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By T. E. Leontis

The specific effect of various rare-earth metals on the room- and elevated-temperature properties of magnesium has been evaluated. Alloys containing didymium exhibit the highest tensile and compressive strengths at room and elevated temperatures. All the rare-earth metals increase the creep resistance of extruded magnesium at temperatures in the range of 400° to 600°F, but the degree of enhancement depends on the temperature and on the concentration of the added metal. THE effects of rare-earth metals on the properties of sand-cast magnesium were discussed in some detail in earlier paper by the author.' The present paper deals with the effect of the same alloying elements on the properties of extruded magnesium. This investigation also had as its aim the development of a wrought alloy having a better combination of room-temperature strength and ductility and elevated-temperature strength and creep resistance than is found in magnesium-Mischmetal-manganese alloys, which have been reported earlier.2-5 The only known attempt to study wrought magnesium alloys containing pure cerium instead of Mischmetal was made by Mellor and Ridley.6 They found that in the form of rolled bars there is a definite, optimum cerium content for creep resistance at 200 °C and that the creep resistance of these alloys at 200 °C is significantly Improved by heat treatment at 550" to 580"C. In the present investigation the compositional variation in mechanical properties of the following alloy systems is presented: I—magnesium-Misch-metal. 2—magnesium-cerium-free Mischmetal. 3— magnesium-didymium. 4—magnesium-cerium. 5— magnesium-lanthanum. Alloys containing predominately praseodymium are not included in this series because of the lack of this material. Experimental Procedures The alloying ingredients used in preparing the alloys described herein are the same as those reported in the earlier paper.' Cerium-free Mischmetal is the rare-earth mixture remaining when the cerium is removed from Mischmetal, which contains all the rare-earth metals as they occur naturally in mon-azite sand, the ore from which Mischmetal is produced. Removal of both cerium and lanthanum from Mischmetal leaves what is commonly called "didym-ium," consisting predominantly of neodymium and praseodymium. Although the composition of the particular batch of each metal used may differ somewhat from the analysis presented previously, these differences are not great enough to warrant repeat- ing the specific composition of each material. The electrolytic magnesium used as the starting material in these alloys has the same typical analysis as that given in the earlier paper.' The alloys were prepared in small laboratory melts applying all the necessary precautions for alloying rare-earth metals with magnesium described by Marande.' Most melts were large enough to cast one 3 in. diam billet 10 in. long. In a few cases, particularly the didymium-containing alloys, the lack of sufficient amounts of the rare-earth metal limited the size of the billet to 6 to 8 in. All billets were scalped to a diameter of 2 15/16 in. and faced to a length of 9 ¼ in. as limited by the size of the extrusion container. The alloys were extruded into ½ in. diam rod on a 500-ton direct-extrusion press using a 3 in. container. The details of the extrusion step are: billet preheat, 925°F (2 hr); container temperature, 900°F; die temperature, 900°F; extrusion speed, 10 ft per min; reduction ratio, 36:1; and percent reduction, 97.3. The lower melting point of alloys containing didymium' necessitated reduction of the extrusion speed to 5 ft per min in order to prevent hot shorting during extrusion. Adequate lengths were cropped from both ends of each extruded rod to assure that all the material used for tests was extruded under uniform conditions. Tensile and compressive properties at room temperature are reported in the several conditions of heat treatment. The ASTM designations are used to distinguish these conditions as follows: T5—Direct age at 400°F (16 hr) T4—Heat treat at 950°F (4 hr) for alloys containing didymium T4—Heat treat at 1050°F (4 hr) for all other alloys T6—T4 + age at 400 °F (16 hr) The lower heat-treating temperature for alloys containing didymium is necessitated by the lower melting point of these alloys. All heat treatments were conducted in electrically heated, circulating-air furnaces. A protective atmosphere containing 0.5 to 1.0 pct sulphur dioxide was used for the high temperature heat treatments. Tension and creep specimens 6 Yz in. long and compression specimens 1½ in. long were cut from the extruded rod. A reduced section of ? in. diam was machined on the tension specimens, whereas on the creep specimens a reduced section of 0.450 in. diam

Jan 1, 1952

By Kenneth A. Gutschick, Robert S. Boynton

Lime has become a general and loosely used term to denote almost any kind of calcareous material or finely divided form of limestone or dolomite, as well as burned forms of lime. However, according to Webster, lime is only calcined limestone (known as quicklime, unslaked lime, or calcium oxide). It also embraces the secondary product of quicklime, i.e., hydrated lime or slaked lime (calcium hydroxide). There are two basic types of limestone used for lime manufacture-high calcium and high magnesium (dolomitic). The dolomitic quicklimes and hydrated limes correspond to their "high calcium" counterparts. The only difference is that the dolomitic types are a combination of the elements calcium and magnesium, in varying percents, whereas high calicum limes contain less than 5% MgO down to 1/2%. In either case a pure form of limestone of at least 97% combined carbonate content is needed to make salable lime, barring a few exceptions. The calcination of both types is diagrammed chemically as follows: [ ] In the foregoing reversible reactions the limestone is burned (calcined) in lime kilns, with the carbon dioxide content of the stone expelled as a gas. The weight loss during calcination of pure high calcium limestone is 44%; with equimolecular dolomitic limestone, the weight loss is 48%. Since lime has a strong affinity for CO_, particularly if moisture is present, it will readily revert to its original carbonate form. This occurs when quicklime "air-slakes" and adsorbs CO.. from the air. Thus, quicklime is perishable and should be stored in dry, water-tight areas. Depending upon the type of kiln used and the physical structure of the stone, the size of the quicklime may range from sandlike granules to 8 in. lumps. However, pebble sizes ranging from 1/4 in. to 2 in. are the most common. Screened quicklime fines are also com¬pressed (pelletized) into 1 in. pellets. For some purposes ground or pulverized forms of quicklime are used, ranging from No. 10 mesh to dust. Generally a pebble of quicklime is about the same size as the pebble of limestone before calcination (perhaps shrinking slightly). A more stable form of lime is hydrated lime. This is obtained by adding water to quicklime, slaking it into a dry, fine, subsieve size white powder. Because its affinity for moisture has been satisfied, it is not vulnerable to further moisture like quicklime. However, it has the same strong affinity for CO_. The following reversible chemical reactions illustrate how hydrated lime when heated (or dehydrated) can revert to the original oxide form:

Jan 1, 1975

By Henry F. Cooper, Scott E. Blouin

Large jacking test procedures that have been applied to obtain static in-situ rock properties (Ref. 1) have shown that the in-situ rock modulus and strength can be considerably less than what would be obtained from laboratory tests on intact samples. This trend is also expected to be true for dynamic properties, but few dynamic in- situ rock property tests have been conducted. During the past several years, high explosive test procedures have been developed to simulate the airblast and direct induced ground motions (Ref. 2) produced by nuclear explosions . These test procedures load large volumes (up to 10 7 f t3) of the earth with stress levels sufficiently high to produc5 feet of particle displacement over surface areas up to l0 5 ft2. This paper discusses some of the data obtained, and the implications of these results for our understanding of the dynamic response of in-situ rock. DESCRIPTION OF TEST PROCEDURES As shown in Fig. 1, the High Explosive Simulation Technique (HEST) consists of a cavity of uniform height bounded on the sides by a soil berm, above by an overburden of uniform thickness, and below by the test bed on the earth's surface. Horizontal racks of detonating cord are placed in the cavity and detonated at one end of the test bed. This detonation produces an explosive wave that propagates across the test bed, loading the earth with an overpressure pulse that decays with time because of the compression and lifting of the overburden. Since 1964, there have been approximately 40 such tests on test bed areas ranging from a few hundred to l0 5 sq ft., simulating peak overpressure conditions between about 100 and 6000 psi and specific impulses between a few and over 100 psi-sec.

Jan 1, 1971

By S. L. Hoyt

The writer has long been interested in seeking an explanation of the upper heat effect in the copper-tin alloys over the a + b range, first described in 1913. These notes are offered, not at all as the final explanation 'of this heat effect, but rather to indicate certain progress which has been made toward establishing what happens over this temperature interval. While working on the thermal analysis of the copper-rich kalchoids (copper-tin-zinc alloys), it was noted that those alloys containing major portions of tin and minor portions of zinc exhibited two marked heat effects, one at about 520' C. and the other at about 600" C., instead of the single effect which is generally observed in either of the two binary series. This matter was discussed with Dr. Guertler, who suggested that a heat effect at about 600" C. in the pure copper-tin alloys might be expected. This led to a more searching examination of the thermal critical points in the pure copper-tin alloys, with the result that a marked, although somewhat weak, heat effect was located at about 600. Somewhat later, this upper heat effect was discussed with Dr. Burgess, and it was requested that the Bureau of Standards make heating and cooling curves of one of these alloys for the purpose of removing any possible doubt as to the actual presence of the heat effect. Results obtained by the Bureau are given in Plate I. In an earlier paper1 differential curves were published showing that the heat effect occurred at constant temperature over the a + B range and increased in magnitude with the amount of B up to a point somewhat above 20 per cent. tin. No heat effect was noticed at this temperature in the eutectoid alloy. The existence of this heat effect seems to require a modification of the present copper-tin diagram in the a + B field, and it has been the object of the work here presented to secure the evidence upon which such a change should be based.

Jan 1, 1919

By Daryl R. Tweeton, Jerry R. Riding, Grant Buma, Frank J. Rosswog

In situ solution mining of uranium has environmental advantages over conventional mining. The leaching of uranium, however, alters the ground-water quality in the aquifer where the mining occurs. Currently, regulations require that the ground water be restored to approximately its original condition. This paper, a summary of a study funded by the Bureau of Mines, reviews the state of the art in restoring ground-water quality after in situ uranium leaching. Current restoration practices discussed include disposal of liquid wastes in deep disposal wells and evaporation ponds, producing from all wells during restoration, and recirculating water purified in surface plants. Methods for predicting the effectiveness and cost of current techniques are presented. Possible alternative techniques are also described. Two restoration operations are discussed.

Jan 1, 1979

By William D. Klopp

A study was conducted of the tensile and creep properties of are-melted and electron-beam-melted tungsten over the temperature range 2250° to 4140°F. The tensile and creep strengths vary with pain size, the finer -grained materials being stronger. The activation energy for transient creep at 2250° to 3500°F is 95,000 cal per (g)(mole), while that for steady creep at 3300o to 4000°F is 141,000 cal per (g)(mole). At 2875o to 3300°F the apparent activation energy for steady creep decreased with decreasing temperature. It is suggested that cross slip is rate controlling during transient creep, while dislocation climb is rate controlling during steady creep above 3300° F. ALTHOUGH considerable data have been generated on the high-temperature tensile properties of powder-metallurgy tungsten,1 relative few data have been published on the properties of are-melted2 or electron-beam melted tungsten.3 Furthermore, the available data show a fairly large amount of scatter at high temperatures. The effects of structure and purity have not yet been defined, aside from observations that high-purity electron-beam (EB)-melted tungsten3 and single-crystal-plasma-flame tungsten4 are weaker than less pure powder-metallurgy tungsten. The creep behavior of powder-metallurgy tungsten has been studied, but no data are available on the creep behavior of tungsten consolidated by melting. Green5 found that powder-metallurgy tungsten exhibited linear creep at 4082° to 5072°F with an activation energy of 160,000 cal per (g) (mole). The similarity of this activation energy to that of 153,000 cal per (g)(mole) for volume self-diffusion6 suggests that recovery of strain hardening by dislocation climb is rate controlling in this temperature range. In studies at 4800°F, Sutherland and Klopp7 concluded that grain size significantly affected the creep behavior of commercial powder-metallurgy materials. This grain-size effect was suggested by sherby,8 although the opposite relation had been reported for aluminum.' The purpose of the present study was twofold: first, to provide baseline data on high-temperature tensile and creep properties of are-melted and EB-melted tungsten for concurrent tungsten alloy studies, and, second, to determine the phenomenolo-gical effects of structural and purity variables on the high - temperature mechanical properties of tungsten. EXPERIMENTAL The are-melted tungsten materials were prepared by melting sintered 1-1/4-in.-diam electrodes into 2-1/2-in.-diam by 5-in.-long ingots. The are-melting facility has been described previously.' Eight ingots were melted, machined, and hot-extruded at

Jan 1, 1965

By A. M. Gaudin

IN flotation lime is used to depress pyrite. For this purpose it is preferred to caustic soda. The low cost of lime and the widespread availability largely account for this preference. However, there is some evidence1 that pyrite is more readily depressed by calcium than by sodium ions at the same pH. To measure the difference in adsorption of calcium and sodium, which is thought to lie at the basis of the differences in depressing action, radionuclides of

Jan 2, 1953

By John Wulff, H. H. Uhlig

Since its first mention in the literature in the eighteenth century12 the phenomenon of passivity in metals has stimulated much speculation and attendant controversy as to its nature and cause. No one of the numerous theories so far proposed has been generally accepted. ‡ Faraday,' in 1836, associated the passivity of iron with a protective film over the surface of the metal, which materially prevents or slows down reaction with corrosive environments. His theory was that oxidizing acids like nitric acid form an unstable oxygen or oxide layer over the iron surface, which protects the underlying metal from further attack. This concept was simple yet plausible, and without alteration has frequently been assigned in present-day discussions as explanation of the passivity of many metals. With the advent in recent times of stainless steels, it is not surprising that this oxide film theory of passivity proposed by Faraday has been used to explain the phenomenal corrosion resistance of stainless steels and other passive alloys. The passive alloys, such as the chrome-iron alloys, are supposedly covered with a protective oxide film, which forms on exposure of the alloy to air, is extremely stable and self-healing, and accounts for the remarkable resistance of these alloys to corrosion. Within the past few years, several investigators, following the theory of film protection, have attempted to gauge the resistance of the supposed film on steels. Brennert8 and Donker and Dengg9 determined the potential at which a negative ion (e.g., C1-) moving in an electric field reacted with the metal anode, as detected by increased current flow or change in potential of the steel electrode in an electrolytic cell. The potential corresponding to reaction Brennert called the film break-through potential.

Jan 1, 1939

By John Wulff, H. H. Uhlig

Since its first mention in the literature in the eighteenth century12 the phenomenon of passivity in metals has stimulated much speculation and attendant controversy as to its nature and cause. No one of the numerous theories so far proposed has been generally accepted. ‡ Faraday,' in 1836, associated the passivity of iron with a protective film over the surface of the metal, which materially prevents or slows down reaction with corrosive environments. His theory was that oxidizing acids like nitric acid form an unstable oxygen or oxide layer over the iron surface, which protects the underlying metal from further attack. This concept was simple yet plausible, and without alteration has frequently been assigned in present-day discussions as explanation of the passivity of many metals. With the advent in recent times of stainless steels, it is not surprising that this oxide film theory of passivity proposed by Faraday has been used to explain the phenomenal corrosion resistance of stainless steels and other passive alloys. The passive alloys, such as the chrome-iron alloys, are supposedly covered with a protective oxide film, which forms on exposure of the alloy to air, is extremely stable and self-healing, and accounts for the remarkable resistance of these alloys to corrosion. Within the past few years, several investigators, following the theory of film protection, have attempted to gauge the resistance of the supposed film on steels. Brennert8 and Donker and Dengg9 determined the potential at which a negative ion (e.g., C1-) moving in an electric field reacted with the metal anode, as detected by increased current flow or change in potential of the steel electrode in an electrolytic cell. The potential corresponding to reaction Brennert called the film break-through potential.

Jan 1, 1939

By M. Kaitz

A continuing discussion in both the petroleum engineering and economic literature is directed to the difficulties encountered in the use of discounted cash flow rate of return (DCF) as a measure of investment worth. Although useful in most Instances, DCF has been criticized because it is time-consuming in its trial-and-error solution, theoretically invalid, not adaptable to cash flow streams yielding multiple return solutions and not entirely reliable in selecting between mutually exclusive investments. The theoretical invalidity of DCF stems from the reinvestment assumption implicit in the calculation that earnings are reinvested at the DCF rate. The emerging consensus of the economic literature is that the net present value or the present worth of the net cash flow stream (discounting at the average opportunity or cost of capital rate) is more correct and reliable. Other criteria proposed have been ratios of net present value divided by initial investment or by present value of all investments in a project. All of these criteria are simple to determine and explicitly assume a reinvestment rate for [he income generated by a project. This paper develops and discusses a theoretically valid profitability criterion which is simple to compute and retains the appeal of a percent return on investment. It is called "percentage gain on investment" or PGI. It measures the gain an investment is expected to realize over like capital invested in the average opportunity and explicitly considers reinvestment potential. Why add another Concept to the large array of investment criteria now available, any one of which, or perhaps a combination of several, appears to embrace the form's (or individuals) objectives? The answer is that not one of the existing criteria provides both a readily comprehensible and theoretically valid measure of risk coverage that has general application. The proposed PGI does fulfill these requirements. INTRODUCTION An ancient expression warns that "one must yield to the times" — there are better ways of doing things. A review of the petroleum engineering and economic literature on one topic alone, measurement of investment worth, certainly is witness to this truth. In use for a number of years, the DCF has recently received attention, directed mainly to its theoretical invalidity. Several alternatives to DCF have been proposed to provide a valid, simply determined criterion to describe investment worth and to overcome the criticisms previously mentioned. This paper introduces another method called percentage gain on investment (PGI) and is proposed as but one of several yardsticks that should be used in making investment decisions. MEASURES OF INVESTMENT WORTH This paper will consider only those criteria which give weight to the time pattern of future earnings. These criteria are usually compared with an average opportunity rate or cost of capital of the firm to judge the relative worth of the investment. For purposes of demonstration, a 9 percent average opportunity rate will be used throughout this paper. Implicit in the DCF calculation is the assumption that earnings are reinvested at the DCF rate. Some argue, though, that there is no reinvestment assumption,' that the DCF rate is simply that maximum rate of interest one can pay on the investment over the life of the project and break even. The determination of DCF is accomplished by discounting the net cash flow stream at that rate (DCF) which will yield zero. The question is: why should reinvestment potential be explicitly considered in calculating return on investment or other criteria measuring economic worth? Perhaps the answer lies in consistent or equal treatment of future cash flow. It appears entirely illogical to give different present worth value to $1 received, say, 10 years from now, which is the circumstance resulting in comparing projects with different DCF returns. In fact, $1 received in 10 years has the same value regardless of which project generated the income. DCF return thus favors investment projects which are expected to provide early income as compared to those providing long-term income. Not surprisingly, the controversy on reinvestment assumption is an old one. Hoskold' discussed this same problem in 1877. He considered the future income from mineral properties as an annuity or a series of fixed future payments. (As will be demonstrated, his equation can be modified for variable income.) Prior to Hoskold, the value or what one could pay for the mine, was determined with the use of standard, single-interest tables. Here is what Hoskold said with regard to these tables. "This table, and others of its kind, to be found in most works on annuities, is constructed correctly according to

By Charles N. Bell

The Telluride mining district of southwestern Colorado is defined by the 37" 45' and 38" parallels of latitude and 107" 45' and 108" meridians of longitude. Telluride was never a boom camp, but has had a steady growth. In recent years, notwithstanding the business depression of 1920, the business has been the same as in normal years. The first prospector is said to have appeared in 1875, in which year locations on the Smuggler vein were made. Shipments were made in 1877 and 1878, and in 1879 milling the ores was attempted. While the district produced high-grade ores, it did not become important until 1890, when the Rio Grande Southern R. R. was completed from Ridgway to Telluride. The railroad has since been extended to Durango. In the fall of 1896, 400 stamps were in operation, and the annual production was $3,000,000.00, two-thirds of which was gold. The total production from 1875 to 1923 was: gold $58,274,527; silver 41,-830,920 oz., valued at $31,016,893; copper 15,258,866 lb., valued at $2,533,291; lead 166,056,484 Ib., valued at $8,324,910; zinc 18,141,182 Ib. valued at $1,323,787; or a total production of $101,473,408. All claims are held in fee. Most of them are 1500 by 300 ft. but claims located within the last few years are 1500 by 600 ft. General supplies are obtained at Telluride, Denver, and Salt Lake. The largest mines are within 6 miles of the town of Telluride. Denver is 422 miles and Salt Lake is 439 miles, by rail, from Telluride. One-half of the distance to Denver and one-sixth of the distance from Telluride to Salt Lake is by narrow-gage railroad. The labor is efficient. The best miners are Italians and Austrians, then Slavs, Greeks, and Mexicans follow in the order mentioned. There are no labor unions. There are no serious mine pumping problems, the drainage being through adits. The Tomboy and Smuggler companies pump water from their reservoirs, the former for milling and domestic purposes and the latter for milling, power, and domestic purposes. BIBLIOGRAPHY A partial bibliography of the Telluride District is: Geologic Atlas Telluride No. 57; Preliminary Report on the Mining Industries of the

Jan 1, 1925

By T. V. Falkie, D. R. Mitchell

Many operational problems in mine haulage cannot be solved economically by conventional analytic or trial and error methods. However, a method of probabilistic simulation, which is based on the fundamental assumption that many of the variables governing any physical system are probabilistic, has been adapted to certain areas of operations research in coal mine haulage. This paper attempts to illustrate how simulation can be used in basic haulage research and what kind of results can be expected. Optimization in this case is performed in terms of locomotive and car movement, as well as best utilization of men and equipment, and is approached primarily from the standpoint of scheduling of the main haulage. Many operational problems in mine haulage cannot be solved economically by conventional analytic or trial-error methods. However, a method of probabilistic simulation, which is based on the fundamental assumption that many of the variables governing any physical system are probabilistic, has been adapted to certain areas of operations research in mine haulage. In many physical cases several probability distributions interact with each other in special ways, and it is not possible to solve for their combined effect in a mathematical equation. This is often true in the case of mine haulage, where such variables as number of empties or loads per trip, travel times, and number of cars or tons produced in a given time are probabilistic. By using a simple example of one secondary haulage segment of a large underground haulage system, this paper attempts to illustrate how simulation can be used in basic haulage research and what kind of results can be expected. Optimization in this case is performed in terms of locomotive and car movement, as well as best utilization of men and equipment. This is the type of preliminary research that will be needed as a first phase in any major haulage study, whether it be a relatively simple economic analysis or a plan for complete automation. The problem of optimization has been approached primarily from the standpoint of scheduling of the main haulage. It is evident that the method of proba-

Jan 1, 1963

By J. Gross

G. H. Clevenger, Chairman of the Milling Methods Committee of the Institute, made the following introductory remarks: "Several years ago, a number of us felt that the time was ripe for a fundamental investigation of crushing and grinding. At the outset, it appeared that the first thing we needed was a yardstick whereby grinding efficiency could be measured. "The U. S. Bureau of Mines has been most generous in cooperating with the Milling Methods Committee in getting this work well under way. John Gross, who served the committee for a year as secretary, was placed in charge of the investigation and has been ably assisted by S. R. Zimmerley. "Messrs. Gross and Zimmerley will now present the Progress Report covering their work to date." PROGRESS REPORT J. Gross, Salt Lake City, Utah. -This has not been a simple problem, and when I tell you that we can give you a verbal report of what we have done during three years in five or ten minutes you will realize that we have necessarily done a great deal of work that does not appear in the final results. We have been in a virtually new field. Therefore, we have had to feel our way at each step so as to be fairly sure we were correct. The first thing that was realized in this problem was that unless we had some method of measuring what happened when we crushed an ore, we might as well quit and not go further. We realized that if we tried to measure the results of crushing or grinding by the ordinary sizing test we would not get anywhere. We could sieve down to say 200 mesh fairly accurately; we could even go one sieve size further with a little less accuracy, and then we were absolutely lost, unless we went into microscopic measurement. Even this latter method would not have been satisfactory. The question was: what were we going to measure? If we were going to measure size, we might measure one particular dimension of a particle and be off 200 per cent. or more. If we tried to measure surface, we would have something tangible; the surface of a particle, no matter how irregular, is something definite, far more definite than any linear dimension would be. Moreover, if we could measure surface, we would immediately have a method of checking the Rittinger law as to whether it was or was not correct. So the first thing that we sought was a method whereby we could measure surface on crushed particles or, we will say, on particles; it would not make any difference whether crushed or not. It then became a question of what kind of particles we were going to use in obtaining a method for surface measurement. We realized that it would be rather a com-

Jan 1, 1928

By M. D. Everell

A study has been made of the relationships between grinding selection functions and physical properties of rocks, particularly the failure loads of irregular particles and the compressive and tensile strengths of large regular specimens. The rocks used were limestones of various structures and impurity contents, a carbonatite, and a high-purity crystallized calcite. The selection functions were obtained from carefully performed grinding experiments on selected narrow size ranges in various grinding machines-a laboratory batch ball mill, a Hard grove grindability machine, and a mill of the type suggested by Yang, Mempel, and Fuerstenau. The specific rates of breakage during milling and the failure loads of irregular specimens correlated well for the rocks studied. The testing of irregular particles is suggested as a means of predicting the behavior of commercial mills.

Jan 1, 1973

By K. M. Kolobova, E. Z. Kurmayev, A. Z. Menshikov, S. A. Nemnonov, V. A. Trapeznikov

The present work represents a review of our intestigations into the X-ray spectra of solids, which have been carried out by us along two lines of upproach: 1) St@ of the electronic structure of high -rnelting compounds of transition metals; 2) stzddy of the interatomic binding forces by the fine structure of absorption spectra under varying temperature and concentration conditions. With this in mind, int>estigations hare been made into the emission and absorption spectra of the K-series of atoms of transition elements in alloys and compounds. In the problem concerned with the electronic structure of high-melting compounds of transition metals, considerable importance is attached to the question of ascertaining the role played by 3d4sp electrons of metal and 2p electrons of metalloid in the formation of chemical bonds and of giving, on the strength of this data, an explanation of the properties which seem to be contradictory at first sight: good conductivity inherent in metals and high brittleness and high-melting characteristics typical of covalent compounds. Over the last few decades this question has attracted the attention of many investigators whose studies were devoted to this type of compound. Many works, both of theoretical1-3 and experimental4- l5 nature , have contributed much to the elucidation of the physical character of the phenomenon referred to. Alongside the investigations in the field of electric resistance, Hall effect, paramagnetic susceptibility, electronic heat capacity, and the temperature of transformation into a superconducting state, we should particularly emphasize the studies on X-ray spectra, which have played a significant role in the development of the zonal theory for high-melting compounds. This fact has become highly evident after the theoretical calculation of the energy spectrum has been made and the density of states curve in Tic, TiN, and Ti0 has been plotted by Ern and Switendick3 who used the method of augmented plane waves. Correlation of the results of the theoretical calculation of the band structure in the compounds listed above with the data obtained by X-ray spectroscopy studies showed that X-ray spectra can be a source of valuable information on the electronic structure of high-melting compounds within a wide range of ener- gies. It is well known that X-ray emission spectra basically give a direct picture of the occupied excited states above the Fermi level of a solid (valence band, conduction band) and that the absorption spectra (region of initial absorption) give a similar picture of states corresponding to the unoccupied levels near the Fermi surface. Full information on the density distribution of electronic states by energies can be obtained by combining the emission and absorption spectra. Such an opportunity arises from investigation

Jan 1, 1970

By Roy D. McLellan

Electrolytic production of cadmium at the Great Falls plant started in the first part of the year 1925. Prior to that time, an experimental unit had been in operation for a few months during the year 1922. At present the plant is the largest producer of cadmium, not only in the United States but in the world. Electrolytic cadmium is characterized by its very low content of impurities. The main impurities, which are lead, copper, zinc and iron, do not aggregate more than 0.05 per cent., leaving a cadmium content better than 99.95 per cent. The consumption of cadmium has increased rapidly since the war, with the growing use in the plating industry. Cadmium plating has come into prominence because of its connection with the automobile and radio industries. As a protective coating, a deposit of cadmium is superior to zinc. Cadmium is also used extensively in alloys. Important among these is the alloy with copper used in telephone and trolley wire. In proportion of 0.5 to 1.2 per cent., cadmium adds materially to the strength and wearing qualities. Practically all commercial zinc concentrates contain a small amount of cadmium. In the electrolytic zinc process, the cadmium that is dissolved in the regular leaching operation is removed from solution with metallic zinc, generally added in the form of zinc dust. This precipitate also contains the copper taken into solution and the excess of zinc dust, which is required in order to insure a complete removal of all impurities. The precipitate is treated by a separate process to recover the copper, cadmium and excess zinc. In order to make the metals more soluble and to render insoluble such impurities as iron, arsenic and antimony, the precipitate is roasted. The roasting is carried out in gas-fired McDougall furnaces, with a roasting temperature of about 700' C. The roasted residue is leached with dilute sulfuric acid, spent electrolyte from the zinc electrolyzing, containing 10 to 12 per cent. free H2S04. The leaching is done in cylindrical tanks of 30 tons capacity, agitated

Jan 1, 1930

By John J. Secretary Egan

The present list of problems relating to the physical chemistry of steelmaking has been prepared by the Committee on the Physical Chemistry of Steelmaking, from answers to a questionnaire submitted to a number of metallurgists engaged in both industrial and educational work throughout the United States. The purpose of the project is to make available to research laboratories a list of problems, all reduced to their simplest terms, the solution of which would aid in creating a better understanding of the steelmaking process. It is not intended to restrict the problems to practical steelmaking. The list also includes the study of the properties, and their correlation, as well as the physical and chemical reactions, of all substances that occur or that may be in any way associated with steelmaking operations, such as metallic substances, refractories, nonmetallic inclusions, and the constituents of slags. Many of the problems can be carried out in university or other research laboratories. Others may be most successfully attacked by cooperation of the research men with the operating personnel. It is the Committee's earnest wish that this cooperation be fostered. It is requested that investigators who are working on any of the problems listed and who anticipate future publication of their results, notify the Secretary of the Committee that such investigation is in progress. Suggested additions to the present list are also requested. The Committee is undertaking to act as a clearing house for information regarding the topics in this field that are being actually studied. Interested persons are invited to correspond with the Secretary. I. Data involved in the state of equilibrium for the various systems (laboratory work, almost entirely). A. Specific heats, heats of formation, entropies and free energies of various PURE ELEMENTS OR COMPOUNDS; ALSO CERTAIN TYPICAL SLAGS AND REFRACTORIES I. Determination of specific heats and entropies of oxides, sulphides, nitrides, etc, over a wide temperature range. 2. Determination of free energies of oxides, sulphides, nitrides, etc., over a wide temperature range. 3. Determination of the heats of formation of the oxides, sulphides, nitrides, etc. 4. Determination of the thermodynamic properties of the more important mineral-ogical constituents of the basic open-hearth slags such as calcium silicates, calcium phosphates, calcium ferrites, manganese silicates, FeO and Fe2O3. 5. Determination of the specific heats of open-hearth slags, including liquid silicates, if possible.

Jan 1, 1941

By John J. Secretary Egan

The present list of problems relating to the physical chemistry of steelmaking has been prepared by the Committee on the Physical Chemistry of Steelmaking, from answers to a questionnaire submitted to a number of metallurgists engaged in both industrial and educational work throughout the United States. The purpose of the project is to make available to research laboratories a list of problems, all reduced to their simplest terms, the solution of which would aid in creating a better understanding of the steelmaking process. It is not intended to restrict the problems to practical steelmaking. The list also includes the study of the properties, and their correlation, as well as the physical and chemical reactions, of all substances that occur or that may be in any way associated with steelmaking operations, such as metallic substances, refractories, nonmetallic inclusions, and the constituents of slags. Many of the problems can be carried out in university or other research laboratories. Others may be most successfully attacked by cooperation of the research men with the operating personnel. It is the Committee's earnest wish that this cooperation be fostered. It is requested that investigators who are working on any of the problems listed and who anticipate future publication of their results, notify the Secretary of the Committee that such investigation is in progress. Suggested additions to the present list are also requested. The Committee is undertaking to act as a clearing house for information regarding the topics in this field that are being actually studied. Interested persons are invited to correspond with the Secretary. I. Data involved in the state of equilibrium for the various systems (laboratory work, almost entirely). A. Specific heats, heats of formation, entropies and free energies of various PURE ELEMENTS OR COMPOUNDS; ALSO CERTAIN TYPICAL SLAGS AND REFRACTORIES I. Determination of specific heats and entropies of oxides, sulphides, nitrides, etc, over a wide temperature range. 2. Determination of free energies of oxides, sulphides, nitrides, etc., over a wide temperature range. 3. Determination of the heats of formation of the oxides, sulphides, nitrides, etc. 4. Determination of the thermodynamic properties of the more important mineral-ogical constituents of the basic open-hearth slags such as calcium silicates, calcium phosphates, calcium ferrites, manganese silicates, FeO and Fe2O3. 5. Determination of the specific heats of open-hearth slags, including liquid silicates, if possible.

Jan 1, 1941

By Frank Clemes Smith

The study of the so-called refractory gold-ores of the Potsdam sandstone, ores which are probably of wider occurrence and of much greater economic importance in the Black Hills than is generally supposed, has led the writer to formulate in the present paper some of the results obtained in the course of a special examination of these particular ores, conducted at the State School of Mines at Rapid City, So. Dak. Various circumstances have interrupted the work, and it will easily be seen that relatively little has yet been accomplished; but it is hoped that this little may be of sufficient interest to justify a later supplement. Tellurium, discovered by Muller von Reichenstein in 1781, is generally classed as a very rare metal; it is further mentioned by one of our late writers as " of comparatively little importance," and as obtained from its ores by a " complicated process.'' Concerning its rarity, we have some trustworthy evidence below. Its commercial importance, particularly in connection with electrical appliances, has been passed upon by Mr. Edison ; * and it is certain that, in some metallurgical processes for the treatment of gold- and silver-ores, it may be saved as a byproduct at a relatively reasonable expense. The importance of tellurium as a mineralizing agent is emphasized by the remarks of one of our leading metallurgists,jwho, in his own practice and by a wide series of experiments, has found its occurrence to be much more general than has been supposed. Recently the same writer has discussed the occurrence of tellurides and oxidized tellurium compounds in the gold-ores of Cripple Creek, Colo., and in those of the Black

Jan 1, 1897

By M. E. Wadsworth, G. W. Warren

INTRODUCTION Hydrometallurgical processes for the extraction of metal values can be divided into two broad categories: (a) Processes involving the treatment of high grade material (e.g. finely divided mineral concentrates); and (b) processes which treat lower grade material (ores, waste dumps, etc.). This discussion will be directed primarily toward the first category, but in either case a fundamental knowledge of the intrinsic kinetics and thermodynamics is necessary to understand the behavior of the system. The bulk of research efforts in the last decade along these lines has been aimed at the recovery of copper (1-8). However much information has also been reported on uranium (9, 10) , zinc (11) , cobalt and nickel (12, 13). More comprehensive reviews on these areas are also available (14). As discussed by Sepulveda and Herbst (15, 16) one of the most difficult problems facing process designers is the acquisition and scale-up of reliable information concerning the intrinsic kinetics of leaching systems. The scale-up or modeling of these multiparticle systems is far more complex than that of homogeneous ones. This is due to the numerous rate determining steps which are possible with heterogeneous reactions and the broad distribution of properties of a multiparticle feed such as particle size and mineralogical composition (16). In addition, other factors must also be considered such as interactions between particles, the anisotropic nature of individual particles, the effect of solution chemistry, and electrochemical phenomena. All of these factors must be taken into account, often simultaneously. The thrust of this paper will be to more closely examine how the factors mentioned above can be treated. Some elementary examples of

Jan 1, 1980