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By Ernest A. Hersam

IN every commercial establishment,' it is customary and necessary to take inventory, periodically, and to account for profits and detect losses, to achieve productiveness and enhance efficiency. So, too, in the ordered life of every individual, there is the need of periodic introspection. The exercise of the Sabbath for rational thought, the utilization of pause, or rest, from the technique of daily occupation, orient the efforts. These are the constructive opportunities by which we grow always better than we were. Thus, also, there' is need of a periodic analysis of the organizations to which we belong and toward which we con- tribute. So we find' reason for the fitness of our loyalty. There seems to be no half-ground for the engineer. Whatever presumes to bear his name demands either the crushing pressure of his heel or the supporting pressure of his hand.

Jan 1, 1929

By F. A. Olson, S. L. Pohlman

A unique method of measuring weight loss as a function 3 of time, with a sensitivity of 10-5 grams, while leaching copper minerals with a flowing acid leach solution has been developed. Kinetic results obtained coupled with visual and microprobe analyses show topochemical reaction for the leaching of chrysocolla with sulfuric acid. The kinetics follow a shrinking core model and show ion diffusion through a product layer, chemical reaction at the unreacted core interface and mass transfer through the boundary layer as being important.

Jan 1, 1974

By V. Annamalai, J. B. Hiskey

Abstract-The kinetics of copper cementation on a rotating disc of pure aluminum were studied as a function of chloride ion concentration, rotational speed of the aluminum disc, hydrogen ion concentration, copper ion concentration, and temperature. The optimum experimental conditions for all the parameters were determined. Chloride ion was found to destroy the naturally existing aluminum oxide film, and enabled the cementation reaction to proceed. A two-step rate, observed in most of the experiments, was attributed to the attainment of a roughened surface. An Evans diagram for the copper-pure aluminum system was constructed and utilized in predicting the controlling mechanism of the system. At low temperatures (<33°C), the rate with an experimental activation energy of 20.36 kcal mol-1 was controlled by the presence of an oxide layer. While at higher temperatures presence of an oxide layer. While at higher temperatures (>33° mol-1 was controlled by ionic diffusion. The deposits obtained were pure copper and not a copper-aluminum alloy. The amount of aluminum dissolved was determined for each experiment, and the maximum excess consumption was found to be only 40%. The structural characteristics of the copper deposits were studied using a scanning electron microscope. These observations indicated that the deposits were either bulbous, massive crystalline, or dendrites of different degrees of fineness depending on the experimental variables. The reaction rates seemed to depend on the deposit structures in a predictable way when a particular experimental parameter was varied.

Jan 6, 1978

By V. Annamalai, J. B. Hiskey

The kinetics of copper cementation on a rotating disc of pure aluminum were studied as a function of chloride ion concentration, rotational speed of the aluminum disc, hydrogen ion concentration, copper ion concentration, and temperature. The optimum experimental conditions for all the parameters were determined. Chloride ion was found to destroy the naturally existing aluminum oxide film, and enabled the cementation reaction to proceed. A two-step rate, observed in most of the experiments, was attributed to the attainment of a roughened surface. An Evans diagram for the copper-pure aluminum system was constructed and utilized in predicting the controlling mechanism of the system. At low temperatures (<33°C), the rate with an experimental activation energy of 20.36 kcal mol- 1 was controlled by the presence of an oxide layer. While at higher temperatures presence of an oxide layer. While at higher temperatures (>33° mol- 1 was controlled by ionic diffusion. The deposits obtained were pure copper and not a copper-aluminum alloy. The amount of aluminum dissolved was determined for each experiment, and the maximum excess consumption was found to be only 40%. The structural characteristics of the copper deposits were studied using a scanning electron microscope. These observations indicated that the deposits were either bulbous, massive crystalline, or dendrites of different degrees of fineness depending on the experimental variables. The reaction rates seemed to depend on the deposit structures in a predictable way when a particular experimental parameter was varied.

Jan 1, 1979

By M. E. Wadsworth, P. H. Yu, C. K. Hansen

A study of the rate of dissc5lution of chalcopyrite (CuFeS2) in acidic solutions under oxygen overpressures was carried out by measuring the rate of formation of cupric ions in solution. Effects of temperature, oxygen partial pressure, surface area, and concentration of sulfuric acid were evaluated. A sized batch of chalcopyrite was leached in the temperature range of 125° to 175°C and in the pressure range of 75 to 400 psi of oxygen. In 0.5 N H2SO4 all products of reaction went into solution except for trace amounts of elemental sulfur. The dissolution of chalcopyrite followed linear kinetics and was essentially independent of hydrogen ion concentration for H2S04 concentrations between 0.2 and 0.5 N. The oxygen dependence indicated adsorption approaching limiting values with increasing oxygen pressure. The linear mechanism was explained in terms of steady-state adsorption of oxygen at the chalcopyrite surface followed by a surface reaction. The enthalpy of activation for adsorption of oxygen was found to be approximately 33 kcal per mole. An activation enthalpy of approximately 9 kcal per mole was observed for the surface reaction. Charge transfer reactions are not rate controlling in the process.

Jan 1, 1973

By G. Gabra

The kinetics of acidified thiourea leaching of pyrite concentrate was investigated at temperature ranging form 20 °C to a 60 °C. The effect of various parameters on the dissolution rates are discussed. The gold extraction was found to be zero and first orders with respect to Fe (111) and thiourea concentration, respectively. The order of the reaction with respect to sulfuric acid was found to be zero. The activation energy was determined from the Arrhenius plot as 2,039 kcal mole -1 (for a freshly prepared acidic solution containing Fe (111) as the oxidant and at 800 rpm stirring speed. This relatively low activation energy value suggests that the gold extraction is controlled by a-physical phenomenon. Under optimum conditions, more than 90% of gold has been dissolved in about 30 min. and 95% in 60 min. Attempt to recover gold from thiourea solution using active carbon is also discussed.

Jan 1, 1984

By Milton E. Wadsworth, W. Martin Fassell, William H. Dresher

A study of the rate of dissolution of molybdenite (MoS2) in alkaline solution was carried out under carefully controlled conditions. Effects of temperature, oxygen over-pressure, and KOH concentration were evaluated. Studies were made in the temperature range 100°C to 175°C and in the pressure range 0 to 700 psia of oxygen. Under these conditions molybdenite was found to leach according to a linear mechanism. Both oxygen over-pressure and KOH concentration were found to control the rate of leaching. The mechanism has been explained in terms of adsorption of oxygen at the molybdenite surface followed by configurational rearrangement of the adsorbed molecules. The hydroxyl ion dependency is believed to be diffusion-controlled. Laboratory batch studies have shown that molybdenite can be readily dissolved in alkaline solutions under moderate conditions of temperature and pressure. Commercial application of this process to the production of ferro-molybdenum and molybdenum chemicals is promising in view of the ease of dissolution of molybdenite and the relatively noncorrosive conditions involved in the process.

Jul 1, 1956

By JOSEPH MACDONALD

STRIPPED of its romantic possibilities, mining is a commercial business, carried on for the profit there is in it, and the business of the manager, in its ultimate analysis, is to make the profit as large as possible. The general manager of a mining company should keep himself personally familiar with all the details of its operations. If be fails to do so, chaos results, labor becomes inefficient, costs go up, and profits go down. Nowhere is this emphasized more than in Mexico. If the mining operations are extensive and complex, involving, besides the work of mining the ore, its transportation and treatment by various milling operations, and the marketing of the products, the business, to be carried on properly, must be divided into a number of main departments, which are subdivided into minor departments. Each main department should be under the immediate charge of a superintendent, or a foreman, and each minor department under a shift-boss. Organized in this way, and with all the principal centers of activity connected by telephone, the manager can keep in touch at all times with the details of every branch of the business, and be in a position to perform effectively the full duty of manager. The ?total cost of mining operations may be broadly divided under the heads of Labor, Supplies, and Marketing. Of these, it will be found, on averaging a number of cases, that the cost of labor will be about two-thirds of the total cost. The importance, therefore, of an efficient labor-department will be apparent. This department must be sub-divided and organized differently, according to the peculiar conditions at each mine, and no one system, however well suited for one particu-

Jan 1, 1909

By C. L. Clark, J. Russ

FOR many years attempts have been made to develop a laboratory test that would serve to indicate the proper temperatures to be used in the various hot-working applications to which metals may be subjected as they are being processed from the cast ingot to the desired finished products. That these attempts have not been very successful is indicated by the fact that most of the temperatures in use today in these operations have been developed over a period of years by trial and error. In other words, the selection of the proper temperatures for the hot-working of metals is generally an art rather than a science. Our knowledge with respect to the behavior of metals at elevated temperatures has been greatly extended during the past several years. While most of the work in this field has been done at proposed operating temperatures of equipment, rather than at processing or fabricating temperatures, one outstanding fact has been developed, which is applicable to the entire high-temperature range; that is, that the rate of deformation to which the metal is subjected is of the same order of importance as the temperature. The failure to properly recognize this fact has greatly retarded the development of a suitable laboratory test for determining hot-working temperatures. INFLUENCE OF RATE OF DEFORMATION ON HIGH-TEMPERATURE PROPERTIES It is not the intent of this paper to survey all the work that has been done on the effect of deformation rate on the properties of metals. The importance of this factor, however, was shown by Zay Jeffries1 as early as 1919, when he called attention to the existence of the so-called equicohesive temperature and to the effect of certain factors on the location of this temperature. Fig. I is a diagrammatic sketch showing the effect of temperature on the relative strength of the crystals and grain boundaries and the type of fracture that will result, depending on the location of the test, or working temperature with respect to the equicohesive temperature. Since the type fracture varies, it also follows that at temperatures below the equicohesive temperature the major deformation occurs in the grains; while at temperatures above, the deformation results either from the movement of the grains with respect to each other or recrystallization of the strained material occurs almost instantaneously, producing new crystals at the fracture. As previously indicated, it is an established fact that the position of this equicohesive temperature for any given metal is dependent on the deformation rate. For example, in 0.15 per cent plain carbon steel the location of this temperature under

Jan 1, 1945

By A. M. Gow

THE trend in ball milling has been toward mills of larger diameter, but without fundamental laws as a guide. The speeds at which mills are run have been a matter of cut-and-try. This paper deals with both diameter and speed and proposes to show the laws which apply to some laboratory ball mills, ranging in diameter from 18 to 42 in., run at various speeds. The correlation of power, speed, and grinding rate of the respective mills will be shown by curves of markedly significant similarity. Before presenting the results some consideration will be given to the mechanics of ball milling.

Jan 1, 1930

By Kalanadh V. S. Sastry, D. W. Fuerstenau

Design and operation of a batch balling drum that can be used easily for experimental investigation of the balling or granulation behavior of particulate materials are described briefly. An experimental procedure for ascertaining the growth kinetics of iron ore concentrates or other particulate materials with this kind of apparatus is outlined.

Jan 1, 1972

By Joseph J. Yancik, Leonard L. Felts, George B. Clark

Little information has been published concerning the actual or useful amount of energy obtained from explosives when they are used for blasting. To provide more data on this subject, 8-in. neet cement cubes were blasted in a steel plate box and the breakage energy evaluated by comparison with drop crusher results using Rittinger&apos;s," &apos; Kick&apos;s,%nd Bond&apos;s&apos; theories. Theories by Bond and Wang," Lineau,&apos; Hatch,&apos; Roller," and others were not considered applicable. Those used in this investigation may be expressed mathematically as follows: [ ] The above equations were employed to determine values of KK, K for particle size distributions similar to those obtained from the blasting curves. These values were in turn used as a means of approximating the specific energy of the blasted material. The efficiency of crushing by blasting was then determined by dividing this specific energy by the maximum available work of the explosive per gram of cement.

Mar 1, 1956

By Bjorn N. P. Paulsson

A number of granitic rock specimens have been studied from the Stripa mine site in connection with a large-scale geomechanics research program. The purpose of the program was to evaluate and develop field and laboratory techniques for rock mass characterization and to determine design parameters for storage of nuclear waste. In this paper a minicomputer-based technique for studying dynamic rock properties in the laboratory is described, together with results from the tests. The specimens were tested under different uniaxial and saturation conditions. Specimens from a field-heated rock mass were also tested to determine if temperatures typical of those encountered with nuclear waste would introduce additional fracturing. Both Vp and Vs increased with stress for both saturated and dry specimens. Both Vp and Vs were higher for saturated specimens at all stress levels compared with the dry. The velocities increased linearly or near linearly with saturation. The test results on the previously heated samples indicate that attenuation is more sensitive to thermally-induced microfracturing than velocities. Analysis of the attenuation values with stress show that rock heated to 200°C is damaged, and that the damage is in form of low-aspect ratio fractures.

Jan 1, 1984

By A. V. Pegler

As with most rheologically defined materials, rocks react differently in different environments to similar forces. Physical changes and deformations depend as much on the rate of change of stress as the magnitude of stress. In many instances the rate of change is more important. Under load, all real materials will flow if given time. If there is no time for flow, materials tend to react in a brittle manner. Particular characteristics are developed in rocks during their periods of formation and postformative geologic history. Whatever their mode of occurrence, rocks are a record of their formation and changes. Where analyses are possible, advantage should be taken of the natural inherent characteristics to help design economical functional structures. A number of techniques of measurement and analysis have been developed. The fracturing of rock by hydraulic pressure has been examined by many authorities but few within the scope of available published literature have used the actual rocks concerned in tests to examine directional characteristics or preferred strain propagation rates and directions. In a number of investigations of the properties of rocks for mine design purposes and stress analysis problems in which the writer has been associated, it has been demonstrated that there are definable preferred shear planes in most rocks. Preferred shear planes can be identified by a photoelastic method of analysis, and the information can be used to improve design of optimum drilling and breaking directions for mining purposes. Definable principal strain directions can be determined to facilitate design directions of optimum stability for permanent mine openings. In field fracturing operations the same directional characteristics as outlined above should be used to define preferred fracturing directions as in the laboratory from oriented samples. It is mainly with this aim that

Jan 1, 1968

By Tadeusz Cyrul

Results of a large scale compression test in situ are the subject of discussion. A cube of coal having an edge length of 1.5 meters was subjected to uniaxial compression tests in situ. At the same time both load and deformation were controlled. Deformations were measured on 60 short measurement bases, each 23 cm in length. The bases were uniformly distributed on the side surface of the cube, forming five horizontal rows and twelve columns on the development of the surface. Readings were taken from each gauge for each level of loading which was increased step by step. Due to heterogeneity of the rock, readings showed scatter. Scattered data were approximated by a plane, using the least squares method for each row separately and for the entire population of bases. Orientation of the planes are analyzed. The geometrical measure of the bending moment is introduced. It shows that the magnitude of the bending moment and the bending plane differed from row to row, thus implying that the cube was not only bent but twisted as well. This complex behaviour of the coal cube is apparently caused by its heterogeneity and vertical anisotropy. The results constitute a contribution to the verification of existing design criteria on the stability of mining pillars.

Jan 1, 1984

OF what use is the federation to me and why should I support it?" is a question that has been asked by many members of the constituent societies of the F. A. E. S. during the last year; a question that is asked because the speakers do not realize what the Federated is doing or what is the field of its activities. "What is it doing for the profession and for mankind?" would be a more appropriate question, the answer to which is found in the closing chapter of Prof. Cassius J. Keyser&apos;s "Mathematical Philosophy."&apos; The chapter is entitled "Science and Engineering." Professor Keyser writes from the layman&apos;s point of view. He is looking at the profession and at engineers from the outside. We have in his thoughts the oppor-tunity that Burns sought when he wrote "Oh wad some power the giftie gie us to see oursels as ithers see us." With the permission of the author and the publisher, we quote the following paragraphs: A layman, viewing a profession from the outside, seeking thus to ascertain its proper relations to the common weal, may bring to the task a certain freedom, which, were he a member of the profession, he might have lost. "Men trained in a profession," said Prof. David Swing, "come by degrees into the profession&apos;s channel, and flow only in one direction, and always between the same banks. The master of a learned profession at last becomes its slave. He who follows faithfully any calling wears at last a soul of that call-ing&apos;s shape. You remember the death scene of the poor old schoolmaster. He had assembled the boys and girls in the winter mornings and had dismissed them winter evenings after sundown, and had done this for fifty long years. One winter morning he did not appear. Death had struck his old and feeble pulse; but, dying, his mind followed its beautiful but narrow river-bed, and his last words were: It is growing dark-the school is dismissed-let the .girls pass out first."&apos; I shall not be so much concerned with the present status of the science as with its potency and promise. Of individual engineers the ideals may be high or low, worthy or unworthy; but of engineering itself the ideal is great and mighty. It is of that ideal that I intend to speak.

Jan 9, 1922

By F. P. Haver, M. M. Wong

The Federal Bureau of Mines has developed a leach= electrolysis method for recovering lead from galena (PbS). Flotation concentrate is leached with ferric chloride (FeCl3) solution to obtain lead chloride (PbC12) and elemental sulfur, PbS + 2FeC13 -+ PbC12 + 2FeC12 + Sº. Over 99% of the P~S in the condentrate is converted to PbC12. The leach solution, composed of brine (NaC1) and FeC13, dissolves the PbC12 as it is formed, leaving a residue of elemental sulfur plus gangue. Very pure PbC12 (>99.9%).is crystallized from the leach filtrate on cool- ing and is subsequently electrolyzed in a fused-salt bath to obtain molten lead metal (>99.9% Pb). Spent leach solution (FeC12) is regenerated for further use by reaction with the chlorine obtained in the electrolysis of lead chloride, and other values, such as Ag, Cu, Zn, and Sº, are recovered by additional treatments of the leach solution and leach residue. This paper discusses results and conditions of the leaching and electrolysis operations.

Jan 1, 1976

WHEN one leaves the busy street and enters a library, the closing of the door behind him marks his passage into another world. Outside is the world of phenomena and appearances-of thronging pedestrians bustling about their business, of gregarious sights and sounds, of insistent auto-mobiles. Inside, on dusty shelves, is the stored learning of civilized man-the recorded ideas of countless generations. It is somewhat of a magic world. Here are the theories and secrets for which thousands of men toiled and gave their heart&apos;s blood. To produce one book on one phase of an ob-scure-subject may have required the best efforts of a group of men unique in their period. To prove one theory, or es-tablish a single application of a theory, may have taken the devotion of a genius who sacrificed his life to his work. This theory is perhaps stated in one paragraph of unassum-ing type, and the library contains millions of such para-

Jan 11, 1927

By C. E. Abbott

THE Birmingham district, Alabama, is distinctive in the proximity to one another of its deposits of iron ore, coal and flux. These three basic requisites for the making of iron and steel are found within a radius of 10 miles. Both dolomite and limestone are produced, the former for blast-furnace flux and the latter for basic open-hearth operations. The Tennessee Coal, Iron and Railroad Co., a subsidiary of the United States Steel Corporation, operates a limestone mine at Muscoda, near Bessemer, 12 miles southwest of Birmingham, served by its own railroad transportation system. The mine has a capacity of 130 tons per hour. Average analyses of a recent month&apos;s production are as follows: Fe2O3 Si02 A12O3 CAC03 MGCO Lump, per cent 0.51 0.22 98.63 0.14 Crushed and washed, percent 0.70 0.26 98.36 0.18 Lump stone, 2 1/2 to 7 1/2 in., is used in open-hearth operations at Fairfield Steel Works. Fine crushed and washed stone, 1 ¼ to 0.063 in., is calcined at the, lime-burning plant and used for lime charges at the Ensley open hearths.

Jan 1, 1936

By J. E. Nesset, J. A. Finch

A model of the fully-loaded condition of particle accumulation on the matrix of a high gradient magnetic separator is developed. The model accurately predicts the build-up profiles reported recently by Friedlaender et al. A powerful development from the model is that loading (volume of accumulated material per unit volume of matrix) is uniquely defined by a dimensionless group, called the loading number, NL. From direct measurements, NL proved superior to the dimensionless group proposed by Watson as a measure of loading. The fine size limit of hematite recovery is examined using NL.

Jan 1, 1980