Search Documents

By Carl R. Christiansen, James J. Scott

Advance mine planning, coupled with good mining practice, can be employed to develop underground space in stone mines for future industrial usage. To assure the developer the maximum return on his investment, initial planning should consider all aspects of the commercial operation, including surface layout, mining, and underground industrialization. The modular concept of mining to compartmentalize the space offers several advantages over conventional methods. Some expenditures can be considered as mining costs with a reduction of profit from stone production while lowering the capital requirements for conversion for usable space.

Jan 1, 1977

By Sanford Belden

My topic, Recent Developments in the Design of Electric Mine Locomotives and Mining Machinery, does not require me to go into a general review of electricity as applied to the mining industry. Interesting as that subject always is, what I might say in regard to it, by way of introduction, would be unnecessary use of your time, since such facts are familiar to all. First, we will consider the recent development of the electric mine locomotive. We may well pause for a moment to reflect upon its importance to the coal-mining industry of to-day. With the dawn of the electrical age its advent was inevitable. Our practical interest is aroused not so much by the first crude effort as by the great efficiency attained during the 30 or more years since the electric locomotive made its first appearance. To judge accurately what it means to coal mining, and through coal mining to the industrial field at large, we would have to know how many of these locomotives are in use throughout the country and their aggregate daily performance, and then compare the results with what could be expected with other forms of power. Such data are lacking, but it requires no statistician to make it evident that the electric mining machine is a tremendous factor in modern progress, and that without it the work of the world could never have reached its present magnitude. Not only has the electric mine locomotive served its own special branch of usefulness, but incidentally it has solved in the main the whole problem of electric transportation. It is but a step from the triumph of a 25-ton locomotive leading a long train of loaded coal cars from a mine to the electrification of common carriers. We may or may not be near any great change in this respect. Economical reasons may hold it back for an indefinite period. But the fact remains that in the development of our mine locomotives we have met this larger emergency, in mechanical type and efficiency, whenever it may come.

Jan 6, 1914

By W. Chubb

By measuring the hardness of metals at temperatures just above and just below their allotropic change point, it has been established that crystal structure has a real effect upon the strength of metals. The DPH of cobalt, iron, titanium, uranium, and zirconium have been measured at temperatures up to 1000°C. It was found that the body-centered-cubic crystal structure is always the softer structure when it is involved in an allotropic transformation. The close-packed and more complex structures are inherently harder, and may be expected, therefore, to be better base materials for high strength alloys. IT has been observed that for metals with nearly the same melting point (i.e., tin and lead, magnesium and aluminum) the metal with the more complex crystal structure has a higher tensile strength and hardness. It might be asked whether this effect is really caused by the difference in crystal structure; and, if so, just what is the contribution of crystal structure to the strength of these metals. A qualitative answer to these questions can be obtained by measuring the change in hardness produced by the change in structure in metals exhibiting allotropic forms. The evidence for changes in mechanical properties during allotropic transformations is rather meager. In 1909, Rosenhain and Humfrey' observed that "ß" iron showed much less deformation at the transformation temperature than a iron. By means of a torsion test, Lee found that iron bars were "critically plastic" at the a-7 transformation temperature. Sauerwald and Knehans have shown that the dynamic hardness of iron increases between 900" and 1000°C. In 1930, Albert Sauveur' presented data on the hardness, tensile strength, and torsional strength of pui-e iron up to 1000°C. He concluded, "At 900°C, the a iron transforms into y iron, and this is accompanied by increased strength and stiffness and decreased ductility." The same year, Schischokin" obtained data on the hardness of thallium at temperatures above and below its transformation temperature. His data are replotted on semilogarithmic coordinates as Fig. 1. The fact that his data fall on straight lines in this type of plot is believed to attest to the purity of his metal and the accuracy of his results. In 1941, Nadai and Manjoine" obtained tensile data on pure iron with an indicated increase in strength at about 900°C. These experiments make it quite evident that changes in mechanical properties occur when a metal transforms from one crystal structure to another; but, except for Schischokin's data on thallium, none of the measurements seem accurate enough to determine the relative magnitude of the mechanical property change. Materials The metals that have been examined for changes in hardness during transformation include l—as- deposited commercial electrolytic cobalt about 99.7 pct pure, 2—Armco ingot iron, 3—are-melted iodide titanium of a purity in excess of 99.8 pct, 4—uranium of a purity in excess of 99.5 pct, 5—are-melted iodide zirconium of a purity in excess of 99.8 pct, 6—annealed, 0.08 pct C, rimmed steel, and 7—commercially pure RC55 titanium. While the purity of the first five of these materials leaves something to be desired, it will be noted that the observed hardness discontinuities occurred at the accepted transformation temperatures. (These temperatures are indicated by vertical arrows in Figs. 1 and 3 through 7.) The last two materials are commercial alloys introduced to show the effect of minor alloying elements upon the hot hardness curve. Apparatus Hardnesses at elevated temperatures were determined by means of a vacuum hot hardness machine. A diagram showing the basic features of this machine appears as Fig. 2. This machine is essentially a deadweight hardness .machine in a furnace within a vacuum chamber. The sapphire-tipped indentor

Jan 1, 1956

By Gust Bitsianes, Joseph H. M. Beaty

Successful blast-furnace operation depends upon securing an optimum balance between a number of important variables. This balance will vary somewhat from furnace to furnace in the same plant and with raw materials available in different plants. It is difficult to isolate the effect of any one variable unless it has a rather pronounced effect upon the efficiency of operation. The physical properties of iron ore and coke are known to affect the process, yet it is difficult to set up any definite yardstick by which these differences can be appraised. In recent years, whenever practicable, operators have taken steps to obtain better control over the absolute size and uniformity of size of the ore and coke. The size and physical character of the stone, however, have received comparatively little attention, emphasis being placed upon chemical composition, fluxing efficiency, and action as a desulphurizing agent. Since the stone occupies only about 10 per cent of the volume of the stock column, its influence upon permeability is less than that of the ore and the coke. The large pieces now used have a tendency to roll to the center and thus increase the permeability of this part of the stock column. Smaller pieces would be more effective in promoting the permeability of denser portions of the stock. The size and physical properties of blastfurnace stone are important also for reasons best understood by considering the results obtained by the crushing and the sizing of iron ore. Crushing ore to about 2 in. at Provo, Utah, and to about I in. in Alabama produced material somewhat less permeable to gases, even though sized. In spite of some sacrifice in permeability, the efficiency of the process was improved by crushing and sizing the ore, as indicated by a substantial saving in fuel and increased output. This saving in fuel is due in large measure to more thorough reduction of ore in the upper part of the furnace and to a corresponding decrease in the amount of carbon consumed prematurely above the tuyeres by the reaction CO2 + C = 2CO - 70,080 B.t.u. [I] The physical properties of stone, its size and rate of calcination are important because they influence the rate at which CO2 is released and the completeness of calcination before reaching a level in the furnace where the temperature does not exceed 1050°C. (1920°F.). Briefly, carbon dioxide from the limestone or from the reduction of ore may cause premature corn bustion of carbon above the tuyeres. Assuming that 1000 Ib. of limestone is used per ton of pig iron, about 435 Ib. of CO2 will be liberated during calcination of a good grade of stone. If all this CO2 from the stone were to oxidize carbon prematurely, about 120 lb, would be consumed above the tuyeres in a heat-absorbing reaction. The amount of carbon thus consumed when a

Jan 1, 1943

By Joseph H. M. Beaty, Gust Bitsianes

Successful blast-furnace operation depends upon securing an optimum balance between a number of important variables. This balance will vary somewhat from furnace to furnace in the same plant and with raw materials available in different plants. It is difficult to isolate the effect of any one variable unless it has a rather pronounced effect upon the efficiency of operation. The physical properties of iron ore and coke are known to affect the process, yet it is difficult to set up any definite yardstick by which these differences can be appraised. In recent years, whenever practicable, operators have taken steps to obtain better control over the absolute size and uniformity of size of the ore and coke. The size and physical character of the stone, however, have received comparatively little attention, emphasis being placed upon chemical composition, fluxing efficiency, and action as a desulphurizing agent. Since the stone occupies only about 10 per cent of the volume of the stock column, its influence upon permeability is less than that of the ore and the coke. The large pieces now used have a tendency to roll to the center and thus increase the permeability of this part of the stock column. Smaller pieces would be more effective in promoting the permeability of denser portions of the stock. The size and physical properties of blastfurnace stone are important also for reasons best understood by considering the results obtained by the crushing and the sizing of iron ore. Crushing ore to about 2 in. at Provo, Utah, and to about I in. in Alabama produced material somewhat less permeable to gases, even though sized. In spite of some sacrifice in permeability, the efficiency of the process was improved by crushing and sizing the ore, as indicated by a substantial saving in fuel and increased output. This saving in fuel is due in large measure to more thorough reduction of ore in the upper part of the furnace and to a corresponding decrease in the amount of carbon consumed prematurely above the tuyeres by the reaction CO2 + C = 2CO - 70,080 B.t.u. [I] The physical properties of stone, its size and rate of calcination are important because they influence the rate at which CO2 is released and the completeness of calcination before reaching a level in the furnace where the temperature does not exceed 1050°C. (1920°F.). Briefly, carbon dioxide from the limestone or from the reduction of ore may cause premature corn bustion of carbon above the tuyeres. Assuming that 1000 Ib. of limestone is used per ton of pig iron, about 435 Ib. of CO2 will be liberated during calcination of a good grade of stone. If all this CO2 from the stone were to oxidize carbon prematurely, about 120 lb, would be consumed above the tuyeres in a heat-absorbing reaction. The amount of carbon thus consumed when a

Jan 1, 1943

By Nathaniel Arbiter

THE separation of minerals by flotation can be regarded as a rate process, with the extraction of any one mineral determined by its flotation rate, and the grade of concentrate by the relative rates for all the minerals. So regarded, the significant variables for the process are those that control the rates. These variables are of two types, the first describing the ore and its physical and chemical treatment prior to flotation and the second characterizing the separation process in the cells. This paper will examine the variation in rates for a group of separations, will show that a simple rate law appears to govern, and will consider the relation of the control variables to the rates. The use of rate constants for evaluation of performance and efficiency will be discussed.

Jan 9, 1951

INTERNATIONAL GEOLOGICAL CONGRESS. (For further particulars apply to the Secretary, 12th International Geological Congress, Victoria Memorial Museum, Ottawa, Canada ; cable address, Geocong, Ottawa.) The Coal Resources of the World.-Three quarto volumes of about 400 pages each, 8 1/4 by 10 3/4 in., and an atlas of about 70 maps in colors, 13 1/3 by 19 1/2 in., bound in heavy paper cover. Edition limited to 3,000 copies, One thousand copies will be reserved for members of the International Geological Congress, and the remainder of the edition will be distributed in the order in which applications are received. Price, $35 per set. Ready in July, 1913. This book is an inquiry made upon the initiative of the Executive Committee of the Twelfth International Geological Congress, with the assistance of geological surveys and mining geologists of different countries, published by: Morang & Co., Ltd., Toronto, Canada. Headquarters During Session at Toronto. The headquarters will be a t the University of Toronto, where there will be a branch post-office open at all hours and at which registered mail may be received or despatched, money orders sent or cashed, etc. A hank will be established at which money may be exchanged. A typewriting service will be maintained, also a telephone service and messenger service. Railway and steamship agents will also be in attendance. A restaurant service providing luncheon in the middle of the day will be arranged.

Jan 8, 1913

By W. M. Rust, W. D. Mounce

THE almost universal acceptance of electrical logging by the petroleum industry calls for a critical examination of the physical bases of the common methods. This is particularly needed for the natural potential log. The conventional explanations are based on the phenomena of electrofiltration and electro-osmosis. However, experimental data show that they fail to give a basis that is quantitatively sound. Moreover, they lead to interpretations of details of electrical logs that are erroneous. It was found experimentally that when a plug of shale is placed in a chain of dissimilar electrolytes, a current flow results. Experiments on oil-well cores and fluids similar to those existing in wells show that potentials are set up which are in reasonable agreement with those encountered in electrical logging. Doubt- less other sources of potential are important but this explanation not only accounts for much of the potential but also clarifies some fairly familiar examples of misinterpretations.

Jan 1, 1944

By R. W. Diamond

THREE mills are now operated by the Consolidated Mining & Smelting Co. of Canada, Ltd.: (1) The Sullivan Concentrator, Chapman Camp, B. C. (near Kimberley, B. C.), (2) the, St. Eugene Concentrator, Moyie, B. C., and (3) the. Tadanac (Customs) Concentrator,Trail, B. C. Differential flotation is the only concentration method employed in all three plants. Tables are used for pilot work only. Values in all ores treated are as minerals of some or all of the metals -lead, zinc, gold or silver. Occasional customs ores contain small amounts of copper. Sulfide iron content of ores treated varies from a FIG. 1.-THE SULLIVAN CONCENTRATOR, CHAPMAN CAMP, B. C. (NEAR KIMBERLEY, B. C.). low figure in some ores to 38 per cent. iron in Sullivan ore. Gangue minerals vary considerably. A few customs ores are somewhat oxidized and as a result present difficulties. Flotation equipment and control are similar in the three mills, and the flow sheets at the St. Eugene and Tadanac mills, while much simpler, are modeled after that of the Sullivan Concentrator. In this paper I will not detail treatment nor equipment in any of our plants but will describe special features in, or in connection with, all of them. I will then deal with flotation reagents, describing our use of each of them, particularly where differing from general practice. I will conclude with comments on special subjects related to differential-flotation.

Jan 1, 1927

By R. F. Hollis, C. K. McArthur

PRIOR to the application of anion exchange, all recovery of uranium from acid leach liquors precipitated an impure product requiring further upgrading before it could be refined. The ion exchange process, on the other hand, provides excellent selectivity for extracting soluble uranium from leach liquors, so that high grade concentrates can be produced directly. The discovery that uranium is readily adsorbed by anion exchange resins, together with the experience of resin and equipment manufacturers in water treatment, led to rapid development of ion exchange in a multiple column operation. Many processing plants using fixed bed ion exchange are in operation or under construction in Africa, Australia, and Canada. There are a limited number in the U. S. Although the fixed bed process has been highly successful, the feed to the ion exchange columns must be a clear solution, which is obtained by filtration or by countercurrent decantation of leached pulps. With some ores, poor filtration or settling characteristics make production of a clear solution difficult. Most processing plants in the U. S. receive their ores from a number of small mines, and there is considerable variation in the settling and filtering behavior of the ores. An ion exchange process was therefore desirable in which the uranium could be recovered directly for the leached pulp by adding ion exchange resin, which could be then separated from the pulp by a screening operation. The process would thus resemble the cyanide-charcoal process in which gold is adsorbed from cyanide pulp by means of activated charcoal. Preliminary tests in which leached pulps were directly contacted with resin beads led to the development of the RIP process.

Jan 4, 1957

By J. H. Westbrook

UNTIL very recently the development of high temperature alloys has been strictly empirical. It is, in fact, a great tribute to the intuition, perseverance, and industry of the practicing metallurgists of this country and abroad that the amazing increases in gas turbine service temperature over the past 15 years have been achieved with so little fundamental knowledge. The result of this development has been the realization of successful but highly complex alloys possessing five, six, or more alloying elements and correspondingly complex microstructures. Within the last few years, considerable effort has been devoted to the identification of the secondary phases in these alloys and to the correlation of the presence or absence of such phases with alloy properties. Little attention, however, has been given the problem of identification of the mechanism (s) by which such phases enhance the properties of the alloy and especially to the assessment of the particular properties of the secondary phase (either in- trinsic or relative to the matrix phase) which are basically responsible for the improvement. Conceivable mechanisms which might apply include dispersion hardening and precipitation hardening. In both cases geometrical factors—particle size, dispersion, volume fraction, etc.—and agglomeration re-

Jan 1, 1958

By Norman B. Pilling, George P. Halliwell

The effects of lead and tin up to maximum contents of about 0.1 per cent. each, in the presence of oxygen between 0.04 and 0.30 per cent., have been studied. Tin is retained efficiently in the oxidized condition, whereas lead is not. An approximate relation between the lead-oxygen and tin-oxygen contents is deduced which, if observed, permits the presence of these elements without detrimental effect. Excess of lead beyond this limit affects ductility and rolling properties adversely and an excess of tin correspondingly diminishes the conductivity. It is shown that copper carrying a combined lead and tin content of several hundredths per cent., yet fully equal in quality to electrolytic wirebar, may be produced under commercial conditions. Tin is not normally found in more than bare traces in current grades of American electrolytic copper, and lead is rarely found to more than a few thousandths per cent. In the electrolytic refining of copper these metals do not present great difficulty in separation and their presence in any considerable amount in copper that has been refined by this method need not be tolerated. On the other hand, the effect of these elements is not entirely academic, as a considerable tonnage of scrap copper liberally contaminated with them has been reclaimed by the fire-refining process into metal with a residual lead and tin content of several hundredths per cent., yet having excellent working properties and fully equal in quality to current grades of electrolytic wirebar. Such copper has been found entirely suitable for use in the manufacture of electrical apparatus. In the absence of oxygen, tin is known to depress the conductivity rapidly, and lead to impair ductility and the rolling properties, yet the effects of these metals on commercial grades of copper—i. e., copper containing from 0.03 to 0.10 per cent. of oxygen—apparently has not received systematic attention. Occasional reference is made to the fact that in the presence of oxygen lead may be tolerated, yet Addicks says,1 in regard to overpoling: "The unstable condition can be controlled by adding certain substances, notably lead, in small quantities, but as mere

Jan 1, 1926

By W. Philippoff

ALTHOUGH Gaudin1 and more recently Sutherland2 have calculated the probability of collision of a falling mineral particle with a rising bubble, there is no published information concerning the details of the mechanism of attachment of a collector-coated particle to a bubble. During the past year the writer has developed a theory for the mechanism of attachment, which has been substantiated experimentally. Funds for the investigation and for some of the equipment used have been supplied by the Mines Experiment Station of the University of Minnesota. Motion picture studies of the phenomena involved in the collision between mineral particles and bubbles, such as those of Spedden and Hannan," show that the contact can be completed within 0.3 millisec. Formulas developed for rigid bodies have hitherto been used' for the calculation of the motion of bubble and particle, but it is obvious that a bubble cannot be regarded as a rigid body. On the contrary, Spedden and Hannan's pictures show a great degree of deformation during the collision. The time of attachment was calculated as the time the particle drifted past the bubble. Time of Collision The theory presented in this paper enables calculation of the time of collision, using the concept that the bubble, or more generally, a liquid-air interface, acts as an elastic body. The elasticity, defined as the restoring force on a mechanical deformation, is caused by the surface tension and is the result of the principle of the minimum of free surface energy. It is well known that an elasticity together with a mass determines a frequency of vibration. The vibrations of jets and drops caused by the elasticity of the interface are known to comply exactly with the classical theory of capillarity.' However, the vibrations of isolated bubbles, as distinct from foams, have not been investigated previously. The following equation, presented elsewhere,' has been deduced for these frequencies: 3_____________________ fB = 9.20.vV.vn. (n-1).(n+2)/8 [I] in which fB is the frequency of a harmonic of the bubble in cycles per second, V the volume of the bubble in cc, n a number determining the order of the harmonic, and n = 2 the basic vibration. The first (basic) harmonic describes a change of the spherical bubble to an ellipsoidal bubble. The higher harmonics are more complicated, for the circumference of the bubble is divided approximately into as many parts as the order of the harmonic. As an example, Spedden and Hannan's published motion picture of a vibrating bubble corresponds to the sixth harmonic. Eq 1 shows that only the first and third harmonics are simple multiples (1 and 3), all the others being irrational fractions of the basic frequency. This means that the shape of the vibration can change with time and is in general unsym-metric in respect to the time axis. Such conditions prevail when there is a distributed elasticity or mass, as in the case of vibrating membranes or rods. The constant 9.20 is valid for water at room temperature, but a general solution involving the physical constants of the liquid has not been found. The case of the floating particle is much easier to treat than that of the bubble. It can be assumed that the elasticity is caused exclusively by the interface and that the mass is concentrated in the particle together with some adhering water. The following expression for the frequency of a system of one degree of freedom can be applied: fP = -1/2-vE/m [2] Here fp is the frequency of the particle vibration in cycles per second, E the elasticity in dynes per cm, and m the mass in grams. The classical theory of impact phenomena gives the time of collision during the striking of a spring (in this case the surface of the bubble) by a mass, as: t, = 2/f = nvm/E [3] It is now possible to develop an expression for the elasticity of a floating cylindrical particle. The force equilibrium of a cylinder floating end on at the air-liquid interface is given by the well-known equation (Poisson7 1831) P = /4 D2-pL-g-h + D.y sin a [4] which accounts for the buoyancy and the action of the surface tension where P is the force acting on the particle in dynes (weight-buoyancy), D the diameter of the cylinder in cm, PL the density of the liquid in grams per cc, g the acceleration of gravity = 981 cm per sec2, h the depression of the cylinder below the surface of the liquid in cm, y the surface tension in dynes per cm and a the supporting angles or the one required to insure equilibrium, a being smaller than the contact angle 0. Although demonstrated by Poisson, it has not

Jan 1, 1953

By W. Philippoff

ALTHOUGH Gaudin1 and more recently Sutherland2 have calculated the probability of collision of a falling mineral particle with a rising bubble, there is no published information concerning the details of the mechanism of attachment of a collector-coated particle to a bubble. During the past year the writer has developed a theory for the mechanism of attachment, which has been substantiated experimentally. Funds for the investigation and for some of the equipment used have been supplied by the Mines Experiment Station of the University of Minnesota. Motion picture studies of the phenomena involved in the collision between mineral particles and bubbles, such as those of Spedden and Hannan," show that the contact can be completed within 0.3 millisec. Formulas developed for rigid bodies have hitherto been used' for the calculation of the motion of bubble and particle, but it is obvious that a bubble cannot be regarded as a rigid body. On the contrary, Spedden and Hannan's pictures show a great degree of deformation during the collision. The time of attachment was calculated as the time the particle drifted past the bubble. Time of Collision The theory presented in this paper enables calculation of the time of collision, using the concept that the bubble, or more generally, a liquid-air interface, acts as an elastic body. The elasticity, defined as the restoring force on a mechanical deformation, is caused by the surface tension and is the result of the principle of the minimum of free surface energy. It is well known that an elasticity together with a mass determines a frequency of vibration. The vibrations of jets and drops caused by the elasticity of the interface are known to comply exactly with the classical theory of capillarity.' However, the vibrations of isolated bubbles, as distinct from foams, have not been investigated previously. The following equation, presented elsewhere,' has been deduced for these frequencies: 3_____________________ fB = 9.20.vV.vn. (n-1).(n+2)/8 [I] in which fB is the frequency of a harmonic of the bubble in cycles per second, V the volume of the bubble in cc, n a number determining the order of the harmonic, and n = 2 the basic vibration. The first (basic) harmonic describes a change of the spherical bubble to an ellipsoidal bubble. The higher harmonics are more complicated, for the circumference of the bubble is divided approximately into as many parts as the order of the harmonic. As an example, Spedden and Hannan's published motion picture of a vibrating bubble corresponds to the sixth harmonic. Eq 1 shows that only the first and third harmonics are simple multiples (1 and 3), all the others being irrational fractions of the basic frequency. This means that the shape of the vibration can change with time and is in general unsym-metric in respect to the time axis. Such conditions prevail when there is a distributed elasticity or mass, as in the case of vibrating membranes or rods. The constant 9.20 is valid for water at room temperature, but a general solution involving the physical constants of the liquid has not been found. The case of the floating particle is much easier to treat than that of the bubble. It can be assumed that the elasticity is caused exclusively by the interface and that the mass is concentrated in the particle together with some adhering water. The following expression for the frequency of a system of one degree of freedom can be applied: fP = -1/2-vE/m [2] Here fp is the frequency of the particle vibration in cycles per second, E the elasticity in dynes per cm, and m the mass in grams. The classical theory of impact phenomena gives the time of collision during the striking of a spring (in this case the surface of the bubble) by a mass, as: t, = 2/f = nvm/E [3] It is now possible to develop an expression for the elasticity of a floating cylindrical particle. The force equilibrium of a cylinder floating end on at the air-liquid interface is given by the well-known equation (Poisson7 1831) P = /4 D2-pL-g-h + D.y sin a [4] which accounts for the buoyancy and the action of the surface tension where P is the force acting on the particle in dynes (weight-buoyancy), D the diameter of the cylinder in cm, PL the density of the liquid in grams per cc, g the acceleration of gravity = 981 cm per sec2, h the depression of the cylinder below the surface of the liquid in cm, y the surface tension in dynes per cm and a the supporting angles or the one required to insure equilibrium, a being smaller than the contact angle 0. Although demonstrated by Poisson, it has not

Jan 1, 1953

By Thomas C. Wilder

The activities of both components and the partial and integral molar thermodynamic properties of mixing for the liquid Al-Ge system at 1200°K and for the gertnanium-rich Al-Ge liquidus have been determined from data for eighteen alloys of compositions in the range 0.0593 < 0.880 using the reuersible gal-vanic. cell in the temperature interval 9320 to 1258°K. The liqui-dus compositions above 93 2 °K loere also ve determined by observing the discontinuities in the C us T plots for the high-melting alloys. This system shows moderate negative deviation from ideality throughout, the values for y° being 0.212 and 0.189 for aluminum and germanium, respectively, at 1200°K. Pavtial molar Properties of aluminum on the germanium-rich solidus and at infinite dilution in Ge(s) oboue 932°K were estimated from the foregozng measurements and the equlibrium data of previous investzgators. RECENT compilations of data1" have shown an increasing demand for knowledge of the thermodynamic properties of mixing of metallic alloy systems. In the case of binary-liquid systems where one of the components is a semiconductor this information is useful because, primarily, properties of the second (dopant) component on the liquidus, solidus, and at infinite dilution may be determined more accurately than from calculations based on the phase diagram. In this investigation a reversible galvanic cell was used to determine the chemical potential of aluminum in the two-phase region, liquid + [Ge], on the germanium-rich side of the A1-Ge system in the temperature range 932" to 1193°K. In addition, similar measurements for homogeneous liquid A1-Ge alloys for the entire composition range were obtained for the temperature interval 932" to 1258°K. The cell used was: The experimental technique and the treatment of the data were essentially the same as described earlier394 and are elaborated upon only briefly here. Each cell consisted of a liquid aluminum anode and three A1-Ge alloy cathodes of different composition which were held in Morganite alumina crucibles. The alloys were made up from aluminum and germanium weighed to the nearest 0.1 mg to a total weight of 5 to 10 g. Aluminum was a gift of Aluminum Co. of America and had a purity of 99.995+ pct. Germanium of transistor grade was a gift of Bell Telephone Laboratories. The four electrodes were contained in a larger alumina crucible which also held the prepurified fused chloride electrolyte. Contact to the electrodes was made by tantalum wire leads sheathed in alumina. The tantalum leads were centered in the electrodes by suitable positioning of an alumina radiation shield which fitted on the top of the - alulnina crucible. Two chrome l-alumel thermocouples, sheathed in quartz wells, completed the internal cell arrangement. The entire assembly was enclosed in an alumina tube, fitted with a water-cooled copper head so the system could be evacuated and then flushed with purified argon. *

Jan 1, 1967

By M. B. Holt

At this time, when electricity in its various applications is attract- ing so much interest, and with such good reason, it has been suggested to me that, as the Aspen Mining and Smelting Company, of Aspen, Pitkin county, Colorado, was the first mining company in America to employ electrical power for hoisting, a record of what has been accomplished by this company would be of interest. Early in the year 1888 the question of power for the development of the ore-horizon lying below the level of the tunnel through which the property is worked, became one of importance. The conditions under which it was proposed to use power were as follows (See Fig. 1): The company&apos;s mines lie upon the northwestern slope of a mountain, the ascent of which is at an angle of 28&apos; from the horizon. The ore, consisting of argentiferous galena and other silver-bearing mineral, is found at or near the plane of contact of a superincumbent mass of blue limestone, with an underlying bed of dolomite. This contact plane dips north 30° west, at an angle of 60&apos; with the horizon. A tunnel 1000 feet in length, driven south into the mountain near

Jan 1, 1892

By Dwight K. Smith, Greg Carter

Studies have been conducted on The properties of many deep well cementing compositions to determine their Strength behavior over curing periods to 180 days at elevated tem-peratures and 3,000 psi pressure. This pressure results in essentially the .vat, compressive strength as that obtained with much higher pressures in ac-cordance with the findings of an API subcommittee &apos; These different compositions include API C1asses A, E, and F cements containig additives such as retarders, berrtorlite, heavy weight materials and pozzolans. All compositions except mixtures of Poz-zolrrrts and hydrated lime show from mild to severe degrees of strength lass over a temperature rang from -730 to 320" F after setting. Pozzolatl-time compositions actually gain in strength with time at these high temperatures. Other chemical find physical properties evaluated to observe their inter-relation.ship with Strength loss show very little correlation except in per-meability. As retrogression in strength increases, the permeability of set cement increases. X-ray difraction patterns on the set products indicate the formation of certain compounds having little or no strength value in those cementing compositions where strength loss was more severe. INTRODUCTION As a result of the growing trend toward deep well completions, a study has been made on the properties of the various cementing slurries presently in use at elevated temperatures and pressure. The strength of these compositions is of prime importance in selecting the most suitable material for use at high temperatures, to determine WOC time and the proper time to perforate with a minimum of shattering. Of primary interest in this investigation was the strength behavior of various compositions currently in use, and the effect of additives on cement after long periods of curing under severe conditions. Earlier investigators have pointed out that the strength of some cements will increase with increasing curing temperature to about 220 to 340" F, but at higher temperatures a loss in strength occurs at extended time intervals. Studies by the API Mid-Continent District Study Committee on Oil Well Cements&apos; outlined a testing procedure whereby field conditions of temperature and pressure could be simulated in the laboratory.&apos; It was observed that retarded cements undergo changes at elevated temperatures and some lose as much as 50 per cent of their early strength when cured at high temperatures. The scope of these tests was limited to curing periods of 1 to 28 days; additives were not covered in this study. Saunders and Walker&apos; found that the use of additives influenced the strength behavior of cements at high temperatures, but studies were conducted only to a seven-day curing period. Ludwig and Pence&apos; conducted an investigation of two types of cements under elevated pressures and temperatures in an effort to explain the causes of this loss in strength phenomenon. It was observed that with retrogression in strength there were other physical and chemical changes which took place as the cement aged. Today there are a number of cementing compositions available for use at well depths below 10,000 ft. Since all these earlier investigations were limited in curing time as well as the number and type of compositions studied, it was believed that a more extensive study should be conducted on the properties of cements at elevated temperatures, and this work should include those compositions actually in general field use at this time.

By Allan J. Clark

It is nearly three years since the metallurgy of the Homestake ore was discussed with considerable thoroughness, in a paper1 read before the Institution of .Mining and Metallurgy. Certain changes have been made in this period which are perhaps of sufficient interest to justify a brief description, and it is chiefly with such details and miscellanies that this paper will deal. In the circumstances, a certain amount of repetition is inevitable, but matter treated of in the former paper will be referred to here only when it is necessary for the sake of coherency. For full descriptions of equipment and technique, the former paper should be consulted. The mineralized slates and schists which constitute the ore vary considerably in composition, but the unoxidized ore, perhaps constituting the major part of the reserves, contains either chlorite or hornblende (cummingtonite), with quartz, carbonates of lime, magnesia and iron, and arsenopyrite, pyrite, and pyrrhotite. Ferrous minerals predominate, and this fact has been an important factor in determining the metallurgical treatment. With one or two exceptions the minerals noted are of relatively high specific gravity, and the ore as a whole is exceptionally heavy, many determinations giving an average specific gravity of 3.00. This high specific gravity presents one decided advantage, when the cost of treatment is compared with operations elsewhere, in that the ton, almost universally the basic unit, represents a volume probably less by 10 per cent. than that of many gold ores. On the other hand, this high gravity renders more difficult the discharge of pulp from mortars, its distribution on amalgam tables, and its transportation in launders. In the same way, as attesting the usual balance of such variations of different ores, it may be noted that the needle-like fibers of hornblende (cummingtonite), interlacing throughout the mass, render the ore more difficult to crush than would be anticipated, but on the other hand assist

Jan 1, 1916

By J. W. Snavely

WITH all the advantages of handling bulk materials by means of belt conveyor also go some problems, one of the most persistent being that of cleaning. When sticky materials are being carried; the build-up of material on the return idler rolls results in difficulty of belt training. Much attention has been given to the problem of cleaning conveyor belts, and a great variety of cleaning devices have been developed. Even the best involve troublesome maintenance, and none can completely remove the fine particles imbedded in the belt cover, which cause rapid wear of the return idler rolls, and at the same time, of the belt cover as well. One of the major rubber companies has been promoting a two-way belt system, in which the conveyor belt is given two successive 90" twists at each end to enable it to carry material in both directions simultaneously. For many years the flat belt transmission industry has installed quarter-turn and half-turn twists in countless numbers of instances. While quarter-turn and half-turn twists in transmission belts is a familiar application, the 180" twist apparently has never been previously attempted with a conveyor belt. About a year ago, two officials of the National Iron Co. of Duluth, Lester and Lewis Erickson, proposed twisting the return run of a conveyor belt on an installation that they were designing for one of the major iron ore producers. Since then the soundness of the idea has been demonstrated, both in theory and by practical test, with the result that the installation of two conveyor belts involving the twisting of the return run is now under way. These two installations are designed to have the return run of the conveyor belt twisted 180" as it leaves the snub pulley at the head drive. The clean underside of the belt is thus placed against the idlers on the return run as well as on the carrying run. Just before it enters the tail pulley, the belt will be twisted an additional 180°, restoring it to its normal position. Because this twisting of the return run of a conveyor belt is a radical departure from accepted practice, an elaborate and extensive test was conducted early in 1950 to demonstrate that this twisting of the return run could be done successfully, also to establish application data for accomplishing this twisting, and to determine if any special equipment would be required. In studying this concept of twisting the return run of a conveyor belt, a number of problems need to be solved, primarily the ones brought about by deliberately introducing an unequal distribution of stress across the conveyor belt and controlling that maldistribution of stress, while confining it to the return run portion. The tension conditions existing in the return run of a conveyor belt are clear to all designers. First, the return run carries the initial or slack side tension of the conveyor belt, the tension that must be supplied to the return run to provide proper frictional contact between the belt and the driving pulley so that the necessary power can be transmitted from the driving pulley to the belt without slippage. This slack side tension is supplied to the belt by means of takeups, either of the gravity type, which can be vertical or horizontal, or by means of the screw type. With inclined or declined belt conveyors the slope tension also must be considered, which is the tension imposed by the weight of the belt hanging from the top pulley. This slope tension frequently can furnish part or even all of the initial tension required. The maximum value of the slope tension will be at the top pulley, and it decreases in direct proportion to the length. In addition to the foregoing, it frequently is desirable to impose arbitrarily additional slack side tension to provide sufficient tension at the loading point at the tail, so that the belt will adequately support its load between the carrying idlers. Design Conditions for Twisting A number of design conditions exist, which must be satisfied successfully to accomplish the twisting of the return run without exceeding normal working limits in any portion of the conveyor belt. It is obvious that the belt edge, in its relation to the center of the belt, must stretch in making a twist, because as the twist is accomplished, the belt edge travels through a longer path than does the center of the belt. It is further obvious that if the edge of the belt is stretched, a redistribution of stress in the belt is required to allow this edge stretching. Moreover, this stress will be unequal across the width of the belt, having a maximum value at the edges, with a minimum value at the- center of the belt. With correct initial tension in the return run of a conveyor belt, the existing slack side tension will be unequally distributed when a twist is introduced. A condition then exists in which the edge stresses,

Jan 1, 1952

By Alwyn Birchmore Cox, Ian William Wark

In defending the chemical theory of flotation, Taggart, del Giudice and Ziehl have criticized1 the views of those who prefer to attribute the effects of certain flotation agents to adsorption. Perhaps with some justification, they describe the latter term as the "haven of refuge of writers lost in a morass of shaky experiment and muddy thinking." We prefer to regard it, however, as a haven of refuge for writers who seek a conventional term to describe the formation of films of flotation reagents on solid surfaces, because in many cases it is not yet possible to specify the forces that hold them there. Originally, as Taggart and his associates state, adsorption connoted a concentration difference and nothing more. In recent years, workers in the field of surface chemistry have tacitly added other meanings, and they now speak of orientated adsorption of unimolecular films on a solid sub-strate, of chemi-adsorption, and of exchange adsorption. Thus the term adsorption may connote simply the Gibbs layer of excess concentration at the surface of a solution, or a unimolecular film at the surface of a solid. Perhaps this has led to the misunderstanding of Taggart, del Giudice and Ziehl concerning the relationship between surface tension and adsorption at solid surfaces. The change in "surface tension" accompanying adsorption at a liquid surface can be used as a measure of the adsorption, and the Gibbs equation as quoted by these authors correlates these two conceptions. But, to correlate two conceptions docs not necessarily imply an attempt to explain either, although sometimes such an "explanation" is carelessly inferred. Use of "surface energy per unit area" instead of the numerically equal but more difficult and less definite conception of "surface tension per unit length " would lessen many of the present difficulties. (Compare with Adam.2) At interfaces involving a solid phase, neither &apos;" surface tension " nor " interfacial tension "can have any meaning, but the conception "interfacial energy per unit area" call be understood by anyone who is familiar with the concept of free energy. While it is true that surface energy cannot be directly measured at a solid surface,

Jan 1, 1939