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By G. H. Shefelbine

DISCOVERED during the time of the Spaniards, the Namiquipa silver-lead-zinc mines in Chihuahua, Mexico, remained idle until 1916, when mining claims were first denounced. About 1922 a Japanese company, the Santo Domingo Mining Co., was formed to mine the oxide silver ore. The company built a 75-tpd cyanide plant and mined in the area for a number of years. Because of an error in surveying in one of the company's mines situated in another district, mining was carried over into a claim owned by General Marcel Caraveo, at that time governor of Chihuahua. Santo Domingo Mining Co. lost the resulting lawsuit and consequently had no capital to continue operating at Namiquipa. Later, Ray Brown and Eugenio Caballero formed a company to operate the mine, shipping crude ore to the American Smelting and Refining Co. smelter at Avalos, Chihuahua. The cyanide plant was changed to flotation with a capacity of 75 tons per 24 hr. In 1936 the property was again closed owing to labor trouble, a drop in the price of silver, and increased water in the mine.

Jan 10, 1957

By E. Hoek

INTRODUCTION Rock slope stability research has been in progress for the past four years at the Royal School of Mines in London under the sponsorship of a consortium of 23 companies* with interests in open pit mining. This paper reviews the principal aims and achievements of this research project. In order to assist the reader in following these details, the basic philosophy underlying the formulation and direction of this research project is discussed. DISTRIBUTION OF RESPONSIBILITY In open pit mining, the economic necessity of keeping waste rock removal to a minimum generally means that the mine slopes have to be excavated to the steepest possible slope angle. On the other hand, excessive steepening of these slopes can induce failures, which may negate the economic benefits that have been aimed at and which may also result in loss of life and damage to equipment. Consequently, where slope failures are likely to prove to be a problem, an evaluation of the stability of the slopes to be created should be included as part of the overall pit design. How is the stability of a rock slope evaluated? When this question was examined, during discussions on the research policy to be followed at the Royal School of Mines, it was clear that relatively few satisfactory techniques were available in a form that would be comprehensible and therefore useful to the practical mining engineer. It was recognised that the research project must be directed towards two distinct aims: a) The evaluation of existing techniques for rock slope stability analysis and the provision of new techniques where these existing methods were found to be inadequate and b) The presentation of the results of this evaluation and research in a form that would be useful to engineers without specialist training in rock mechanics. It was soon realized that a university based research team, however large and efficient, could not achieve these aims without the co-operation and assistance of mining engineers,

Jan 1, 1972

By Roman Šejnoha, Karel Mazanec

A pronounced tendency for delayed fracture zoas observed in the martensite structure of low-alloy steels in the as-quenched condition. Cracks of predominantly intercrystalline nature nucleated and propagated at stresses substantially lower than the short-titne tensile strength of- the steels, and were observed even in hydrogen-free speciunens. The occurrence of delayed fractures in the as-quenched condition is interpreted as a supevposition of the effect of free dislocations generated during the martensite transforlnation, and of a weakening of the prior austenite grain boundaries caused by dynamic shocks exerted on the boundaries by growing martensite plates. AN important metallurgical problem, connected with the production and use of high-strength steels, is delayed fracture in martensitic structures. Such fractures occur in quenched steels as a result of prolonged loading with external stresses far lower than the short-time tensile strength of the steel. The same effect can be produced by sufficiently high internal stresses: it is well-known that quenched structures will in some cases crack intergranularly at room temperature if not tempered quickly enough even in the absence of any externally applied stress. In Troiano's papers1,2 on delayed fractures in high-strength steels, the fundamental role of hydrogen migrating under the influence of multiaxial stress towards the nuclei of cracks was found. Fig. 1 shows the typical relationship between stress and the time to fracture found by Troiano in hydrogen-charged high-strength steels. On the other hand, Shurakov 3,4 explains the realization of delayed fractures in martensite as due to a "quasi-viscous" behavior of the austenite grain boundaries immediately after the martensitic transformation. 1) MATERIALS AND EXPERIMENTAL METHODS Two low-alloy steels of commercial purity were used for the experiments reported in this paper. Their chemical composition is shown in Table I. The heats were melted in a laboratory furnace, cast to ingots, forged to bars of 3/4 in. diameter, and annealed. Machined test pieces were heat-treated as follows: Ni-Cr-Mo steel held at 900°C for 30 min and quenched in oil; Mn-Si-Cr steel held at 900°C for 30 min and quenched in water. For the delayed-fracture tests, notched cylindrical test pieces, Fig. 2, stressed in torsion, and unnotched cylindrical tensile-test pieces, 1/4 in. diameter, were used. The specimens were normally loaded with a constant static load 45 min after quenching for the torsional tests and 10 min

Jan 1, 1965

By C. G. Dunn, J. L. Walter

SILICON-iron .under certain conditions of processing and annealing will form a cube texture. The occurrence of this texture in thin tapes of silicon iron was first reported by Assmus, Detert, and Ibe.' They concluded that the cube texture in their material formed by a secondary re crystallization process. In the course of present investigations on the development of the cube texture and the mechanisms involved in its formation by secondary re-crystallization it was found that under certain conditions the cube texture was replaced by a cube-on-edge or (110) [001] texture. We call this phenomenon tertiary re crystallization since it follows secondary recrystallization. The secondary recrystallization occurs after primary recrystallization and a substantial amount of normal grain growth. It is the purpose of this paper to describe briefly the occurrence of tertiary recrystallization and the structure and texture prior to and after tertiary recrystallization. The primary and secondary recrystallization structures and textures are the subject of another study and will be referred to briefly in the discussion of results. Evidence will be presented for the view that the dominant driving force for tertiary recrystallization is derived from the surface free energy which depends on the crystallographic planes presented to the gas-metal interface. In the absence of boundary restraining forces (dispersed phases, thermal grooves, and so forth) a sufficiently large difference in surface free energy across a grain boundary would produce boundary migration away from the center of curvature of the boundary intersection line in the surface of the sample according to risher.2 Therefore, particular attention was paid to observation of the direction of motion of these surface boundary lines. Furthermore, measurements of the actual boundary curvatures could be used to estimate the driving force supplied by surface free energy. EXPERIMENTAL PROCEDURE Samples were prepared by hot and cold-rolling vacuum-melted ingots of iron containing 3 pct Si to strips 0.012 and 0.006 in. thick. The ingots contained less than 0.005 wt pct impurities. The rolled strips were cut into samples approximately 1 in. wide by 3 in. long and were electropolished to remove surface imperfections. All samples were annealed in a vacuum at a pressure of approxi-

Jan 1, 1960

By L. L. Oriard

In order to predict the influence of blasting on slopes, one must first understand the action of explosives, the manner in which rock is broken or displaced, and how seismic waves are transmitted, and the nature of these seismic waves. In this paper, the author describes the action of high explosives on rock masses, beginning at the source of the explosion, extending through the zone of rupture to a distance where only elastic waves of low energy persist. The paper describes the relationships between explosives charge quantities and distances, including the character and intensity of the seismic waves in various types of terrain. In looking at the analysis of slopes subjected to seismic waves, it has been common practice to assume a simplified model in which the anticipated acceleration is applied horizontally to the slope as an equivalent static force, or a model in which there is a rigid base subjected to mechanical shaking. Such models do not accurately portray blasting activity taking place within or near the slope in question. In dealing with blasting effects, it is important to under- stand seismic wave types, wave lengths, attenuation and transmission paths, as well as vibration intensity. In most cases, those slopes that are the least stable under static loading will also be the least stable under dynamic loading, although there may be rare exceptions. Thus, the more that is known about a slope statically, the better will be the assessment of it dynamically.

Jan 1, 1983

By Samuel B. Christy

The present paper is a continuation of a study of the reductionworks of New Almaden, the first part of which was published under the title " Quicksilver-Reduction at New Almaden," in the Transactions of this Society, vol. xiii., p. 547.* Frequent reference will be made to some of the data there given. The following is an outline of the contents of this paper: I. Condensing appliances used at New Almaden: a. Brick condensers, b. Iron condensers—flues and " water-backs," c. Glass and wood condensers, d. Friction-coudensers—filters and revolving screens, e. Flues, towers, and chimneys. II. Analysis of condensing-systems. III. Temperature of condeusers. IV. Product of condensers. V. Treatment of soot. VI. Losses of treatment: a. Nature of losses, b. Composition, weight, and volume of dry gases, c. Volume of wet gases, d. Specific weight of quicksilver vapor, e. Vapor-loss at various temperatures. VII. Comparison with New Almaden practice. VIII. Comparison with results at Idria, Austria. IX. Comparison with results at Almaden, Spain. X. Future improvements in quicksilver-condensation. I. Condensing Appliances. The complete condensation of mercurial fumes in a large way presents numerous practical difficulties, familiar to all who have had to retort amalgams. In condensing the quicksilver-fumes discharged

Jan 1, 1886

By F. J. Smit, S. C. Sun

Flotation variables were investigated for the re-clamation of phosphate from a Florida washer slime. Under optimum conditions, 92% of the phosphate was recovered. Further cleaning of the rougher flotation concentrate resulted in a product containing about 30% P2O5 with a phosphate recovery of 65%. The enormous amount of slimes rejected in the Florida pebble phosphate fields, containing roughly one-third of the phosphate in the pebble matrix,1 has long been considered as a serious problem to the industry. The mere disposal of these slimes has posed an almost insurmountable task for several investigators.2-5 Some companies still resort to huge surface dams, some covering 1800 acres, for slime disposal.6 Information on the recovery of fine phosphate from these slimes is scanty. Dry separation8 and electrostatic beneficiation8 were suggested, but would necessitate radical changes in the present mining and concentration methods. Haseman10 proposed the selective flocculation of colloidal phosphate with starch, while Ralston11 suggested the removal of clay from the matrix by amine flotation. Leaching of the slimes for recovering the small amount of uranium was attempted by the Battelle Memorial Institute12,13 but proved to be economically unfeasible. The purpose of the present investigation was to determine the optimum fatty-acid flotation conditions for reclaiming the phosphate discarded with the Bartow washer slime. Prior to the flotation experimerits, however, the size distribution and the minera-logical composition of the employed slime had to be determined.

Jan 1, 1963

By C. M. Tucker, K. R. Van Horn, W. P. Sykes

Recent investigations of the molybdenum-carbon alloys have been reported by Becker and Ebertl,‡ Westgren and Phragmén2, T. Takei3, and H. Tutiya4. Takei3 studied the Mo-C system by employing metal-lographic and X-ray methods, and the other publications described the determination of the crystal structure of the molybdenum carbides. In exploring this system by a technique previously applied to the tungsten-carbon series5, the results of Takei were confirmed with two definite exceptions; i.e., first the composition of the eutectic, and second the nature of the carbon-rich intermediate phase. Consequently, a more thorough examination of the molybdenum-carbon constitution was initiated in an effort to correlate the data supplied by the microstructures, diffraction patterns and chemical analyses. Metallographic Investigation A briquette of molybdenum powder when heated in a carburizing atmosphere at 1500" to 1600" C. for several hours develops the carbon-rich layer shown in Fig. 1. The carburization was accomplished by placing the briquette in a carbon tube, which was heated in the hydrogen atmosphere of an alundum muffle wound with tungsten resistor. While the macrostructure indicates two distinct shells, and suggests the possibility of two carbon-rich phases, no evidence of this condition could be detected by the microscope, which revealed but one high-carbon constituent. This carbide forms next to the molybdenum as a relatively dense, light-colored zone (Fig. 2) which passes abruptly into an outer layer of spongy texture. As will be noted later, only one intermediate phase was observed in the X-ray photograms prepared of different locations in the carburized zone. The metallographic structure at the inner border of the shell, reproduced in Fig. 3, shows a marked porosity accom-

Jan 1, 1935

By D. W. Mitchell

While pure magnesium does not corrode rapidly the presence of even very small quantities of certain other metals accelerates corrosion remarkably. Because magnesium is such an electropositive metal (E° = +2.34 volts)' the presence of substances that permit galvanic activity is extremely undesirable. It is stated that as little as 0.017 pct of iron in magnesium causes a marked increase in the corrosion rate.2 Magnesium and its alloys are commonly melted in iron or steel pots; consequently the commercial metal has the opportunity to pick up iron if it has that tendency. Quantitative data on the solubility of iron in magnesium are of practical as well as of academic interest. Some magnesium alloy castings tend to have large grain size unless suitable treatment is given to the liquid metal just prior to casting. One method of grain refinement consists of "superheating" the metal just prior to casting. "Superhcating" is heating to a temperature 100 to 200°C above the casting temperature and holding for a short period of time. Superheated metal has a much finer grain than unsuperheated metal. A satisfactory explanation of this phenomenon has not been forthcoming. One hypothesis attributes the grain refinement in the superheated metal to precipitation of some phase that is mis-cible at the temperature of superheat but not miscible just below the casting temperature and which is thought to provide nucleating centers for crystallization. This phase, if the foregoing hypothesis is correct, would probably be a metal or an intermetal-lic compound. Of the metals likely to be found in magnesium alloys, iron is one of the most likely candidates for the role of grain refiner for iron occurs in small quantities in all commercial magnesium and magnesium alloys. A. Beck³ states that magnesium, in either the liquid or the solid state, cannot dissolve iron and that iron exists as a finely divided suspension which does not settle out because of its extreme fineness. Beck also presents a micrograph showing a large iron dendrite in magnesium but does not comment on the crystallization of iron from a solution supposed to contain none. It is doubtful that dendrite formation from suspended iron -would be possible. This suspension theory is the basis of patents4 covering the removal of iron from magnesium by allowing the iron particles to act as nuclei for the formation of primary magnesium crystals which can be separated by segregation. Also covered by patents is the removal of iron by the addition of another metal to form an intermetallic compound with the iron which, because of its increased particle size, is able to settle out of the molten metal. Here, too, quantitative information on the extent of iron solubility in liquid magnesium is of more than theoretical interest. M. Hansen,5 in his critical collection of the data on binary alloys, states that iron is not soluble in liquid magnesium. W. R. D. Jones% ho studied the physical properties of low iron magnesium alloys observed a 57°

Jan 1, 1949

By Robert S. Dewey

More wells were drilled in West Texas† during 1944 than in any year since 1941. As compared with 1943, there was an 82.5 per cent increase in the total number of completed wells. The 1646 wells required an estimated 140,715 days to complete for a total of 7,632,249 ft. An average of 85 completion days was required to drill to an average of 4630 ft. This depth is approximately 100 ft. greater than that of the previous year. It is estimated that $100,000,000 was invested in drilled wells. As of Dec. 31, 1944, there were 270 field and 91 wildcat wells being drilled. While an identical number of wells were drilling Dec. 31, 1943, the proportion of wildcats increased in 1944 from 19.7 to 25.2 per cent. During 1944, oil wells were completed in 103 of the 164 fields in West Texas. Of the 1361 oil wells, 385 were in Slaughter, 116 in Fullerton, 63 in North Cowden, 62 in Fuhrman-Mascho, 59 in Wasson, 52 in Westbrook and 47 in North Ward. Approximately 22 per cent of the wildcat drilling was to pre-Permian formations. Despite the increasing proportion of wildcat wells drilled, the wildcat discovery rate has declined since the year 1942. AS compared with 1943, the number of wildcat wells drilled increased from 11.7 to 12.7 per cent and the footage in wildcat exploration increased from 13.3 to 13.8 per cent of the total. The monthly production of crude continued to increase to a peak of 15,336,000 bbl. in October 1944. As compared with a similar peak production in October 1943, there was a 37.3 per cent increase. The yearly production increased from 98,165,-ooo bbl. in 1943 to 159,943,000 bbl. in 1944, an increase of 62.8 per cent. Based upon an assumed average price of $1.00 per barrel and less 1/8 royalty, the gross return to the producer amounts to $140, 000,000. From 1943 to 1944, the average number of producing wells increased 6 per cent while the average daily production per well increased 53.1 per cent. The average daily production per well increased from 17.5 bbl. in 1943 to 26.8 bbl. in 1944. The proportion of flowing wells decreased from 50.5 per cent in January to 49.1 per cent in December 1944. Drilling With the continued shortage of labor and materials, drilling costs have risen sharply. Just how much is difficult to ascertain. Owing to competition for available drilling rigs, contractors are reluctant to assume drilling risks. In consequence, some contracts are let on a cost plus basis, or day work below some specified depth with the operator furnishing part of the consumable materials, such as mud and drilling bits. Contractors are having difficulty in maintaining full and effective drilling crews with insufficient and inexperienced labor. Service companies have inadequate labor and equipment to meet their appointments promptly. Pipe Lines The Gulf Pipe Line Co. increased the capacity of its 10-in. main line by filling in gaps amounting to 75 miles on the loops between Judkins and Weatherford, Texas.

Jan 1, 1945

By C. M. Loeb, T. E. Norman

THE use of ball, rod and tube mills for grinding ore, cement and other materials has grown so rapidly during the past forty years that the world's annual consumption of ferrous grinding media for these mills is now estimated to be between one half million and one million tons per year. Ferrous grinding balls constitute the major portion of this tonnage. Obviously they represent sufficient value to justify thorough studies' of the factor sgoverning their performance. The selection of grinding balls is governed principally by: I. Quality (wear resistance, impact resistance, soundness, and the like). 2. Sources of supply and delivered cost. 3. Grinding characteristics or efficiency in the ball mill. This paper deals principally with the quality of ferrous grinding balls. In the study of these factors certain data relative to the fundamental nature of ball wear in ball mills have been obtained. These data are also presented and discussed briefly. THE DEVELOPMENT OF A SUITABLE WEAR TEST A study of the fundamental factors governing the quality of grinding balls has been hampered seriously by the fact that a competent test has, in the past, involved the purchase of several hundred tons of balls of a specific type which were then run in one or more ball mills for a period ranging from several months to several years' duration. Often, during the period of test, it became necessary to change operating conditions or the character of the ore fed, to the test mill with the result that the rate of ball consumption changed and the test figures became of little value. Under such circumstances, progress in the development of better grinding balls, has been necessarily slow. Economic factors and variations in the quality of balls produced by different sources of supply generally make it necessary for each mill operator to determine for himself the most suitable type of balls for his mills. In our own ball mill grinding operations at Climax, Colo., we were faced with this problem. After we had run a few large scale wear tests at considerable expense we decided to investigate the possibilities of a small scale wear test which would be capable of testing numerous types of balls within a relatively short time. The most important requirement of any test is, of course, that it give results which can be used to predict accurately the wear in full scale operations. It was known that Ellis and his associates1,2 had developed a method of testing grinding balls by small scale tests run at the Ontario Research Foundation. Ellis' method of testing was used as a starting point in our investigations. In the course of our tests a number of modifications of the original method were found to be desirable so that, by an evolutionary procedure, a method of small scale

Jan 1, 1947

By William Greenawalt

The Greenawalt electrolytic copper extraction process is applicable to suitable oxide ores, sulfide ores and concentrates, and low-grade matte. The process is self-sustaining in acid on sulfide ores or concentrates, on mixed ores, on high-grade oxidized ores; and on low-grade oxidized ores the amount of acid to be purchased or manufactured is greatly reduced. The ferric iron is under easy control, and copper may be effectively deposited from solutions of any acid or iron content likely to be used in copper leaching. From 60 to 75 per cent. of the copper may be removed from the solution in passing through the electrolytic department, before returning the solution to the ore. The amount of copper requiring chemical precipitation, from the waste and foul solutions, is only about 5.0 per cent, of the total copper produced, and this 5.0 per cent. is converted into the electrolytic metal in the regular operation of the process. The entire process can be made practically automatic, and can be carried out mechanically. There is no uncertain departure of any kind in the application of the process; no unusual or unproved apparatus is used. EVER since electrolytic copper refining gave promise of success, about a half century ago, efforts have been made to apply the idea to the extraction of copper from its ores. The methods of attack have, usually, been to leach with a dilute acid and then to deposit electrolytically the copper from the resulting solution with the simultaneous regeneration of the solvent used in the process. Many efforts have been made, and many patents have been taken out, both in the United States and abroad, to give this idea practical application, but only within the past few years have the difficulties been surmounted. Leaching and electrolysis, as applied to copper ores, are among the most promising fields in modern metallurgy. New conditions are arising, which will bring the wet methods into prominence; while high freight rates and increasing cost of fuel will tend to limit smelting to highly favored localities. The possibilities offered by the installation of hydro-electric plants and the greatly enlarged range of power transmission will greatly widen the field of electrolytic methods.

Jan 1, 1924

By J. M. McDowell, E. C. Doty, F. Morgan

Improvements in the X-ray method of measuring liquid saturation and saturation distribution are presented. Two identical direct current amplifiers have been added to measure continuously the intensities of the X-ray tube output and the beam which has passed through the core under test. The ratio of these intensities is automatically recorded on a modified Brown Electronik Recorder. Arrangements have been made to drive the core automatically and in synchronism with the recorder chart so as to give a continuous curve showing the variation of liquid saturation along the length of the core. By determining the ratio of the two X-ray beam intensities simultaneously the measurements are made essentially independent of small fluctuation in voltage and current supplied to the tube. This improved technique has been used for investigating the fluid distribution along the length of cores and core assemblies when one fluid is displaced by another. Typical results of these studies are shown. INTRODUCTION In a previous publication' a method was described for measuring the oil saturation in cores which was based on the absorption of X-rays by the fluid content of the core. While that technique is capable of yielding accurate results, the original apparatus was not especially convenient for determining the fluid distribution along the length of a core. This was primarily due to the slow response of the amplifier and galvanometer and the necessity of making a point by point survey of the material under investigation. It was, therefore, not only possible for sections of the core having a variable or unusual saturation distribution to escape observation entirely, but changes in output of the X-ray generator between readings on the unknown and the monitor introduced errors in the measurements that could be avoided only by further stabilization of the source or by taking a large number of readings. This paper describes a method and apparatus for recording continuously and automatically the intensity of the X-ray beam that is transmitted by a core. The variation of saturation with time at a given section of the core may thus be found, or by scanning the core by driving it in synchronism with the recorder the saturation distribution may readily be determined. As indicated in the previous paper, the X-ray method possesses an advantage over the weighing technique in relative permeability experimentation in that the core need not be removed from the holder for the purpose of making a saturation measurement. Furthermore, the actual distribution of fluid and the effects upon that distribution of inflow and outflow heads may be investigated. And errors due to gas bubbles or loss of liquid that are frequently sources of error in volumetric methods of saturation determination are avoided. PRINCIPLE OF THE METHOD The energy in an X-ray beam that has passed through an absorbing material is expressed by the well known formula: E = E0, e-cd (1) where E, is the energy in the incident beam, µ the mass absorption coefficient, c the density or concentration of absorbing material, and d is the length of path of the beam in the absorber. The coefficient µ varies with the wavelength of the radiation as well as with the absorbing material. The output of an X-ray tube varies in an approximately linear manner with the tube current, but to the second or higher power of the anode voltage. Moreover, the quality or wavelength distribution of the radiation varies with the voltage.

Jan 1, 1950

By Thomas Egleston

The ores of mercury of North California are composed of metallic mercury and cinnabar. They are found in serpentine, and are very often associated with chalcedony, in masses more or less irregular, often concentrated enough, however, to furnish ores yielding from three to ten per cent., and sometimes richer. This deposit makes its appearance in Vallejo where it has been worked. North of here the mines are more developed. Most of the quicksilver mines, however, are situated in Sonoma and Napa Counties. On its outcrop the serpentine rocks have become decomposed, and have often been washed away to a considerable depth, so that in many cases in their neighborhood, what is apparently nothing but ordinary dirt, will frequently contain from two to three per cent. of metallic mercury, with but a trace of cinnabar, in which case, as at the Sonoma mine, it is made up into adobes and distilled. Such material does not require to be mixed with dirt to be made into adobes. Very often, also, the outcrop of the rock, where it is not decomposed, is filled with metallic mercury, so that by striking a pick into it, as at the Rattlesnake mine, a pound or more of mercury at a time will sometimes spurt out. Such rock as this is found in several localities in every stage of impregnation, and usually makes very rich ore. There is generally, however, very little of it, and it is found only in the first workings; the ore in depth is always cinnabar. At the Rattlesnake mine near Pine Flat, where large quantities of metallic mercury are found, the rock contains so much petroleum that it has been necessary to make special arrangements to burn the carbides of hydrogen, since the distillation of the petroleum causes an extra quantity of poor soot to be formed in the condensation-chambers. At the Geysers the ore is associated with large quantities of sulphur and gypsum, so that in a hand specimen there is often more sulphur than cinnabar, which is a serious impediment to working, especially for the modern style of furnace with iron condensers, and causes so much soot to be formed that it has been known to penetrate as far as the blower, and to so completely clog it as to prevent its revolution. The ore coming from the mine is more or less hand-picked. In one or two cases attempts have been made to treat the poorest, and especially the very fine ores, mechanically as at the California works.

By Arthur Taggart

FLOTATION of ores is a practical utilization of the energy that resides in the surfaces of solids and liquids. The best known manifestation of this energy is called surface tension; an equally important, though less apparent, phenomenon is adsorption. This paper reviews some of the recent investigations of these phenomena, and gives the results of certain experiments performed by the authors. Surface tension is a manifestation of energy having its seat at the bounding surface between the adjacent phases of a multiphase system. Thus, at the interface between a liquid and a gas, or between two immiscible liquids, or between a solid and a gas or a liquid, there are forces capable of doing work, their magnitude depending on the nature of the adjacent phases and the extent of the bounding area. These surface forces are inappreciable when the ratio of surface to volume of the adjacent phases is small, but they become powerful when this ratio becomes large, as it does when one of the phases is highly dispersed. Froth flotation, which consists in buoying solids heavier than water to the surface of water by means of gas bubbles, utilizes the force of surface tension to attach the solid particles to the gas bubbles and again to maintain the floating mass of bubbles as a more or less persistent froth at the surface of a pulp for a sufficiently long time to allow its removal. It follows from the second law of thermodynamics that the potential energy of a system in equilibrium is a minimum. Therefore a multiphase system, tending toward equilibrium, will arrange itself in such a way that the total energy of the interfaces will be the least possible. This end can be accomplished in two ways: by a change in shape that will reduce the interfacial area; by a change in the nature of the surface layer in

Jan 8, 1922

By Frank Corwin

It is the purpose of this article to give a brief account. of the experimental work and to show how the increase in efficiency was brought about. Part of the experimental work described in this paper was carried out by the writers, while in the employ of the Anaconda Copper Mining Co., under the direction of M. W. Krejci, Metallurgist, and Arthur Crowfoot, Chief Sampler. Complete records of all of the MacDougall testing work have been placed at our disposal through the courtesy of A. E. Wheeler, Superintendent. II. BRIEF HISTORY OF PRESENT MACDOUGALL PLANT. The first change from the Brueckner cylinders used for roasting concentrates at Great Falls was the construction of a MacDougall roaster of the Herreshoff type. This furnace was first started on June 15, 1898. It bad eight hearths, was lined with fire brick, and had an air-cooled central shaft, but no provision was made for cooling the rabble arms. It was operated for a while, and accomplished the work of roasting, but ran so hot that the rabble arms became twisted and distorted out of shape. To prevent the furnace from becoming too hot a device was then installed to draw the heated gases away from the hearths. This consisted of a pipe connected to alternate hearths of the MacDougall furnace and also connected to the flue. It was equipped with dampers, 'so that the hot gases could be drawn away from any one of the alternate hearths directly into the flue.

Jan 7, 1913

By Arthur West

IT is the purpose of this paper to describe briefly some recent large power stations for blast furnaces, where the blast is exclusively supplied by gas engines using furnace gas. The stations are given in the chronological order in which they were designed, in order to indicate the various improvements suggested by experience. Fig. 1 shows the blowing-engine station of the Bethlehem Steel Co. at Bethlehem. Although the picture shows only five blowing engines, the house now contains 11 engines. In the diagrammatic. plan the arrow shows the position and direction of camera. This station handles five modern blast furnaces of 450 to 500 tons capacity each. In this, as in all the other stations described in this paper, each furnace is blown by-two single tandem gas engines. Ten engines are thus required for five furnaces, leaving one single tandem spare engine. This spare capacity has been shown by several years' experience at Bethlehem to be adequate to insure continuous operation. The engines in the Bethlehem station are right hand and left hand, arranged in pairs. The outboard bearings of each pair are close together so that there is not room for passageway between them. On the right of the picture are shown the inclined drums communicating with the cold-blast lines outside of building, so that any engine may be operated on any furnace. The illustration shows four cold-blast gate valves with pipes passing through wall, but since the photograph was taken the drums have been extended to take care of a fifth valve for a fifth furnace. At the extreme back of the picture can be seen the tubs of three twin vertical-horizontal Southwark steam blowing engines, which, although of modern design and as good as new, are not operated because of the greatly reduced blowing cost shown by the gas blowing engines.

Jan 6, 1915

By William Fink

THE constitution of the aluminum-cobalt alloys has been the subject of relatively few investigations. Brunck1 analyzed the residue which remained after treating the 17 per cent cobalt alloy with dilute hydrochloric acid. The results of the analyses indicated the existence of a compound Co3Al13. Guillet2 published a liquidus for the aluminum-cobalt system which contained two maxima corresponding to CoAl6 and CoAl2 and two eutectic points at 30 and 74 per cent Co. The most extensive investigation of the system was carried out by Gwyer,3 whose results are summarized in Fig. 1. It will be noted that at the aluminum end there is a suppressed eutectic at 644° C. By extrapolation of the duration of the eutectic arrest to zero, the composition of the compound was placed at Co3Al13. Another thermal arrest was noted at 550° C., which Gwyer attributed to a peritectic reaction. The present investigation of the aluminum end of the aluminum-cobalt system is the eleventh of a series dealing with the constitution of aluminum; rich alloys prepared from electrolytically refined aluminum.4 Preparation of Alloys.-The alloys used in this work were all prepared from electrolytically refined aluminum, the analysis of which is shown in Table 1. In preparing some of the alloys, metallic cobalt (98 to 99 per cent) was used either directly or in the form of an intermediate alloy, the composition of which is given in Table 1. In order to obtain alloys of higher purity, cobalt was introduced into some of the alloys by means of chemically pure cobaltous chloride which was readily reduced by the aluminum. A small electric furnace with nickel-chromium heating elements was used in the preparation of the alloys.

Jan 1, 1932

By Nathan C. Rockwood

LIME is a very general term applied to products of limestone, in popular treatises often incorrectly, including ground or pulverized limestone used in agriculture. When used without qualifying adjective, the term usually means burned or calcined limestone, or quicklime, or calcia. The corresponding calcined product of magnesite is magnesia. If the calcined rock is relatively pure calcium carbonate, the resulting lime is a "high-calcium" lime; if the rock is dolomite, or a combination of calcium and magnesium carbonates, the lime is a "dolomitic" or a "high- magnesium" lime. There are various grades in between, depending on the percentage of magnesium carbonate and other ingredients in the raw rock. For some industrial purposes only high-calcium limes are suitable; in other processing-as, for example, neutralizing acid wastes -the relative percentages of magnesium and calcium carbonates in the raw material are not important. Limestone is burned (roasted or calcined) in furnaces known as lime kilns by direct exposure to the hot gases and flames. When heated to incandescence, the carbon dioxide content of the rock is expelled, leaving calcium and magnesium oxides, according to the formula usually written: [ ] This thermal reaction is reversible, which requires that the lime be withdrawn from the "calcining zone" of the kiln about as fast as made. Pure calcium carbonate would lose 44 pct of its weight in the calcining process; dolomite, 48 pct. Generally, the lime will retain the approximate size and shape of the piece of rock from which it is made but some few limestones tend to break down into granules or dust. Hence lime (quicklime) comes from the kilns in lumps or granules and normally is packed in water- tight containers in these forms, or is pulverized after calcination.

Jan 1, 1949

By Robert N. McIndoo, M. G. Woodle

10.5-1. Introduction. In the not-too-distant past, maintenance and the facilities for maintenance were considered a necessary evil to be given only secondary consideration in the development and planning of a surface mine operation. With the increasing sophistication of mining equipment and machinery, this concept has been replaced; and today's mine managers recognize that planning for adequate maintenance facilities is as important to a successful operation as a sound mining plan. This chapter will present the basic maintenance facilities and the fundamental considerations necessary to meet the varied requirements of surface mining. 10.5-2. Determination of Shop Facilities. The size, shape, and extent of maintenance facilities are contingent on the general mining plan, the location relative to outside facilities, and to the available capital. The type of construction employed is dependent on climatic conditions and preference. HAULAGE SYSTEMS. The type of haulage equipment used will dictate the kind of shops needed. Truck haulage requires entirely different facilities than rail haulage. Some mines will employ both systems, and can include hoists, skips, or conveyor belts in combination with locomotives or trucks. The requirements of each type will be discussed. MAINTENANCE ORGANIZATION. The pre-planning decision as to centralized maintenance vs. area maintenance, or a combination of both, will greatly affect the maintenance facilities required. A single pit with relatively short travel from shops to pit will probably have a centralized maintenance system. Where more than one mine is involved, or where there are diversified sections or functions in a mine (mine equipment, mill, conveyor, or

Jan 1, 1968