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By L. S. Darken, H. A. Wriedt

The equilibria at 1 atm total pressure and 600° to 1300°C (1112° to 2372°F) between gas mixtures with various partial pressures of the reactive constituents (principally sulfur dioxide, carbon dioxide, water vapor, oxygen or carbon monoxide, and hydrogen) and coexisting solid phases (groups variously including calcium oxide, calcium carbonate, calcium sulfide, calcium sulfate, iron, ferrous sulfide, and the iron oxides) are examined. Tables and charts show the combinations of temperature, oxygen activity, and carbon dioxide partial pressure under which the various groups of the solid phases coexist and the corresponding sulfur dioxide pressures. In the presence of calcium sulfide, calcium sulfate, and calcium oxide, the partial pressure of sulfur dioxide has a peak value at each temperature which increases from 101 atm at about 800°C (1472°F) to 1 atm at about 1200°C (2192°F). With water vapor present, hydrogen sulfide may predominate among gaseous sulfur compounds, particularly at low temperatures and oxygen activities; under all other circumstances considered, sulfur dioxide is the dominant gaseous sulfur-bearing species.

Jan 1, 1974

The pressure of the gas in equilibrium with sphalerite has been determined in the temperature range of 680' to 825°C, using the Knudsen orifice method. A comparison of these experimental pressures with those calculated from thermal data and from other equilibrium measurements shows that the vapor above sphalerite is predominantly dissociated ZnS. Equations have been given for correctly calculating dissociation pressures using the Knudsen orifice method. It has been shown that the experimentally determined pressure is the same, whether the zinc sulphide is sphalerite or not, or a mixture of wurtzite and sphalerite. CONFLICTING points of view appear in the literature on the constitution of the vapor in equilibrium with solid zinc sulphide in the vicinity of 800°C. By comparing the dissociation pressure calculated from thermodynamic data and the vapor-pressure determination of ZnS by Veselovski,1 Lumsden2 has concluded that the vapor consists largely of dissociated ZnS. Sen Gupta,' however, concludes from his spectroscopic determinations that the vapor is largely ZnS molecules. In view of the fact that the thermodynamically calculated' dissociation pressure is higher than that experimentally measured by Veselovski, it seemed in order to repeat Veselovski's measurements. Experimental Procedure The method used for the determination of the pressures in this papel- is the Knudsen effusion cell. The apparatus and procedure were described in a previous paper- from this laboratory on the determination of the vapor pressure of silver. The only difference is that the Knudsen cell in this work is made from platinum and there is no external cover around the cell. The cell is an ordinary platinum crucible of 2.2 cm top diameter with a capsule cover. It was thought that platinum might stand up at these temperatures to the solid and gaseous ZnS, since it was found that the weight of the platinum cell itself did not change appreciably on heating ZnS in it at the working temperatures. To insure that reaction of the zinc sulphide with the cell was not giving' a false value, a stabilized zirconia cell was employed for check runs. Fig. 1 shows the comparison, which is satisfactory. Veselovski previously had measured the vapor pressure of ZnS using a silica Knudsen effusion cell. On repeating his experiment in this laboratory, it was found that ZnS at-tacked the silica cell, giving it a marked frosty appearance. This led to the belief that Veselovski's result:; may be in error. Also, he was operating at pressures above the range ordinarily considered safe for the Knudsen method. The effusion rate was measured by weighing the cell before and after each run. The weight loss during heating to temperature and cooling down was measured and subtracted from the weight loss during the actual run. The zinc sulphide used in this investigation was from two sources: Fisher cp grade, and a sample of pure sphalerite supplied by Mr. E. A. Anderson of the New Jersey Zinc Co. Before and after the series of runs with Fisher ZnS, X-ray analysis showed that both wurtzite and sphalerite were present. However, the ratio of sphalerite to wurtzite increased. All measurements were made below the transition temperature which has been reported" to be 1020°C. The data obtained in this investigation are tabulated in Table I. The pressure was calculated by the usual Knudsen formula" on the assumption that ZnS molecules were effusing. From these data, using pure sphalerite in the platinum Knudsen cell, the vapor pressure of ZnS, in mm of Hg, as a function of temperature is given by the solid line in Fig. 1. The best straight line, as determined by the method of least squares, is given by 14405 logpzns =-14405/T +11.032. A comparison of these results with Veselovski's shows that his results are about 50 pct lower. Discussion The vapor in equilibrium with solid zinc sulphide in the temperature range of this study will consist of Zn, S2, and ZnS mol, since other species of zinc and sulphur' are relatively unstable. The question to be settled is whether or not ZnS is largely dissociated. The derivation8 which follows gives the method of calculating the pressure of zinc and sulphur over solid ZnS, assuming complete dissociation, from Knudsen cell data. The free energy of the reaction 2 ZnS(solid) ? 2 Zn(gas) + S2(gas) is given by ?F?° = -RT In K = —RT In p12p2 where p1 is the zinc pressure and p is the sulphur pressure. If dissociation occurs in a closed system,

Jan 1, 1955

By B. S. Butler

STUDY of the ore deposits of Colorado has disclosed, in numerous places, sharp changes in both mineralogy and metal content of the primary or hypogene deposits with change in depth. A clear understanding of the meaning of these changes is requisite to form intelligent conclusions that can be applied in the exploration of such ore deposits. This paper is an attempt to set forth some of the geologic and chemical relations of minerals that bear on this problem. The effect of the differing electrode potentials of elements on the order of oxidation and on the order of displacement of one metal by another metal in supergene sulfide deposits has been studied for many years by several investigators. The results all agree rather closely with the original Schürmann series of replacability of metal sulfides, as Wells has shown.1 So far as the writers are aware there has been little attempt from the geologist's viewpoint to correlate the electrode potentials of the elements, other than those of the common metals, with the positions and mode of combination of the elements as found in ore deposits, and in particular in hypogene deposits. Wells' discusses electrochemical activity between solutions and certain ore minerals and mentions the possibility of its effect in precipitation reactions. The senior writer for a number of years has emphasized the importance of oxidation-reduction reactions as a factor in the formation of certain hypogene ore minerals, and as the electrode potentials are a measure of the relative oxidizing and reducing power of the elements and their ions, it seems possible that a study of them may offer some suggestions on certain problems. The data at present available for such a line of attack on oxidation-reduction reactions are too far from complete to offer much help, nevertheless the table of standard electrode potentials

Jan 1, 1929

By Atmaram H. Soni

A statistical study of machinability led the writer to examine existing data in regard to a thermal conductivity-mechanical properties relationship. Various functional relationships were proposed and the multiple correlation determined by statistical methods discussed in detail in the 1iterature.4 The relationship having the greatest engineering and statistical significance is discussed below. The data for cast and wrought aluminum alloys''2 have been compiled and analyzed separately. The results of these analyses are presented in Table I. The empirical equations for estimating the thermal conductivity (cal sec-' cm-I °C) are: for cast aluminum alloys K = 0.584 -0.00984/ -0.00263 Hb [1] and for wrought aluminum alloys K = 0.604 -0.00424l- 0.00170 Hb [2] where 1 and Hb are the percentage elongation and Brinell hardness number. Results of a similar analysis pertaining to stainless steel3 are also given in Table I. This empirical equation for estimating thermal conductivity (Btu per sq ft per hr per °F per in.) is K = 216.19- 1.716l - 0.0997 Hb [3] The relationship between electrical resistivity and mechanical properties was also examined for aluminum alloys using the same statistical method. These results are listed in Table II. While the situation of exact multiple correlation

Jan 1, 1965

By E. W. Steele

In the copper-casting department of a modern electrolytic copper refinery there are two kinds of casting furnaces: the anode, for casting crude copper into anodes for electrolysis; the refined-copper, for casting the cathodes resulting from electrolysis into market shapes, such as ingots, wire bars, and cakes. Both furnaces are reverberatories of practically the same general design and are operated intermittently, putting through a charge normally in 24 hr. The treatment of the copper in the two furnaces is similar, in that oxidation followed by skimming and reduction (poling) is carried on in both; but in the refined-copper furnace, the work must be done with greater care and it is of extreme importance that not the slightest trace of impurity be introduced into the copper. The furnaces usually hold from 150 to 300 tons of molten copper, which constitutes the daily charge. Except in the case of furnaces in the Lake district, where the concentrates from native-copper ores are charged through the roof, the furnaces are charged through the side doors by charging machines similar to those used in open-hearth steel practice. In 1916, at the Perth Amboy plant, of the American Smelting & Refining Co., located at Maurer, N. J., a study was made of the possibility of firing the copper refinery furnaces with pulverized coal instead of by hand. The proposed method possessed obvious advantages over hand firing and coal was a much cheaper fuel than oil at that time. However, there were several objections to its use, the principal ones being the possibility of increasing the sulfur content of the refined copper and the additional slag that might be produced from the ash. The increase of the sulfur content of the refined copper was the more serious, as more than 0.002 per cent. sulfur is objectionable. Any increase of the slag would be expensive as the copper in this slag would have to pass again through the entire smelting and refining process. It was thought that certain modifications in operations and furnace conditions, which will be described later, would overcome these objections SO the proposition was discussed with a manufacturer of coal-pulverizing equipment. He was uncertain concerning the use of pulverized coal

Jan 1, 1925

By Finn Ouchterlony

A simple bilinear R-curve description of crack extension resistance is applied to the testing of sub-size rock core specimens. The K-curve consists of a linear sub-critical part and a flat post-critical part. Formulas for the apparent energy rate resistance quantities Gm, Jm, and [R] are developed. Experiments on notched cores of Ekeberg marble, Bohus granite, and Stripa granite are compared with these predictions. The R-curve model gives reasonable results for Gm -data but fails essentially to describe the Jm and [R]-data. Another model with a sharply increasing linear post-critical part could possibly account for the [R]-data, but direct R-curve measurements seem a better approach.

Jan 1, 1982

By Thomas M. Drown

At the meeting of the Istitote in New York, in February, 1880," I described a process of determining sulphur iu metallic allphides, with especial reference to the determination of pyrites in coal. The procem, as then described, is as follows: A solution of sodium hydrate, of 1.25 specific gravity, is saturated with bromine. If an excess of bromiue is used it must be neutralized by the addition of a little more sodium hydrate. The pulverized mineral or coal is moistened with 25 c.e. of this solution autl heated, then hydrochloric acid is added cautiously to just acid reaction. This operation is repeated with another 25 c.c. of the alkaline solution, and again rendered acid. The mixture should be kept hot. The contents of the beaker or dish are then

Jan 1, 1881

By D. R. Miller

The use of fully grouted cables for ground reinforcement in underground mining is becoming widespread. Reinforcement design for this application has tended to be empirical although some two- dimensional design techniques have been developed. This paper describes a technique based on a model of the behaviour of cables placed across planes moving in shear. The model is three- dimensional and includes a simple model of the 'dowel' effect which arises from the bending of the cables. The model determines the shear resistance developed at a particular shear displacement assuming joint friction and cable parameters. Using data for twin 15.2mm dim. steel strand cables, and a concept of reinforcement efficiency, the application of the model to design wall support in open stopes is demonstrated. The examples consider the cases where major planar structures are known in location and orientation and where, as is more common is open stope development, mapping has indicated that a distribution of potential shear failure structures may be present. The actual location and orientation of potential shear planes is not known. These two cases highlight the underdesign of reinforcement that may arise if the distribution of orientation of potential shear planes is not considered.

Jan 1, 1984

By Cleveland Dodge

THE present organization of Copper Queen employ-ees, known as the Employees' Conference Com-mittee, is really an outgrowth of the former Grievance Committee, which, in turn, had developed from the original Hospital Committee. The relatively small membership of these older organizations, the practical limitation of their activities to the presenting of grievances, and their lack of initiating powers, were the principal defects which the plan now in operation seeks to overcome. A somewhat parallel scheme was instituted in our Sacramento Hill division about four years ago; this gradually developed into the Ways and Means Committee, which, in addition to providing a forum for the discussion of operating problems, was instrumental in establishing an excellent and mutually satisfactory bonus system. Before recommending adoption of the plan now in force, we made extensive inquiries among those who have had any experience in such matters, and ended by proposing a modification of a scheme developed by John Leitch,1 which was characterized by its similarity to the constitution of the Federal Government. As finally remodeled, the. plan was submitted to vote of the entire working forces at the Copper Queen mines, and was adopted by them in May, 1920. Mining opera-tions since that date have been so interrupted that it is scarcely possible to state exactly what the results have been. The following quotations are from a printed pamphlet containing the constitution of the organization, as finally adopted. The first extract is from a letter addressed by the management to the employees: The plan submitted for your approval and adoption is modeled after the constitution of our own country, under which every individual is given an opportunity for advancement, according to his ability and determination, and every citizen is given a voice in the laws that shall govern him. So it is to encourage the individual employee in advancement, and to give him a voice in making the rules that shall govern his conduct, that we favor the adoption of the proposed constitution.

Jan 1, 1923

By W. A. Clark

THE production of sand in an oil well increases operating costs because of abnormal wear in subsurface equipment, the necessity for frequent cleanouts, and the need for a means of disposing of the sand. Moreover, removal of sand from the zone can bring about the creation of cavities from which bodies of formation, sand or shale, may slough into the hole, endangering the shutoff, impeding production or collapsing the liner. The procedure known as gravel packing is attracting attention as a means of controlling these factors and contributing to the productive life of a well. That gravel packing is now substantially beyond the preliminary stage on the Pacific Coast is reflected in the 191,000 bbl, of oil produced monthly by the 66 gravel-packed wells in 11 different producing sectors. REASONS FOR GRAVEL-PACKING Gravel packing, if properly carried out, can be expected to provide the following benefits: 1. Prevent the movement of sand and thus eliminate sand production and sand fills, and prevent the formation of cavities. 2. Provide a practical, relatively inexpensive, large-diameter hole, which will provide well-known theoretical advantages. 3. Support the walls of the hole by completely filling the space between the liner and the formation, regardless of its irregularities, and afford a support for liners. 4. Provide for more efficient pumping operations in wells by: (a) possibly utilizing the gravel as a gas trap in pumping gaseous fluids, (b). allowing deep submergence of the pump into the oil zone.

Jan 1, 1939

By William H. Hamilton

Tunnel-driving capabilities in terms of feet per hour have advanced several hundred percent in the last century. Indications are that this capacity will double each decade for the next three decades. These future improvements will be made possible by a greatly increased need for underground excavation and the awareness of industry of its own latent capabilities. The factors of most interest to any potential user of a tunneling machine are those making possible an increase in production. The first and most obvious factor, and probably the one that has created the excitement and interest of most people, is the increase in boring rate through faster rock fracture and improved support systems. Boring rate can be increased by more horsepower in the form of increased thrust, torque, and cutterhead speed, and by better cutters and cutting methods, better material-handling systems, and better ground-control systems. All of these items are extremely important and are the basis of much discussion and effort by everyone concerned with the excavation of tunnels by machine. The second factor, just as obvious and equally important as an increase in boring rates, is "increase in production through better utilization of the tunneling machine and related equipment," which means a reduction in downtime through greater reliability of equipment. Mechanical rock attack is presently capable of cutting hard rock at 5 fph and soft rock at more than 20 fph. In current practice, however, this advance rate is maintained for less than 50% of the shift time. I predict that tunnel-driving contractors and their supporting manufacturers of tunnel-boring equipment will provide machinery that will maintain these advance rates for more than 90% of the shift time. This increase in effective production will be due to the increase in reliability of the tunneling machine and tunneling system components. Such a percentage increase in utilization of the tunneling equipment is just

Jan 1, 1970

By E. Swartzman

THE free-swelling index, a numerical value for the free-swelling properties of coal, is being used to an increasing extent in specifying coal for burning in various types of equipment. The empirical standard ASTM method for determining this index uses, as a source of heat, a gas burner which requires frequent calibration because gas pressures are not constant, relatively small changes in gas pressure resulting in rather wide variations in the temperature attained in a crucible and thus in the resultant size of the coke button. Furthermore, the quartz crucibles specified for the test are not standard equipment, and relatively small variations in dimension and wall thickness from those specified often result in rather wide variations in the resultant size of the button.

Jan 10, 1951

Prof. Mathesius analyzes the running of Howland's furnace No. 19, according to the method described by him in Stahl and Eisen, 1916, Nos. 30 and, 31, and in his work "Die physikalischen und chemischen Grundlagen den Eisenhüttenwesens" (Spamer, Leipzig). By assuming 500 Cal. lost from the hearth by radiation and cooling water per kilogram of pig iron made, a throat-gas temperature of 600° C., and taking the ratio of C02/CO as 0.64, he finds that his diagram would show 0.68 kg. of carbon oxidized per kilogram of pig iron, while Howland gives 0.66 kg. He expresses himself as well satisfied with this test of the accuracy of his theory. Making the further assumption that the heat losses from the shaft are 1,000 Cal. per kilogram of pig iron (twice as

Jan 5, 1917

By E. A. Stevens

IT has been ascertained in recent years that certain rocktypes, geological formations and structural conditions may be used as fairly reliable guides, when prospecting in recognized mineral belts or mining districts, with a reasonable certainty of discovering "pay-ore;" and that such is considered as a practically established conclusion may be inferred from a perusal of the recent reports of the U. S. Geological Survey and the literature of the several scientific societies discussing minim, geology, and kindred subjects. Cripple Creek is no exception to this conclusion, and the rock-type or association, rather than the structural condition, is the most infallible guide.† These guides consist of four, possibly five, dike-rocks, three of which are extremely basic, while the fourth is an acid rock of an entirely dissimilar character. The basic rocks are nepheline-basalt, limburgite, feldspar-basalt and tephrite. There are grounds, however, for believing that the two latter are subdivisions of one type, and therefore will be described under one head. The acid rock is quartz-porphyry. Nepheline-basalt is-a rock encountered in but few localities elsewhere on this continent, and occurs in narrow dikes cutting various formations. When typical‡ it is composed of

Jan 1, 1913

By W. R. Davison, C. A. Brown, J. P. Carstens

INTRODUCTION The phenomenon of heat-weakening of rock with 10.6 micron radiation from a continuous-wave C02 gas laser has been investigated in detail at the Massachusetts Institute of Technology for over 5 years. The programs at MIT have explored the basic nature of the heat-weakening phenomena and rock fracture caused by heating (e.g., Refs. 1 and 2), and have resulted in quantitative estimates of the relationship between the amount and parer level of heating and the resulting decrease in the modulus of rupture of a rock beam in a three-point bend test (Ref. 3). Results of the tests reported in Ref. 3 indicate a greater than 90% reduction in the modulus of rupture for granite beams heat-weakened by a laser. These results prompted the U. S. Department of Transportation to seek an assessment of the expected feasibility of employing the heat- weakening concept in a full-scale tunnel boring operation. Present- day continuous rock-tunneling machines have demonstrated tunneling time and cost savings over drill-and-blast methods, when used in rock types that are easily broken by the cutters. However, cutter bits have not yet been developed which can easily penetrate very hard rock

Jan 1, 1971

By R. G. Bowman

LEAD is a dull and sober metal, and in times of economic stress it en- joys, or at least occupies, a position which partakes somewhat of its physical lethargy and stability. The past ten years have witnessed in this country a decline in the production of lead, and a shrinkage of ore reserves, following closely the general economic situation. Metal prices have not justified exploration and development of new sources. Momentary rallies in industry have brought no response from lead.

Jan 1, 1940

Jan 1, 1886

The Keweenaw Peninsula in the Upper Peninsula of Michigan is plagued with abandoned prospectors' test pits and mine shafts, the result of exploration and operation of mines for over 100 years. The Fort Wilkins State Park in Keweenaw County alone has three open prospectors' pits within its boundaries, protected by wooden fences and maintained by the (Michigan State Conservation Department as a tourist attraction.

Jan 1, 1967

By C. Michael Dickinson

In support of the DNA Deep Basing Program, SRI International has been performing scale model experiments on protective structures since 1973. The SRI program includes field and laboratory tests of mini- structure models with surrounding natural or simulated geology. This paper contains a synopsis of some of the results of this research.

Jan 1, 1984

By J. E. Lawver, B. J. Clingan, R. E. Snow

Response surface methodology is a well-known and powerful technique for determining optimum conditions in flotation systems. One disadvantage is the onerous task of the numerical calculations and curve plotting. This paper describes a system in which the investigator simply selects the range of several flotation variables after which the design of the experiment, data analysis, generation of response surface equations, and response surface plots are automatically carried out using a digital computer and a computer-driven curve plotter. Several typical response surfaces of important variables in phosphate flotation are presented as examples.

Jan 8, 1979