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By Lester Guttman

The connection between short-range order and thermodynamic activities in binary solid solutions has been pointed out by Birchenall1 who calculated approximate values of the energy of interaction of Zn and Cu and of the degree of short-range order in alpha-brass at one composition and two temperatures. The purpose of this note is to call attention to a somewhat more accurate theory than that used by Birchenall and to extend the calculations to a wider range of temperatures and compositions as a means of testing its applicability. This is an example of the well-known general method of comparing measured thermodynamic functions of a system with those calculated from a microscopic model by means of statistical mechanics. In this case, mathematical approximations must be used which make difficult any decision about the validity of the model. Birchenall's statistical method resembles closely that calletl by Fowler and Guggenheim2 the "quasi-chemical" method which has been shown to lead in certain cases to results identical with those obtained by the method of Bethe.3 The quasi-chemical method has been extended by Takagi4 to give general formulas for the free energy of binary solid solutions based on several lattices at all compositions and temperatures. Specifically, he treats the four systems typified by: I. ß—brass; 2. a— brass; 3. AuCus; 4. AuCu. When the temperature is so high that no long-range order exists, these formulas reduce to the same form for all lattice types, namely: F - FO = (E - EO) - T(S - S°) = ½N(c — x)(2vAB — vAa - Vbb) + M1/2KTzN[x log x + 2(c - x) log (c - X) + (I - 26 + X) log (1 - 2c + x)] -kT(z - I)N[c log c+(I-c) log (I -c)] Eq 1 Here the symbols have the following meanings: F—Helmholtz free energy E—nergy 5—ntropy k—the gas constant per molecule z—coordination number, (e.g. I2 in a-brass). N—total number of atoms c—atomic fraction of A Vaa, vbb, vab—nergy per bond of the corresponding bonds log means log, throughout The superscript ° denotes the thermodynamic fuliction in the standard state, which has been chosen to be pure A or B with the same crystal structure as the solid solution. The quantity x is the ratio of the number of A-A bonds to the total number and for minimum F satisfies the equilibrium condition Vaa + Vbb — 2Vab _ (c — x)2 kT l0g x(i - 2C + x The free energy may also be written in terms of /La and B, the chemical potentials or partial free energies per alom:

Jan 1, 1949

By Miroslaw Hajdasinski

Estimation of the economic effectiveness of industrial development projects including mining ones is generally made on the basis of the discrete model of the value changes in time, although the character of these changes is similar to the continuous model. In this paper an attempt has been undertaken to investigate the problem of the value equivalence of both models exemplified by a construction of an underground coal mine. An effort has been made to determine the errors which for different estimation criteria appear in result of the application of the discrete model. Theoretical considerations have been supplemented with practical conclusions.

Jan 1, 1977

By H. R. Peiffer

Recently artin has indicated that the recovery of resistivity at 145°C following elongation of molybdenum at room temperature was the result of the annihilation of vacancies. The activation energy for this process was, according to Martin, 1.26 ev. This energy seems to be a reasonable one for the activation energy for the diffusion of vacancies in molybdenum. However, impurity atoms such as carbon, nitrogen, and oxygen4 have an activation energy for diffusion in molybdenum of the same order of magnitude (i.e., 1.45, 1.15, and 2.09 ev, respectively). Cottrell and Churchman have already correlated the return of impurity atoms to dislocations in cold-worked iron with the return of the upper and lower yield point. According to cottrel16 the diffusion of carbon atoms to dislocations results in the return of the yield point. As the carbon atoms become trapped by dislocations, Bhatia has shown that a decrease in the electrical resistivity is to be expected. Cottrell and Churchman were able to correlate experimentally the decrease in electrical resistivity with the return of the yield point. Since one would expect strain aging to occur in molybdenum, an experiment was performed to determine whether the resistivity recovery at 150°C for molybdenum cold-worked at room temperature can be correlated with the return of an upper and lower yield point. For this experiment 3/16-in. tensile bars of Climax molybdenum, 99.961 pct pure, were used. The specimens were annealed at 1000° C for 1 hr in an argon atmosphere and then were elongated up to 10 pct on a Baldwin-Lima-Hamilton FGT

Jan 1, 1959

By H. H. Uhlig

In our study of the mechanism of and the prevention of corrosion in stainless steels, it was considered of fundamental importance to obtain knowledge of the surface structure of such alloys. If corrosion resistance is due to a self-healing oxide layer, which like a paint film protects the underlying metal, it would be obviously relevant were the effort made to make the film less permeable and more adherent; for example, the surface might be expected to respond to an anodizing process, which is found successful in increasing the film thickness and corrosion resistance of aluminum. However, if passivity and corrosion resistance of stainless steels are due to another cause, the attack of the problem would follow another path. One of the most effective techniques for studying passivity and corrosion tendency is the measurement of the electrochemical potential. Not only can one determine by potential measurements whether a metal is active or passive, but also one can determine the degree of passivity and rate of transformation of passivity with time. Chemical media that build up or destroy passivity when in contact with the steel can also be classified by potential measurements. Something can be learned, too, of the effect of alloy additions such as molybdenum to 18-8, known to decrease corrosion of the alloy in chloride solutions. A study of alloys in previous investigations has sometimes included data on the electrochemical potentials. Tammann and Sotterl measured the electrochenlical potentials of alloys of iron-molybdenum and iron-chromium and reperted the critical concentration of molybdenum or chromium at which passivity initiates. Strauss2 made similar measurements for the iron-chromium system. The electrochemical potential3 has also been used to indicate carbide precipitated 18-8. In 18-8, heat-treated to precipitate carbide, active metal exists at the region of the grain boundaries, contrasted with passive metal within the grains, the active metal accounting for a resultant active potential. Several

Jan 1, 1940

By H. H. Uhlig

In our study of the mechanism of and the prevention of corrosion in stainless steels, it was considered of fundamental importance to obtain knowledge of the surface structure of such alloys. If corrosion resistance is due to a self-healing oxide layer, which like a paint film protects the underlying metal, it would be obviously relevant were the effort made to make the film less permeable and more adherent; for example, the surface might be expected to respond to an anodizing process, which is found successful in increasing the film thickness and corrosion resistance of aluminum. However, if passivity and corrosion resistance of stainless steels are due to another cause, the attack of the problem would follow another path. One of the most effective techniques for studying passivity and corrosion tendency is the measurement of the electrochemical potential. Not only can one determine by potential measurements whether a metal is active or passive, but also one can determine the degree of passivity and rate of transformation of passivity with time. Chemical media that build up or destroy passivity when in contact with the steel can also be classified by potential measurements. Something can be learned, too, of the effect of alloy additions such as molybdenum to 18-8, known to decrease corrosion of the alloy in chloride solutions. A study of alloys in previous investigations has sometimes included data on the electrochemical potentials. Tammann and Sotterl measured the electrochenlical potentials of alloys of iron-molybdenum and iron-chromium and reperted the critical concentration of molybdenum or chromium at which passivity initiates. Strauss2 made similar measurements for the iron-chromium system. The electrochemical potential3 has also been used to indicate carbide precipitated 18-8. In 18-8, heat-treated to precipitate carbide, active metal exists at the region of the grain boundaries, contrasted with passive metal within the grains, the active metal accounting for a resultant active potential. Several

Jan 1, 1940

By J. C. Williams, M. J. Blackburn

MANY aspects of the formation of the metastable w phase in titanium-transition metal alloys have been described in several recent papers.1-4 These papers have reviewed earlier work on the w phase and have further defined most of the important features related to the formation of this phase, e.g-., its crystal structure, composition, and morphology. There are, however, several important points regarding formation of the w phase in titanium alloys which have been described in less detail. Two of these are the relationship between lattice misfit and w phase morphology and the influence of lattice misfit on the mode of formation of the equilibrium a phase. In this communi- cation we will present transmission electron microscopy results relevant to these two points. The alloys used in this study were prepared by non-consumable electrode arc melting, each 30-g button being remelted a minimum of twelve times. The alloy compositions we have studied are listed in Table I. Thin foils were prepared using standard techniques described elsewhere. Two distinct c' phase morphologies have been reported in earlier papers. The phase is ellipsoidal in the Ti-Mo3 and Ti-Nbl system and cubical in the Ti-V3 system. Results of the present study show that the w phase is also cubical in Ti-Mn, Ti-Fe, and Ti-Cr alloys as illustrated in Fig. l(b) to (d). Fig. l(a) shows the ellipsoidal morphology in Ti-MO3 for comparison purposes. It was suggested in an earlier paper3 that the w phase morphology may be controlled by the lat-

Jan 1, 1970

By H. De Cizancourt

Jan 1, 1939

By H. De Cizancourt

Jan 1, 1939

Jan 1, 1949

By T. Egleston

SOME months ago samples of black oxide of copper and of pig copper from Colorado were sent to me to examine for arsenic and

Jan 1, 1882

By R. E. Hobart

THE development of the Hauto power plant and the claims made by various engineers that electricity was more economical than steam for power purposes in and about the mines; led the Lehigh Coal and Navigation Co., in 1911, to conduct a test to ascertain the consumption of power used by a large steam hoisting engine. The question being one on which no reliable information could be found, and the opinion of various engineers differing to such an extent, it was decided that a test under actual operating conditions was necessary. This was arranged for at one of the collieries. The engine selected was a 30 by 60-in. (76.2 by 152.4-cm.) piston-valve engine of modern type, and comparatively new. The boiler plant from which the hoist received its power was about 600 ft. (182 m.) from the engine, the latter being fed by a 10-in. (25.4-cm.) steam line insulated with magnesia pipe covering. Two batteries of the boiler plant, aggregating 1200 hp., were cut off and fed into a separate steam line leading direct to the hoist engine. Steam auxiliaries, consisting of feed-water pump and blowers, were fed by the boilers in test, and their consumption charged against the hoist. A barrel weighing device was installed, as it was felt that this would be the most accurate way of determining the consumption of water. The fuel, No. 3 buckwheat, was carefully weighed, and every precaution was taken to make the test accurate in every particular. The test was run for 1 week, or a total of 168 hr. A record was kept of the number of trips hoisted or lowered, and continuous indicator cards were taken. One particular set of cards was taken with the hoist operating balanced, and also with the hoist operating with no counterweight other than the empty cage, the coal in the car being weighed. The speed of the hoist was taken by means, of a graphic recording instrument which registered the number of revolutions every 5 sec. From this record, speed-time curves were plotted.

Jan 2, 1918

By Harrison R. Cooper

This section will outline procedural, statistical, and model applications developed for specific problem solving and for specific applications in beneficiation processes. Iron Ore Processing Introduction of taconite as a basic raw material in the iron ore industry took place with application of high order technical resources for process development and engineering. This investment of resources encouraged computer utilization to maximize efficient use of capital. From this recognition, process control computers have been installed for operations use in the major taconite plants of the iron range. One of these installations, the Minntac Division of U. S. Steel at Mountain Iron, Minnesota, is described in the paper by Chase in these proceedings. Other computer techniques used in taconite processing are outlined by Tuttle, Ahlquist and Carlson, representing Erie Mining. In this volume Tuttle, et al. describe statistical methods for development of information in taconite beneficiation. Statistical methods used in iron ore processing are described by Volin in treating flotation data as outlined in prior proceedings of the symposia and in other publications. 1,2,3 Industrial Minerals The use of linear programming for feed blending at the Carlsbad operation of International Minerals and Chemicals was outlined by Nunnekoven in 1963.4 Subsequent application of this procedure at the Kingston phosphate operation in Florida was described by Loper. Continued development led to installation of an on-line computer in the Kingston plant which reached operational status in 1967.6,7,8 Application of an on-line computer to industrial mineral production accomplished at Kingston is regarded as a milestone in computer use development. Following this achievement, the Cominco potash beneficiation plant near Saskastoon in Canada was automated by installation of an on- line computer programmed to carry out direct digital control functions to effectively operate the plant by process computer. The procedures used in the Cominco operation are described by Madge in this volume. Development of a mathematical model

Jan 1, 1969

By Jack Fox

Three years ago we attended the V International Mining Congress in Moscow. This year we attended the VI International Mining Congress in Madrid. By almost any criterion, this was a most successful convention. There were 1717 registrants, not counting the ladies. I don't know how many of the latter there were, but they certainly made a welcome addition to the group. Once again, the International Organizing Committee put together a very impressive technical program which the Spanish National Committee backed up with a brand new Palacio de Congresos admirably equipped with simultaneous translation devices and an organization that provided an excellent social program, a tremendous set of post- meeting excursions, and very impressive opening ceremonies, entertainment and closing ceremonies. There was also an exhibit on the subject of Spanish and Spanish American mining history in the Palacio de Congresos.

Jan 1, 1970

By Ian W. Wark, Keith L. Sutherland

IT has been shown' that in the absence of heavy metal salts, the nature of the alkali used to promote differential flotation-whether caustic soda, lime or sodium carbonate-is unimportant. The hydroxyl ion is the active depressant upon which differentiation depends, and the pH value determines whether a film of collector forms on any given mineral surface. Even when sodium cyanide is used in conjunction with alkalies, it is the pH value and not the nature of the alkali or its concentration that is important, for upon the pH value alone depends the fraction of the added sodium cyanide that is present as cyanide ion, which is the true depressant. When heavy metal salts become dissolved from partly oxidized ores, or are added intentionally as activators, conditions are different, and metallurgists have found that lime and sodium carbonate do not give identical results, even when added in amounts sufficient to produce the same pH value. In the few instances in which we had attempted to confirm this view, we had failed to do so, for, with nothing to guide us, we had inadvertently chosen solutions that gave contact curves of a "standard type," which correspond to conditions of ready floatability. Now, however, we find that, in the presence of copper salts, and within a restricted range of reagent concentrations, the nature of the anions present is important, and that sodium carbonate does influence the results, apart from the usual effect due to its influence on pH value. With the recognition of this anion effect, and with the control of temperature already introduced,2 it appears that the factors of major importance in connection with this set of reagents have been taken into consideration, and that the results obtained and the conclusions drawn from contact tests will be of more immediate value to the operator. It is not difficult to suggest an explanation for the influence of the carbonate ion in the presence of copper sulphate. The works of Picker-

Jan 1, 1939

By T. J. Whalen, S. M. Kaufman

Surface-tension measurements for liquid Fe-C-Co and Fe-C-Ni alloys were performed by the sesszle-drop technique at 1350o and 1425°C. Cobalt was shown to he more effective than nickel in lowering the surface tension of Fe-C alloys A minimum value for surface tension of 1640 dynes per cm was found in the Fe-C-Co system at a concentration of 1.5 pet C and 12pet Co. Analysis of these measurements in terms of adsorption and desorption behavior indicated that cobalt and nickel lower surface tension in Fe-C alloys by replacing carbon at the liquid-vapor interface. Comparison of results to date for Fe-C liquid alloys has shown that most substitutional-type elements having about the same atomic diameter as iron also have relatively the same influence on surface tension when present in dilute amounts. It has been shown previously that surface-adsorption behavior in liquid Fe-C ternary alloys is related to the manner in which the ternary addition affects the activity of carbon in the bulk solution.' Certain ternary additions, such as chromium, tending to decrease carbon activity cause adsorption of carbon and chromium to the liquid-vapor interface. Additions, such as silicon, increase the carbon activity, resulting in a desorption of carbon and an adsorption of silicon. Both cases were shown to cause a decrease in surface tension due to adsorption. It is the object of this paper, as part of the writers' continuing interest in the effect of alloying additions on the surface tension of Fe-C alloys, to present and discuss surface-tension data on solutions in the ternary systems Fe-C-Co and Fe-C-Ni. Available activity measurements for these systems in the solid state indicate a strong increase in carbon activity when either nickel or cobalt is added to Fe-C alloys.2, 3 EXPERIMENTAL PROCEDURE The alloy compositions used are shown in Table I. These alloys were prepared by vacuum melting in stabilized zirconia crucibles and then vacuum casting into cold-steel molds. The nominal analyses for the alloys used in this investigation are given in Table I. Surface tensions and densities were measured by the sessile-drop method4,5 in conjunction with the tables of Bashforth and bdams.' Specimens were prepared by slicing 1/4-in. cubes from the center of the vacuum-cast ingots and grinding the edges of these cubes until their shapes approximated spheres with flat bottoms. Proper handling techniques, including an acetone rinse immediately before use, assured minimum contamination from sources extraneous to the actual melting. For each experimental run a sample was placed on a BeO plaque and positioned and leveled inside a vacuum induction heating apparatus. The sample and plaque arrangement sat inside a molybdenum tube which acted as the susceptor. Diagrams of this apparatus may be found in the literature.= After heating to temperatures just above the liquidus at pressures of the order of 10-4 to 10- 5 mm Hg, photographs of the drop profile were made using its natural thermal radiation as a light source. Some measurements were made with partial pressures (-1 cm Hg) of a mixture of H2 and He gases. The H2-He atmospheres proved to be necessary at higher nickel contents to retard excessive vaporization losses. Chemical analysis for carbon and the ternary addition was performed for each alloy sample after completion of the experimental run.

Jan 1, 1964

By N. J. Grant, Hans Brunner

ThE materials used in this investigation were furnished by the Aluminum Co. of America and consisted of high-purity alurhinum (99.995 pct) and two aluminum-magnesium alloys containing approximately 2 and 5 pct Mg. The compositions of these alloys are listed in Table I. The materials were received as hot rolled 3/8-in. diam rods and were made from the same heats as the materials which were previously used in this laboratory.'j3 The rods were cold swaged to 1/4-in. diam by 1 in. long, and then had two parallel flats machined over the gage length 0.085 in. apart. The test bars were annealed for 10 min at 700° F, and strained 1 pct in tension at room temperature. They were electropolished (80 pct acetic acid; 20 pct perchloric acid, 70 pct concentration) at a temperature of 60°F at approximately 20 v. A grid, transverse or square, spaced 0.2 mm apart, was impressed by rolling a fine threaded screw (128 threads per in.) across the flat surfaces. The depth of the grooves was less than 5 p. For final annealing and grain size control the specimens were enclosed in aluminum foil and sealed in Vycor tubes. Annealing conditions varied from 1 hr at 700° F to 5 days at 1050° F, depending on the alloy content, to give for most of the specimens a final grain size of about 1 mm. This treatment was followed by electropol-ishing as described above. For the test series presented in Figs. 4 and 5 round specimens were used instead of flat ones, and fine machining marks served as marker lines instead of the impressed grid lines. Electropolishing was omitted. The major advantage is that the spacing of the machining marks is only about 1 u as compared to the 200 u of the impressed grid lines, permitting higher precision in strain measurements. Unfortunately the strain annealing necessary for grain size control also resulted in some preferred orientation of the grains. The preferred orientation of three arbitrary specimens was measured by X-ray diffraction methods and the averaged results are shown in Fig. 1. The possible effects of the preferred orientation on the test results will be discussed later. The testing temperatures were 410°, 515", 725", and 940° F, with one exception in the case of the 5.1 pct Mg alloy. Since the solubility limit of this alloy is 520°F, a test temperature of 545°F was cho-se sen instead of 515°F. The selection of the test temperature was based on two considerations: 1) at 900°F and above, extensive grain boundary migration made it more difficult to measure grain boundary sliding; 2) at 400°F and below, there was so little grain boundary sliding that it was again difficult to make precise measurements. The stress was chosen to give a creep rate of approximately 2.7 pct per hr in connection with Figs. 2

Jan 1, 1961

By Elmer W. Pehrson

THE founding of the American Institute of Mining Engineers in 1871 came at an unusually significant moment in the life of our country. The industrial revolution, in which mineral production played a major role, was just getting underway. The iron industry, established several decades earlier, was reaching sizable proportions. In 1871 pig-iron production was approaching 2 million tons, and the industry had spread as far west as Missouri and Wisconsin. The chief sources of iron ore were Pennsylvania, New Jersey, New York, and Michigan. The age of steel was in its infancy; production had not yet reached 100,000 tons per annum. The gold rush to California two decades earlier and the discovery of other gold and silver bonanzas in the West paved the way for the transcontinental railways, which were then being built and which contributed much to the subsequent development of the great copper, lead, and zinc districts of the Rocky Mountain area. Regular production of copper in the Michigan peninsula and of lead in Missouri and the upper Mississippi region had been established for many years but on a scale dwarfed by the quantities later required as technical progress, invention and enterprise made possible the rapid expansion of industry. Discovery of oil in Pennsylvania in 1859, the growing recognition of the

Jan 1, 1947

By V. H. Wilhelm

The year 1936 was a prosperous one for the oil industry in California. Increases in crude prices were posted in February and March. Re-establishment of voluntary curtailment in February was a factor in holding production at an efficient level throughout the year. Reduction of storage was effected through adherence to curtailment measures, aided by greater demand and smaller average well completions. During the first six years of voluntary curtailment, allotments were increased during the summer season and reduced during the winter season. This year, good results were obtained through a revised system of allocation, by which the California monthly quota was held constant at approximately 540,000 bbl. per day. After a 7-month period of practically unrestricted production (ending in January 1936), numerous operators found that curtailment was still necessary, as California and export market,s were not yet capable of absorbing the state's potential production, which was estimated to be in the neighborhood of 850,000 bbl. per day. Therefore, in February California operators again placed themselves under voluntary curtailment; with the result that state production dropped from around 700,000 bbl. per day in January to a low of 565,000 bbl. per day in April, and increased gradually to around 585,000 bbl. per day for December. Drilling activity during the year increased about 10 per cent over that of the preceding year, although the resultant production per well decreased. Field Discoveries As a result of a very active wildcatting campaign in California, aided by better interpretation of geophysical data, five new oil fields and two new gas fields were discovered. Oil Fields Greeley Field, Kern County.—The Standard Oil Co. added to its list of djscoveries by drilling and completing its K.C.L. No. 11-1 well at a

Jan 1, 1937

By S. E. Bretherton

Discussion of the paper of S. E. BRETHERTON, presented at. the San Francisco meeting, September, 1915, and printed in Bulletin No. 104, August, 1915, pp. 1595 to1599. ANTON EILERS, Brooklyn, N. Y. (communication to the Secretary*). While the advantages in the use of high-line siliceous slags in lead smelting which Mr. Bretherton discusses in this paper are obvious under certain economical conditions, he gives me credit for the introduction of such slags when it does not belong to me. It is true I did considerable experimental work, off and on, for the purpose of finding such slags, while at the Germania in 1877 and 1878, but I did not have occasion to introduce any such slags for regular work, because I had no ores which fitted the economical conditions for using high silica and high lime, except in isolated cases for very brief periods. On the contrary, the ores I had to treat were mostly very ferruginous and very low in silica, so that, economically, I was compelled to run nearly always on slags, which allowed me to use the abundant flux I had without cost. It was August Raht who first had occasion to establish and use for long periods a slag high in silica and line, and low in iron. This was when he was confronted with the task of smelting the. Horn-Silver ores at the smelting works at Franklin, Utah, with as little expenditure for fluxing material as possible. I was at that time in Leadville, Col., where, in the new works I had built, the Billings and Eilers smelters, I had occasion to use profitably many slags, but never anything as high in the earthy bases and in silica as Mr. Raht had to use.

Jan 12, 1915

By W. C. Kelly, E. J. Essene, A. M. Affifi

Occurrences and associations of natural tellurides are constrained by the relative fugacities of Te, in specific mineralizing environments. Some are rare (e.g., FeTe2) and others absent (e.g. MoTe , ZnTe) m nature because high f-Te2/f-S2 ratios are rare or unattainable , whereas others (e. g . , Ag2Te,HgTe) require lower ratios and are common. Complex and seemingly chaotic sulfide-telluride associations are, in fact, highly systematic and depend both on temperature and fugacity ratios. Some older sulfides act as buffers via reactions such as PbS + Te2 = PbTe + S2, thereby affecting the deposition and paragenesis of younger tellurides and the combined or uncombined mode of occurrence of precious metals. Thermochemical calculations of telluride-sulfide-oxide equilibria can have pragmatic value. The thermochemical approach tells us little about the Te "source", but is beginning to unravel the systematics of telluride mineralogy and controls at the precipitational end of the line.

Jan 1, 1985