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By Ting Luo, Hongmin Zhu, Kai Huang, Shuanglong Du, Tao Gui, Yifan Xiu

"Poplar cotton, a cellulosic material, was found to adsorb metals ions effectively. In the present study, the biosorption characteristics of Pb(II) onto poplar cotton, were evaluated as a function of pH, contact time, biomass dosage, initial concentration and temperature. Within the pH range investigated (1.0-6.0), the optimal pH value suitable for the uptake of Pb(II) was determined. The maximum adsorption capacity obtained from the Langmuir model is around 0.52mol kg for the poplar cotton sorbent. Equilibration is achieved in 60min for the studied concentrations. Results suggest that the poplar cotton can be directly used as an effective and low-cost biosorbent for removal of Pb(II) from aqueous solution.IntroductionHigh value utilization of various biowastes produced in agricultural, forestry, fishing industries, etc. have attracted great interest from many researchers [1], Biomass, due to its easy availability, great abundance, low cost, easy processing, eco-friendliness and biodegradability, has exhibited exciting potential for being used as raw materials for the preparation of many new hi-tech functional products [2]. For example, using biowastes to synthesize sorbents for application in the removal of toxic substances such as dyes [3], heavy metals from the waste water [4] or in the recovery of valuable metals [5] from the ore tailings and secondary metals resources has made great progress in last decade. In present study, poplar cotton, a kind of white light fluff of poplar trees, like that of dandelion, usually flying in the air each spring was tested as a biosorbent for the remove lead ions from the water. It may also provide some good ideas for new sorbent design. Lead, as one of the typical poisonous heavy metals, for its typical toxicity and extensive pollution, was chosen to test the adsorption behavior of poplar cotton in aqueous solutions."

Jan 1, 2012

By D. A. Barr

The Galore Creek copper deposits lie in the Stikine River district of northwest British Columbia, a largely undeveloped region which possesses rugged mountain terrain with deeply incised valleys which support dense undergrowth. Timberline is normally at about 1300 m (4265 ft) and the higher levels contain glacial systems and large ice fields with peaks rising to 3500 m (I 1,483 ft). A location map of the Galore Creek area is given in Fig. 1. In the late 1920s, field parties under the direction of F.A. Kerr (1948) of the Geological Survey of Canada completed geological surveys of the district. Primary access for this work was provided by riverboats on the Stikine and Iskut Rivers. Kerr's party had to contend with extremely difficult travel conditions that required considerable backpacking, augmented by pack dogs in certain cases. Absence of ground control led Kerr to establish his own topographic maps. Among the geological data established was the recognition [ ] that small bodies of orthoclase porphyry in the district are often well mineralized with base metal sulfides. Copper mineralization in the upper Galore Creek valley, a tributary of Scud River which flows into the Stikine River some 80 km (50 miles) south of the small settlement of Telegraph Creek, was originally discovered during aerial reconnaissance by M. Morrison and W. Buckholz while prospecting for Hudson Bay Exploration and Development Co. Ltd. in 1955. Malachite- and azurite-stained out- crops in several parts of the Galore Creek watershed are clearly visible from distances of 500 m ( 1640 ft) or more. Claims were staked in 1956 and the copper showings were partly mapped, trenched, and investigated by shallow diamond drilling. Because of the remoteness of the area and higher priorities for expenditures elsewhere, no further work was undertaken and most of the claims were allowed to expire.

Jan 1, 1991

By A. E. Boudreau

It has long been recognized that platinum-group-element (PGE) deposits in layered intrusions preferentially occur in intrusions that crystallized from high-Mg parent magmas. Recent studies suggest that evaluation of any given intrusion for economic PGE potential should also include assessment of the PGE, sulfur and chlorine concentrations in the cumulates and potential parent liquids. PGE: Magmas that contain relatively abundant Pt and Pd are the best candidates for forming economic deposits. Although analyses of coeval sills and dikes are the best indicators of primary magmatic PGE concentrations, analysis of the cumulates themselves is also valuable. For example, within the Stillwater complex, background PGE values in cumulates from the ultramafic sections of the complex contain, on average, several 10s of ppb Pt and Pd. Background concentrations of this order are suggestive that the magma was not depleted in the PGE. Sulfur: Conventional petrogenetic models for the formation of PGE deposits in layered intrusions require the PGE to have been concentrated during a magmatic sulfide-saturation event. In contrast, some hydro thermal models suggest that sulfur and the PGE were mobilized from footwall cumulates by upward-migrating, high-temperature hydrothermal fluids. Both models suggest that significant PGE deposits are likely to occur at and below the level where stratigraphic increases in whole rock sulfur concentrations occur. Chlorine: In both the Stillwater and Bushveld complexes the cumulate sequences below the major PGE-bearing zones contain anomalous Cl-rich apatite. The chlorapatite component of apatite in these rocks may exceed 40% and, in the Stillwater complex, typically exceeds 90%. It is stressed that pristine igneous mineral analysis and not whole rock data be used, as whole rock Cl concentrations may be affected by very localized (grain boundary), low-temperature alteration. Intrusions that crystallized from high-Mg, high-Cl magmas appear to have the best potential to host significant PGE deposits.

Jan 1, 1995

Airblast overpressure legislative limits can be extremely difficult to meet throughout Australia, which has by far the most stringent limits of any nation in the world. As the difficulty in meeting the limits is strongly dependent on the scale of mining, it is not surprising that the Australian coal mining industry is experiencing particular difficulties in meeting these limits. Eight full scale overburden blasts have been modelled with respect to overpressure impact for a strip coal mine, involving both dragline (cast) blasting and pre-strip (non-cast) blasting. Overpressure levels in the range 100 to 125 dBL have been measured at distances varying from 2.4 to 5.7 km, and modelling has successfully estimated both the amplitude and shape of overpressure waveforms to within an average of 1.2 dBL. Typical errors of prediction are around 0.6 dBL. This accuracy of prediction has been achieved by considering the impact of only the face holes, and the accuracy of prediction of both shape and amplitude suggests that it is these holes which dominate the environmental overpressure impact at distances in the range two to six kilometres, for cast and pre-strip blasting operations. Modelling has been based upon the Elemental Overpressure Wavelet proposed by Richards and Moore (2002), incorporating actual hole coordinates, actual delay timing, and assumed delay scatter statistics. The incorporation of delay scatter statistics has been particularly significant, and allows the determination of the range over which the peak overpressure levels are expected to vary. To date, modelling has considered only the use of conventional pyrotechnic delays, though simple adjustment to the scatter definition would allow estimation of overpressure levels, and their variability, with electronic delays.

Jan 1, 2004

By Y. J. Wang

Editor's Note: Y.J. Wang's paper appeared in the September Technical Papers section. There were some inadvertent editorial errors in it. So we are reprinting it here. Abstract - This paper examines the ventilation network problem from a view point of solving a system of B equations in B unknowns, where B is the number o f branches in the network. Based on Kirchhoff s current and voltage laws, the solution to the general ventilation network problem must satisfy B network equations. In this paper, the air quantities and control-device pressures are chosen as variables and are grouped into B dependent variables (unknowns) and B independent variables, resulting in a system of B equations in B unknowns. Based on whether their variables are dependent or independent, the network branches are classified into f our types: five d, non-fixed, p-fixed, and q fixed. The ventilation network problem may include all four types of branches. There are .some conditions under which the problem as defined in this manner does not have a unique solution. To have a unique solution, the Jocabian matrix of the equations m us! he nonsingular. It then follows that: • the number of branches with independent air quantities must be less than or equal to the number of chords with respect to a spanning tree; •the subnetwork of branches with independent air quantities must not contain any cutset; and •the suhnetwork of branches with dependent control-device pressures must not contain any cutset. These three conditions must be met regardless of the values for the variables. In addition to the problem formulation, a solution procedure applying the Newton (or Newton-Raphson) method is outlined and illustrated with an example problem.

Jan 1, 1991

By Joseph Pogue

IT IS well known that one of the cornerstones of economic theory is the so-called law of supply and demand, which, really, is a group of economic laws, one of which may be succinctly stated : A rise in price tends, sooner or later, to increase supply. It is the fear that, in the case of petroleum, a limited natural resource, a point will soon be reached when supply will not respond adequately to price advances, which in recent years has prompted a movement for oil conservation. This movement has lately taken concrete shape in the appointment of a Federal Oil Conservation Board by the President. An important aspect of the law of supply and demand is that the supply of any commodity is not an entity per se, but is a factor of price. Supply, without the specification of price, has no exact meaning; and in practice supply cannot be divorced from considerations of price. Mathematically, supply may be expressed by the formula SP, which means that supply varies with price, just as the value of 10 raised to the x power varies with x. In its technical usage, supply is the quantity of a commodity that is bought currently on the market at a given price. In the case of a natural resource, however, this quantity will eventually depend not alone on price but on the physical volume of the reserve that exists and. that, in consequence, can respond to the stimulus of price. If this reserve is fixed in size, we must sooner or later reach a point where supply can no longer respond to price in the usual degree and a permanent shortage. will develop which no advance in price can correct, except in so far as higher prices may curtail demand or improve the efficiency of utilization.

Jan 3, 1925

By Maria I. De Rosa

Table 28 and figure 10 show the number of fires and fire injuries for coal preparation plants by state during 1990-1999. Table 28 also shows the risk rates, employees' working hours, and lost workdays by state. For coal preparation plants, 91 fires occurred in 1 1 states during 1990- 1999. Twenty-three of those fires caused 25 injuries (the yearly average was 9.1 fires and 2.5 injuries). Ten fires and eight injuries involved contractors. The Ewhr value was 24 1 x 10' hr (Irr = 0.02 l), and the LWD value was 198. Pennsylvania had the most fires (24 fires and 4 injuries), whereas West Virginia (22 fires and 7 injuries) and Kentucky (22 fires and 7 injuries) had the most fire injuries. Among these states, Kentucky had the highest injury risk rate value (Irr = 0.025). Table 29, partly illustrated in figure 11, shows the number of fires, fire injuries, risk rates, employees' working hours, and lost workdays by time period. The number of fires decreased during most of the periods (an increase is seen only during the last period). The number of fire injuries show a decrease followed by an increase during the periods, accompanied by a decline in employees' working hours throughout the periods. The Irr values follow patterns similar to those shown by the injury values (see table 29 and figure 11). Tables 30-35 show the number of fires by ignition source, method of detection and suppression, equipment involved, location, and burning material by time period. Figure 12 shows the major variables during 1990-1999. Table 36 shows the fire injuries per number of fires causing injuries and total fires by year, ignition source, equipment involved, and location.

Jan 1, 2004

By Charles R. Keyes, D. F. Riddell

For a period of several years, and in a large number of oases, the Metallurgical Laboratories of the New Mexico School of Mines were employed in umpire work. During this time many important local problems mere solved. Against the results of careful chemical analyses of ores, assay-returns mere often checked. In many cases the assay-methods of mine and custom-smelter were compared, and both often found faulty for the ore concerned. A wide range of ores was covered. Many of the chemical analyses and assays were made by Dr. F. C. Lincoln, Professor of Metallurgy, now of the Montana State School of Mines. A varied series of instructive assays was prepared by Prof. R. B. Brinsmade, now of the West Virginia State University. Single assays and given series of tests were undertaken by H. T. Goodjohn, now chief chemist to the Cia. Metalurgica de Torreon, Coahuila, Mexico; by H. J. Hub-bard, now superintendent of the Butters Divisadero Mines, Jocoro, San Salvador, C. A.; by E. D. Morton, now superintendent of the Arizona & Nevada Copper Mining Co., at Lunning, Nev.; and by A. W. Edelen, now superintendent of the Angangueo Unit of the American Smelting & Refining Co., in Michoacan, Mexico. A critical comparison of assay-methods that were found to be followed in the case of certain gouge-ores mined in the Mimbres range in New Mexico, and about which there had been much controversy, was made by D. F. Riddell, then Acting Professor of Assaying, and now superintendent of the Providentia Mines Co. of Parral, in Chihuahua, Mexico. To him is due the credit of much that is contained in the following notes, which he has generously permitted to be used in advance of the publication of the complete results.

Jan 1, 1912

By G. A. Reinhardt

THE Youngstown Sheet & Tube Co. has produced a large tonnage of 0.35 to 0.45 carbon forging steel, the acceptance of which was based on the physical properties of test specimens obtained by forging the original 5 3/4 in. (14.5 cm.) square bloom to a ¾ in. (1.9 cm.) round. Annealed and tempered specimens were required. The test bars were annealed by heating from 900 ° to 950° C. and cooling slowly in mica. The test bars were tempered by heating to 825° to 875° C., quenching in water, and drawing to 515° to 535° C. Immediately after heat treatment, the test pieces were machined to a diameter of 0.534 in. (1.38 cm.) and tested. Very good physical properties were obtained and no difficulty was experienced in meeting the specifications called for. ULTIMATE STRENGTH, ELONGATION, LB. PER SQ. IN. PER CENT. IN 4 IN. NOT LESS THAN Annealed specimens 78,230 to 92,450 18 Tempered 120,000 to 149,350 9 After experience oil this material, production of slightly higher carbon forging steel was started. The method of testing this material required that test blooms be either normalized or annealed. The normalizing consisted in heating to 850° to 900° C. and cooling in still air; the annealing, in heating to 850° to 900° C. and cooling in the furnace or in mica. From the treated bloom, the test pieces were taken either by core drilling or by sawing from points midway between the edges and the intersection of the diagonals. The cores or blocks were turned to a standard 2-in. test piece with a diameter of 0.564 in. and tested without further treatment. The physical requirements of the test pieces were:

Jan 7, 1919

By Wilbur E. Sanders

At some period during the operation of metalliferous and other commercially valuable mineral-deposits in connection with their underground mining, when the developments therein have become so extensive that their description is tedious and confusing, some scheme for naming or numbering the various workings and their parts is necessary for convenience of reference. A simple and symmetrical yet expansive system of classification must be devised, one that is capable of being extended to cover all possible exigencies and conditions of future operations within the property. Such a scheme, properly arranged, greatly simplifies communication between the various departments of the mining business, as, for instance, between the administrative and the operating departments of the concern, and is of the greatest assistance to the officers of the mine in enabling them to locate and describe particular points and parts of workings and specific kinds of work. Again, in the proper segregation and differentiation of mine-accounts, when they are carried out with that detail which will furnish ready information concerning the cost of a particular piece of work, or the various items and totals of expense connected with the development, operation and repair of each or all of the mine-workings, some such method of clesignatioi~ becomes a necessity. Moreover, such a plan is acl- mirably adapted to the needs of the mining engineer, who, in connection with his reports upon mining-properties, is sometimes required, in his descriptions of certain blocks of ore, to locate lists of assays of samples taken from many and various places, and to designate workings and parts of workings that are located in different parts of the mine, sometimes at points wide apart. To write out in full a sufficient description of any particular

Jan 1, 1907

By C. N. Schuette

THE producers of this liquid metal call it quicksilver, while the consumer generally refers to it as mercury. It is one of he seven metals that were known to the ancients. These seven were gold, silver, iron, copper, quicksilver, lead, and tin. Other metals were sometimes accidentally alloyed with some of these, but it was not until 1490 that antimony, for example, was discovered and identified as a separate metal. It is not surprising that quicksilver should have been known in ancient or even in prehistoric times, as globules of the native metal often occur in the outcrops of the ore. Furthermore, the first man to build a fire on an outcropping of quicksilver ore would probably have found globules of quicksilver in the cold ashes of his fire after it burned out. The inability to pick up the globules with the fingers would excite interest and an attempt to gather it in shells or gourds to be exhibited and traded. The ore of quicksilver is the red sulfide, cinnabar, which has been mined and used as the pigment vermilion since before the beginning of written history. In recorded history, quicksilver is first mentioned in documents by Aristotle, 384-322 B.C. Theophrastus, in 315 B.C., credited the Athenian, Callias, with the invention of methods to beneficiate cinnabar in 415 B.C. In China also there are records antedating Christ which mention both vermilion paint and the fluid metal. From these early records, it seems certain that not only was cinnabar used as a pigment in those days but also that the metal was reduced from the ore and was used for amalgamation, for gilding, and for medicinal purposes. Quicksilver mining and metal-

Jan 1, 1953

W. ROWLAND Cox,* New York, N. Y. (written discussion?).-The process described by Mr. Malcolmson undoubtedly represents a great stride toward conservation of our natural resources. Without discussing the subject from an economic standpoint, I wish further to emphasize the fundamental principles of the Smith process in order that its economic value may be fully appreciated. The process is essentially a means of producing an ideal fuel, as regards its combustion qualities, by the removal of the so-called volatile matter from the coal, in the form of byproducts, which have value for other purposes far in excess of their fuel value. In other words, coals which contain. large amounts of gas, tar, and ammonia, and are not suitable for domestic or industrial fuel, or for treatment in byproduct coke ovens or gas retorts; because they possess poor coking qualities, can he prepared for commercial use by the. Smith process with a very high degree of efficiency. Much work has been done along this line, both in this country and in Europe, in developing a means of preparing coal, as the economic advantages have long been recognized. To the best of my knowledge, the Smith process is the only one that has proved its commercial adaptability. Distillation of coal at 900° to 1000° F. (480° to 540° C.) yields a large amount of tar and oils. The residue of the distillation, however, is a very friable semi-coke, wholly unsuitable for use as a fuel, unless it can be charged directly into a byproduct gas producer. The problem which confronted the inventor was then to convert this carbon residue into a commercial product, and it is in this step that the Smith process has overcome the obstacles which prevented a number of other methods from becoming commercially practicable.

Jan 10, 1918

'Industrial Minerals - their mining and use in New Zealand' is the theme of the 1978 Annual Conference of the New Zealand Branch of The Australasian Institute of Mining and Metallurgy. This paper describes the use of phosphate rock, sulphur and potassium chloride (potash) - three industrial minerals which have enabled the farmers of New Zealand to increase production to current levels. The growth of imports of these raw materials for the New Zealand fertiliser industry is well documented in NZ Fertiliser Statistics 1977. This is the most recent of the Ministry of Agriculture and Fisheries annual publications on this Subject prepared from the detailed returns of fertiliser manufacture and sales from each fertiliser works. There are now 12 of these works in New Zealand one of the most recently established being in Whangarie where this conference is being held. Its capacity to manufacture superphosphate will shortly be 300 000 tonnes twice that when it opened late in 1964. New grinding and manufacturing equipment comes on stream early in 1979. This paper illustrates the interdependence of two primary industries, agriculture and mining. New Zealand's economy in the foreseeable future will be based on agriculture so that our standard of living is dependent on the overseas prices and freight costs of the bulk raw materials from which our fertilisers are made. For the year ended 31 March 1978 New Zealand's total exports were $3395 million, of this total $2413 million (71%) came from the products of pastoral agriculture (wheat, wool, dairy and other animal products), $291 million from forest products and $501 (15%) from manufactured exports. Approximately half of the pastoral receipts can be attributed to the fertilisers applied at a total cost of about $200 million including subsidy.

Jan 1, 1978

By D. B. Dow

"Natural gas-gasoline is made by collecting in the liquid state the condensable hydrocarbon vapors that exist in different natural gases in varying amounts. In the richer type of natural gas the gasoline is generally recovered by compression and cooling. If exceedingly high pressure or low temperature is used, there is dissolved in the gasoline a large amount of very volatile material, which evaporates rapidly at atmospheric temperature and pressure.In the leaner type of natural gas, the gasoline vapors are selectively absorbed from the permanent gases by passing the natural gas through an absorbing oil. The gasoline is recovered by distilling the saturated oil, and as compared with ""compression"" gasoline is of high Baume' gravity and low vapor pressure. Before a volatile gasoline can be transported in tank cars, it is necessary to decrease its volatility in order to lessen the risk of fire or explosion, as well as to prevent excessive evaporation in transit. This can be accomplished either by weathering the gasoline, or by blending it with a more stable material, naphtha being commonly used in the weathering process the more volatile portions of the gasoline are allowed to evaporate and the losses in volume are very large, therefore, blending is preferable, wherever possible.It is very difficult, however, to produce by blending, in gasoline plants, a motor fuel which is equal to straight-run refinery gasoline. In order to make a blended motor fuel of a grade equal to straight-run gasoline, only a small percentage of natural gas-gasoline can be blended with the naphtha, consequently it is customary to blend the gasoline with only enough naphtha to enable It to be shipped to an oil refinery when the material is again blended to form a finished motor fuel."

Sep 1, 1921

By Robert A. Haney, Richard T. Stoltz

In July, 1988, the Mine Safety and Health Administration (MSHA) Advisory Committee on Standards and Regulations for Diesel-Powered Equipment in Underground Coal Mines recommended that the Secretary of Labor set in motion a mechanism whereby a diesel particulate standard can be set. Prerequisite to establishing a standard would be the development and evaluation of instrumentation to measure diesel particulate. In response, the Mine Safety and Health Administration, Dust Division, has been evaluating instrumentation that can be used to determine diesel particulate levels in underground mines. This instrumentation employs the principle of impaction to separate particles by size, thereby, separating the diesel and nondiesel particulate. Separation of the particulate by size was chosen because diesel particulate is generally less than 1.0 micrometer in size. No other methods have been developed to successfully distinguish between the coal and diesel particulate. MSHA developed an impactor that is inexpensive and compatible with existing pumps and filter holders. The instrumentation evaluation has primarily focused on the repeatability and performance of several personal dust samplers. The samplers tested include the Sierra-Andersen Model 298 personal impactor and MSHA developed personal impactor. The MSHA impactor is inexpensive and compatible with the existing pumps and filter holders. In addition to evaluating the precision and performance of these instruments, tests have been conducted to determine background levels of submicron particulate in nondieselized coal mines and to measure the submicron particulate content in dieselized coal mines. Tests were conducted in coal mines where diesel equipment was used only in outby areas and also in coal mines where diesel equipment was used for face haulage. This paper describes the results of the tests and provides a description of the instrument at ion used to conduct the tests.

Jan 1, 1989

By Frank E. McCall, John K. Marshal, Fred Garcia

Since the advent of longwall mining systems in the United States, mine operators are increasingly relying on methane drainage techniques to supplement the ventilation system. The most commonly used technique is the vertical gob borehole. The number and spacing of vertical gob boreholes per panel is generally based on experience and underground conditions. To design a more efficient methane drainage systems, mine operators must accurately determine methane gas produced. Thus, mine operators must monitor gas flow and methane gas concentration on every vertical gob borehole on active panels at least once or twice during each 8-hr shift. As the mine grows, it is possible to have more than one operating longwall and many vertical gob boreholes. Thus, daily visits to each vertical gob borehole site can become very time consuming. During weekends when methane gas concentrations typically drop because there is no mining activity, borehole sites may not be visited. To obtain accurate gas flow data, a gob borehole monitoring system was designed and constructed by the U.S. Bureau of Mines (USBM). Gas flow, methane gas concentration, gas temperature, barometric pressure, and vacuum pressure of the exhaust fan are the parameters collected by the system. The system also includes circuitry for automatic shutdown of the exhaust fan and an alarm system before an unsafe condition is created. Telemetry components were also integrated into the system to allow for transmission of borehole data to the mine office. As a test, the system was installed and operated on a vertical gob borehole for six months. Test results indicated that intermittent measurements with hand-held instruments from vertical gob boreholes were always higher than gas flows measurements made by the gob gas analyzer system. This paper describes the system components, operational characteristics, and the results of the test program.

Jan 1, 1995

By J. F. Archibald

It is often alleged by mine ventilation engineers that no reliable method exists to forecast the levels of radiation to be encountered in future uranium mines. It results that the design of uranium mine ventilation systems is based on factors other than radiological hazards, such as radon and radon daughter concentrations, for which permissible limits are set. Ventilation has been used to date as the main control mechanism for radon and radon daughters. Although it has become increasingly difficult to provide enough ventilating air to reduce the radon gas and its daughter products to safe levels in some mining arrangements, it is not the object of this paper to discuss alternatives to ventilation. This paper will describe a methodology followed by the authors over the years to estimate the levels of radiation to be encountered in underground and open pit uranium mines. Ventilating air is used to maintain working level concentrations within safe limits. The sources of radon and radon daughters and the quantities of each which will be produced, will be of great value in planning and designing a ventilation system to control them. This information can afterwards be integrated into the overall mine design. The methodology to be outlined can also be used to estimate, given a mine design format, the radiation levels to be encountered. If levels are not acceptable, modifications in the mine design can be made at an early stage. The emphasis is placed on an integrated effort where the ventilation engineers and the mine design engineers work in close collaboration from the very start of the mining project. Estimation of radon and radon daughter levels can be initiated as soon as core samples are obtained from the exploration programmes.

Jan 1, 1980

By E. J. Dulis, V. K. Chandhok, J. P. Hirth

Cobalt clearly increased the activity of carbon in austenite and in ferrite. This effect of cobalt on carbon activity Plausibly accounted for the effect of cobalt on accelerating the austenite to pearlite transformation. Cobalt was found to have only a slight effect on carbon diffisivity in various Fe-Co and Fe-Co-W-Mo austenites, but was found to decrease carbon diffusivity in Fe-Co ferrite. THE effect of cobalt in steel is unique in that it is the only element that reduces hardenability by accelerating the austenite to pearlite reaction. The results of several excellent investigations aimed at explaining the role of cobalt have been published,1"7 but a complete understanding is still lacking. In addition, cobalt significantly enhances the resistance to softening or tempering of highly alloyed highspeed and hot-work tool steels. The resistance to tempering is related to the secondary hardening reactions associated with the fourth stage of tempering during which carbides of molybdenum, tungsten, and/or vanadium form in a martensite matrix. The effect of cobalt on secondary hardening reactions in high-alloy tool steel has received considerable attention, but a full explanation of the reactions involved has not been developed. Inasmuch as austenite to pearlite transformation and secondary hardening involve carbide formation, the present authors believed that the role of cobalt in effecting carbon activity and diffusivity in austenite and in ferrite was important to a fuller understanding of the phenomena involved. TO investigate the effect of cobalt on the activity coefficient of carbon in austenite, an approach was used similar to that used by Darken17 in his experiments on the effect of silicon, manganese, and molybdenum on carbon activity and diffusivity in austenite. TO

Jan 1, 1962

By Roshan B. Bhappu

Selenium is found most frequently as an accessory mineral in the ores of lead, copper, and nickel, and is recoverable as a byproduct in the treatment of many of the ores of these metals. The geographic distribution of the selenium industry closely follows that of electrolytic copper, with the United States and Canada producing approximately 75% of the total output of the non-communist world. This situation is problem number one for selenium-its dependence upon the electrolytic refining of copper- for this byproduct source is not sufficiently flexible to permit a normal supply-demand balance. Furthermore, selenium has become a strategic material in short supply. Thus, new sources are being sought by both government and private interests. Although considerable attention has been given to this effort during the last few years, hardly any research has been published concerning the recovery of small amounts of selenium present in low-grade deposits. In such ores the metal occurs as native selenium or as selenides of iron, copper, silver, lead, and bismuth. In recent years, some native selenium (in both the gray and red form) and selenides, especially iron selenide (ferroselite), reportedly have been found in the sandstones of the Morrison formation near Grants. New Mexico. Similar occurrences have been reported in the Hagan coal basin, in Sandoval County, New Mexico. Samples from New Mexico ores have contained from a trace amount to as high as 0.425% Se. Some of the samples from uranium mines in the Grants area represent mixed ore and mill feed fur uranium reduction plants. In such cases, the selenium usually is reported as an impurity and is lost in the tailings. At present, no attempt is made to recover this waste metal.

Jan 8, 1962

By D. C. Torre

Ever since the introduction of the first successful continuous mining machines some twenty odd years ago, there has been an obvious, and steadily increasing, need for some form of continuous haulage machine, or system to work with them. There is universal agreement that the continuous mining principle, and the various continuous mining machines in particular, have done a great deal for mining. However, coal mining men, who have the longest and broadest experience with them, agree that continuous miners do not truly mine continuously. In fact, their estimates, and actual studies, show that the real mining time of these machines ranges, on the average, from 20% or less to about 30% of the available shift time. Part of the failure of the continuous mining machine to mine continuously may be ascribed to breakdowns in its intricate machinery. Most of the failure, however, is blamed on a variety of other factors. Of these, there are two which are given particular blame: face haulage and roof control. The relative importance of the two as the major negative factor in continuous mining is a moot point. However, there is an extensive concensus that haulage is the number one problem. Roof problems and their control are inhibiting factors regardless of the type of mining or mining machines employed. But the truth of the matter is that a continuous mining machine, like any type of loading machine, whether underground or on surface, is only capable of mining or producing in direct ratio to the mineable, or loadable, material that can be kept ahead of it and equally, if not more, important, that can be taken away from it. While the first commercially successful continuous miners were developed for, and proved successful in, coal mining, they were soon

Jan 1, 1974