.

Jan 1, 1988

By W. R. Ingalls

THE following chronology presents the history of lead-mining in the United States in a brief form and is a useful reference in connection with the statistics of production 1621. Lead was mined and smelted near Falling Creek, Va., to supply the local demand for bullets and shot. This was the first mining and smelting of lead in what is now the United States. 1632. In a report made on the minerals of New England, lead-ore is mentioned. (Bishop, I., 470.) 1650. Supposed beginning of mining by Jesuits in Pima county, Ariz. 1651. Grant of lead-mine at Middletown, Conn., to Gov. John Winthrop.

Jan 9, 1907

By Harold M. Smith

Among the more important raw materials now utilized for the commercial production of synthetic organic chemicals is natural 'gas. Natural gas has been used as a fuel and source of energy almost from its discovery, but its potentialities as a chemical raw material were not realized until recently. Research in the use of natural gas for Chemical synthesis received great impetus from the discovery by Brooks and Humphrey4/ in 1918 of alcohols in the diluted ?acid oil? obtained by sulfuric acid treatment of cracked petroleum distillates. Experimental data soon showed that hydrocarbons from natural gas could be converted to these same products. Laboratory methods for chlorination of natural-gas hydrocarbons, particularly of methane for the production of methyl chloride, methylene chloride, carbon tetrachloride, and chleroform were known before that time but were not developed commercially. Methods for obtaining alcohol by oxidation of hydrocarbons derived from natural gas also were known before 1918 but had not received commercial consideration. Since 1918, and particularly during the past 15 years, the work of chemists and chemical manufacturers throughout the world has resulted in an accumulation of data regarding the reactivity of natural-gas hydrocarbons, and related hydrocarbons found in refinery gases or made synthetically. These data have been used to develop methods for converting hydrocarbons into chemical products and thus form the basis for a large and growing industry.

Jan 1, 1947

By M. K. Yen, W. R. Hibbard

Previous studies of plastic deformation of metals have emphasized the important role of bending and constraints during strain under relatively pure stresses.1"5 Some new phenomena such as early conjugate slip6 and polygonization7 are intimately concerned with the relief of bending stresses, the former by slip and the latter by a process analogous to re-crystallization. However, few analyses of the bending deformation of single crystals were found in the literature, and those8,9 are sufficiently previous to the modern interpretations of slip to invite further investigation in this area. The transverse bending mode of testing, using the two-point loading method, was selected because the center portion of the specimen may be considered as under a theoretically pure bending stress with a uniform bending moment. Considerable attention was given to both the lattice distortion and flow characteristics of the crystals during deformation. Experimental Proeedare A specimen under the action of equal and opposite couples at both ends is said to undergo pure bending. The shear and moment diagrams of a specimen under the two-point loading method of transverse bending are shown in Fig 1. The moment over the middle-third of the span is equal to PL/6, and the vertical shear is zero. Fig 2 (A) illustrates the stress distribution in the elastic range on a plane across the middle of the specimen. It can be seen that the normal stress has a maximum value at the extreme surfaces on the tension and compression sides, and decreases proportionately to zero as it approaches the neutral plane. However, when the plastic range is reached, the stress distribution is no longer a straight line relation, but changes in a manner which can be best illustrated as shown in Fig 2(B). The following calculation and stress analysis are mainly in accordance with the works reported by Timoshenkol0 and Kochendörfer.9 From the simple beam formula, the maximum normal stress will occur at the surface of the specimen. For a round specimen with a radius r and for a rectangular specimen with a height 2h and width 2b, the maximum normal stress, Sp, will be given by the following formulas: For round specimen: 2PL Sp = 3pr3 [1] For rectangular specimen: Sn = 8bh2 [2] Since it is reasonable to consider that slip takes place under the same conditions as in uniaxial loading, the resolved shear stress S?, along the operative slip direction will be as follows: For round specimen: 2PL sin x cos ? Sp = 3pr3 sin x cos ? [3] For rectangular specimen: PL S8 = 8bh2 sin x cos ? [4] where X is the angle between the specimen axis and the slip direction and X, the angle between the specimen axis and the major axis of the glide ellipse. It was also reported by Kochenclorfer9 that the critical bending moment, that is, the bending moment exerted on the specimen to initiate slip, should be higher than the value given by the equations stated above. Based

Jan 1, 1950