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By Rossiter W. Raymond

The 12th of April, 1877, witnessed the celebration, at Freiberg, Saxony, of an event profoundly important for the ancient mining industry of that district, and full of interest to mining engineers throughout the world—namely, the connection of the famous Roth-

Jan 1, 1879

By R. J. Robbins

"For his exceptional ability both as an engineer and entrepreneur in the conception, design, and marketing of underground boring equipment; a technological development which has greatly improved the efficiency and safety of underground mining." Recipient of the 1984 D.C. Jackling Award

Jan 1, 1985

By Joseph Jensen

THE history of the normal oil field is supposed to show an oil graph stalting high in flush production, descending more or less steeply into the curve of settled production and dropping gradually to the vanishing point of economical operation. Together with this at somewhere in the early history of the field, there appears from a vanishing point a graph showing the production of water. During the period of settled production this graph rises higher and, toward the close, unless extensive work is done in the line of correction, rises far above the oil graph to where the cost of operation terminates profitable pumping. Fields that start out with a high relative content of water are generally very short lived. Fields that never develop a water problem are exceedingly rare.

Jan 1, 1930

By R. H. Dourson, B. H. Sage, W. N. Lacey

The compositions of coexisting phases in the methane-propane-n-pentane system were determined at 160° and -2 20°F. throughout the two-phase region, at pressures above 500 lb. per sq. in. The experimental results permitted the calculation of gas-liquid equilibrium constants as well as the establishment of the critical behavior of this ternary system. Although many binary paraffin hydrocarbon systems have been investigated, the experimental work relating to the phase behavior of ternary paraffin hydrocarbon mixtures at elevated pressures is relatively scarce, being limited to a study of the meth-ane-propane-PL-pentane system at 100°F.l,2 However, Guter and co-workers have studied the phase behavior of the methane-ethane-ethylene system at relatively low temperatures. Information concerning the phase behavior of ternary systems is of value in predicting the behavior of the components in multicomponent systems, since the influence of pressure, temperature, and concentration may be individually ascertained. In the light of the importance of such information, the study of this ternary system was extended to higher temperatures in order to increase the field of temperature in which the data could be applied. Since all states encountered in this investigation are above the critical temperature of methane, the details of its phase behavior are not of direct significance. The properties of propane in the heterogeneous region were taken from a correlation3 based upon recently published data. The corresponding information for n-pentane was taken from experimentally measured vapor pressures and volumetric data.4 The rnethane-propane system has been studied throughout the two-phase region at temperatures above 70°F.,5 while the phase behavior of the propane-n-pentane system has been established for temperatures above 160°F.6 The volumetric and phase behavior of the methane-72-pentane system has been studied in detai1.7,8 The experimental measurements serve to establish with adequate accuracy the phase behavior of the components and of the constituent binary systems for this ternary system. It is believed that, with the exception of the measurements for the methane-propane system, the uncertainties in the earlier data relating to the pure substances and the binary mixtures are probably less than those associated with the values reported here. Method The methods and apparatus employed in this investigation have been described.137 In principle, the method involved the withdrawal of samples of the coexisting gas and liquid phases from a vessel containing a heterogeneous mixture of methane, propane and n-pentane. Provision was made so that

Jan 1, 1943

By W. N. Lacey, R. H. Dourson, B. H. Sage

The compositions of coexisting phases in the methane-propane-n-pentane system were determined at 160° and -2 20°F. throughout the two-phase region, at pressures above 500 lb. per sq. in. The experimental results permitted the calculation of gas-liquid equilibrium constants as well as the establishment of the critical behavior of this ternary system. Although many binary paraffin hydrocarbon systems have been investigated, the experimental work relating to the phase behavior of ternary paraffin hydrocarbon mixtures at elevated pressures is relatively scarce, being limited to a study of the meth-ane-propane-PL-pentane system at 100°F.l,2 However, Guter and co-workers have studied the phase behavior of the methane-ethane-ethylene system at relatively low temperatures. Information concerning the phase behavior of ternary systems is of value in predicting the behavior of the components in multicomponent systems, since the influence of pressure, temperature, and concentration may be individually ascertained. In the light of the importance of such information, the study of this ternary system was extended to higher temperatures in order to increase the field of temperature in which the data could be applied. Since all states encountered in this investigation are above the critical temperature of methane, the details of its phase behavior are not of direct significance. The properties of propane in the heterogeneous region were taken from a correlation3 based upon recently published data. The corresponding information for n-pentane was taken from experimentally measured vapor pressures and volumetric data.4 The rnethane-propane system has been studied throughout the two-phase region at temperatures above 70°F.,5 while the phase behavior of the propane-n-pentane system has been established for temperatures above 160°F.6 The volumetric and phase behavior of the methane-72-pentane system has been studied in detai1.7,8 The experimental measurements serve to establish with adequate accuracy the phase behavior of the components and of the constituent binary systems for this ternary system. It is believed that, with the exception of the measurements for the methane-propane system, the uncertainties in the earlier data relating to the pure substances and the binary mixtures are probably less than those associated with the values reported here. Method The methods and apparatus employed in this investigation have been described.137 In principle, the method involved the withdrawal of samples of the coexisting gas and liquid phases from a vessel containing a heterogeneous mixture of methane, propane and n-pentane. Provision was made so that

Jan 1, 1943

By Alfonso W. Ovalle, Héctor R. Albornoz

INTRODUCTION The El Teniente Mine of Codelco-Chi le has extracted 588 mil lion tons of ore in its 77 year history for a total copper output of 8.800.000 tons. The mine production has been obtained mainly by traditional block-caving where grizzlemen using a hand held lever send ore through long-raises to load trains. At present the mine is about to introduce mechanized block-caving using LHD equipment to extract the primary rock. This paper describes this method which will be tested starting next month by caving an 11.000 square meter block. THE PRIMARY ROCK PROBLEM The secondary enrichment sulfides of the El Teniente ore body have characteristics which makes a standard unmechanized block-caving practice very successful. In the 60's parts of blocks encountered primary ow in the Teniente 1 and Sub-13 levels which proved to be extremely hard to extract. These foretold the obstacles that arised in the central part of the Teniente 4 level. Preparation of a completely primary 8.100 square meter block started in 1970. Its undercutting was completed by the end of 1972 and by 1973 the problem of mining the primary rock was clearly visualized. The numbers below describe the difficulties in mining this block: -Long-hole drilling rate is 90 m (270 ft) per shift in secondary rock and 37 m (110 ft) in primary. - Undercutting which is completed in 9 shifts in secondary took 180 shifts in the primary block. - Average grizzlymen productivity in secondary is 250 tons per shift while in primary it is only 25-30 tons, both at 343 mm (13 1/2 in. ) grizzly opening. - Powder consumption for secondary blasting increased from 8 grams per ton in secondary to 84 in primary. - The protection pillar between the under- cutting and the production levels was 60% broken in primary while 20% is usual for secondary. - Extraction advanced 5 cm per day in primary while a 50 cm per day rate is the aver- age in secondary. This is the main reason that after 8 years this primary block has a 20% extraction. Secondary blocks take 1.5 to 3 years to complete their extraction. - 80% of the boulders in primary rock are larger than 343 m (13 1/2 in.) with 10-20 % of them larger than 3 meters. -Direct cost of production (preparation, undercutting, extraction and haulage), using the traditional block-caving design for secondary rock, increased 3.5 to 4 times when used in primary rock. The following indicators of Table 1 show the rock characteristics differences.

Jan 1, 1981

By L. K. Oliver, Marshall

The use of model studies for the development of invasion patterns for cycling is .illustrated by model studies obtained with a recently developed apparatus in the solution of actual cycling problems. Introduction Depletion of a gas reservoir by cycling under pressure maintenance may be divided into three general phases. In the first phase, injection of dry gas is used to move all possible wet gas to producing wells prior to breakthrough of appreciable quantities of dry gas into producing wells. In the second phase, injection moves additional wet gas to producing wells while moderate quantities of dry gas are being produced. The third phase consists of production without injection to deplete the commercial gas reserve which remains after the cycling operation. Thus, in the first phase, a portion of the reservoir is invaded by dry gas, and the dry gas usually displaces something less than 100 pct of the wet gas from the invaded portions of the reservoir. The second phase enlarges the invaded portion of the reservoir and, at the same time, increases recovery from that zone invaded by dry gas in the first phase of the cycling operation. The result is an early yield of a substantial quantity of the liquefiable hydrocarbons in the reservoir with a minimum of the retrograde losses which occur in some reservoirs. The overall recovery from such an operation is usually high. The summation of the paths taken by dry gas in a cycling operation can be termed an invasion pattern. The use of electrical models to predict invasion patterns has been the subject of several contributions to the literature.1-3 The results of such model studies as applied to actual cases has been discussed by Kelton4 and Miller and Lents.= Recently, an improved apparatus for conducting potentiometric model studies has been developed, as described by Lee.V he purpose of this paper is to present model studies or invasion patterns obtained with this instrument in the solution of actual cycling problems. The percentage of displacement of wet gas within the invaded portion of the reservoir in cycling, increase in recoveries of wet gas by continuing cycling after dry gas breakthrough, recoveries of wet and dry gas by production after cycling, or economic factors in cycling are beyond the scope of this paper. Discussions which follow will be limited entirely to the development of suitable invasion patterns for cycling under pressure maintenance and the use of model studies therein. Discussion OF Results In using model studies to predict invasion patterns in cycling, some factors which influence the results are the following:

Jan 1, 1948

By Marshall, L. K. Oliver

The use of model studies for the development of invasion patterns for cycling is .illustrated by model studies obtained with a recently developed apparatus in the solution of actual cycling problems. Introduction Depletion of a gas reservoir by cycling under pressure maintenance may be divided into three general phases. In the first phase, injection of dry gas is used to move all possible wet gas to producing wells prior to breakthrough of appreciable quantities of dry gas into producing wells. In the second phase, injection moves additional wet gas to producing wells while moderate quantities of dry gas are being produced. The third phase consists of production without injection to deplete the commercial gas reserve which remains after the cycling operation. Thus, in the first phase, a portion of the reservoir is invaded by dry gas, and the dry gas usually displaces something less than 100 pct of the wet gas from the invaded portions of the reservoir. The second phase enlarges the invaded portion of the reservoir and, at the same time, increases recovery from that zone invaded by dry gas in the first phase of the cycling operation. The result is an early yield of a substantial quantity of the liquefiable hydrocarbons in the reservoir with a minimum of the retrograde losses which occur in some reservoirs. The overall recovery from such an operation is usually high. The summation of the paths taken by dry gas in a cycling operation can be termed an invasion pattern. The use of electrical models to predict invasion patterns has been the subject of several contributions to the literature.1-3 The results of such model studies as applied to actual cases has been discussed by Kelton4 and Miller and Lents.= Recently, an improved apparatus for conducting potentiometric model studies has been developed, as described by Lee.V he purpose of this paper is to present model studies or invasion patterns obtained with this instrument in the solution of actual cycling problems. The percentage of displacement of wet gas within the invaded portion of the reservoir in cycling, increase in recoveries of wet gas by continuing cycling after dry gas breakthrough, recoveries of wet and dry gas by production after cycling, or economic factors in cycling are beyond the scope of this paper. Discussions which follow will be limited entirely to the development of suitable invasion patterns for cycling under pressure maintenance and the use of model studies therein. Discussion OF Results In using model studies to predict invasion patterns in cycling, some factors which influence the results are the following:

Jan 1, 1948

By D. J. DeLazaro, D. W. Levinson

Observations were made of the isothermal transformation and quench and reheat transformation characteristics of binary titanium alloys containing nominally 6 wt pct and 10 wt pct Mn at temperatures of 700°, 600°, 500°, and 400°C. A large change in electrical resistivity attends the beta to alpha transformation in these alloys. The correlation between the resistivity and microstructure provides a very sensitive means of following the transformation. IN a recent paper, Wyatt' determined the electrical resistivity of several grades of unalloyed titanium metal as a function of temperature. In addition to the expected discontinuity accompanying the a-B transformation, it was shown that s-Ti has a much larger temperature coefficient of resistance than 8. The result would be a very large change in resistivity attending ß?a: transformation if it were possible to retain the ß structure at room temperature in pure titanium. From these data, it was reasoned that this very large resistance change should accompany the decomposition of the ß phase in alloys in which the ß phase can be retained by quenching to room temperature from the ß field. This effect is illustrated schematically in Fig. 1. Binary Ti-Mn alloys containing more than 5 wt pct Mn can be quenched to retain ß from the ß field. While the ß phase would be expected to transform in these alloys to a + TiMn via a eutectoid reaction,' it has been observed that the eutectoid decomposition does not occur readily in hypoeutectoid alloys, but rather the decomposition of the ß occurs by rejection of proeutectoid a only." Thus, the resistivity should show a marked decrease, as the a: phase is rejected from ß and a study of the resistivity of solution treated and isothermally transformed or quenched and reheated alloys should provide an excellent means of establishing the transformation kinetics of these alloys at various temperatures. The usual metallographic method of determining the transformation temperature-time characteristics of alloys of this type is very satisfactory for deter- mining the time required to initiate the rejection of the a phase at temperatures relatively close to the ß/a: + ß boundary when the rejected a is coarse, and a typical Widmanstaetten structure is produced. The metallographic method is less satisfactory for this purpose at lower temperatures where a fine nodular decomposition product is observed and is very unsatisfactory for the determination of the time required to complete the transformation at any temperature. Accordingly, specimens were prepared for resistivity measurements in order to determine the transformation characteristics of the alloys.

Jan 1, 1955

By J. R. Low, M. Gensamer

During the course of an investigation into the drawability of automobile-body sheet steel, it became apparent that certain advantages would be possessed by a deep-drawing steel with a very low yield strength, but almost normal tensile strength, provided a reduction in yield strength could be accomplished without sacrifice of ductility and fine grain size. It would also be desirable to have this steel free from strainaging; that is, free from the tendency for the yield point to return after it had been eliminated by straining. It was known that wet hydrogen treatment acted to eliminate aging, but as carried out by other investigators, at relatively high temperatures, this treatment resulted in grain coarsening. It has been established by some of the experiments reported in this paper that all of these objectives can be accomplished by treatment in wet hydrogen at a low temperature, in the neighborhood of 720°C. The time of treatment is relatively short (about 3 hr. to completion with 20-gauge sheet) if the water content of the hydrogen atmosphere is made fairly high, say almost 30 per cent by volume. At this temperature, the grain size remains fine in the time required. After this treatment sheet reduced the usual amount by cold-rolling has a grain size of about A.S.T.M. No. 7. The yield point is completely eliminated, and the yield strength is reduced to a very low value, in the neighborhood of 15,000 lb. per sq. in. The stress-strain curve departs gradually from the straight-line elastic part after the fashion of nonferrous deep-drawing alloys. This elimination of the yield point is accompanied by a very low indentation hardness; for example, 32 Rockwell B or even lower. There is no aging as measured by increase in the yield strength upon aging at room temperature or for 3 hr. at 200°C., after stretching about 10 per cent in tension. Tensile strength is only slightly less than the box-annealed sheet, seldom dropping much below 40,000 lb. per sq. in. Elongation is practically unchanged, or increased slightly. The term yield point, as here used, refers to the phenomenon of heterogeneous deformation occurring at a substantially constant load, observed principally in annealed low-carbon steels. If such a steel is loaded in tension, the load increases steadily with elastic strain, suddenly falls, fluctuates slightly about some constant value for a time and then begins to rise again as deformation proceeds. The maximum initial load before the sudden drop is generally called the "upper yield point"; the value of the load where deformation proceeds at a

Jan 1, 1943

By J. R. Low, M. Gensamer

During the course of an investigation into the drawability of automobile-body sheet steel, it became apparent that certain advantages would be possessed by a deep-drawing steel with a very low yield strength, but almost normal tensile strength, provided a reduction in yield strength could be accomplished without sacrifice of ductility and fine grain size. It would also be desirable to have this steel free from strain-aging; that is, free from the tendency for the yield point to return after it had been eliminated by straining. It was known that, wet hydrogen treatment acted to eliminate aging, but as carried out by other investigators, at relatively high temperatures, this treatment resulted in grain coarsening. It has been established by some of the experiments reported in this paper that all of these objectives can be accomplished by treatment in wet hydrogen at a low temperature, in the neighborhood of 72o°C. The time of treatment is relatively short (about 3 hr, to completion with 20-gauge sheet) if the water content of the hydrogen atmosphere is made fairly high, say aimost 30 per cent by volume. At this temperature. the grain size remains fine in the time required. After this treatment sheet reduced the usual amount by cold-rolling has a grain size of about A.S.T.M. No. 7. The yield point is completely eliminated, and the yield strength is reduced to a very low value, in the neighborhood of 15,000 lb. per sq. in. The stress-strain curve departs gradually from the straight-line elastic part after the fashion of nonferrous deep-drawing alloys. This elimination of the yield point is accompanied by a verv low indentation hardness; for example, 32 Rockwell B or even lower. There is no aging as measured by increase in the yield strength upon aging at room temperature or for 3 hr. at 200°C., after stretching about 10 per cent in tension. Tensile strength is only slightly less than the box-annealed sheet, seldom dropping much below 40,-ooo lb. per sq. in. Elongation is practically unchanged, or increased slightly. The term yield point, as here used, refers to the phenomenon of heterogeneous deformation occurring at a substantiallv constant load, observed principally in annealed low-carbon steels. If such a steel is loaded in tension, the load increases steadily with elastic strain, suddenly falls, fluctuates slightly about some constant value for a time and then begins to rise again as deformation proceeds. The maximum initial load before the sudden drop is generally called the "upper yield point"; the value of the load where deformation proceeds at a

Jan 1, 1944

By J. R. Low, M. Gensamer

During the course of an investigation into the drawability of automobile-body sheet steel, it became apparent that certain advantages would be possessed by a deep-drawing steel with a very low yield strength, but almost normal tensile strength, provided a reduction in yield strength could be accomplished without sacrifice of ductility and fine grain size. It would also be desirable to have this steel free from strain-aging; that is, free from the tendency for the yield point to return after it had been eliminated by straining. It was known that, wet hydrogen treatment acted to eliminate aging, but as carried out by other investigators, at relatively high temperatures, this treatment resulted in grain coarsening. It has been established by some of the experiments reported in this paper that all of these objectives can be accomplished by treatment in wet hydrogen at a low temperature, in the neighborhood of 72o°C. The time of treatment is relatively short (about 3 hr, to completion with 20-gauge sheet) if the water content of the hydrogen atmosphere is made fairly high, say aimost 30 per cent by volume. At this temperature. the grain size remains fine in the time required. After this treatment sheet reduced the usual amount by cold-rolling has a grain size of about A.S.T.M. No. 7. The yield point is completely eliminated, and the yield strength is reduced to a very low value, in the neighborhood of 15,000 lb. per sq. in. The stress-strain curve departs gradually from the straight-line elastic part after the fashion of nonferrous deep-drawing alloys. This elimination of the yield point is accompanied by a verv low indentation hardness; for example, 32 Rockwell B or even lower. There is no aging as measured by increase in the yield strength upon aging at room temperature or for 3 hr. at 200°C., after stretching about 10 per cent in tension. Tensile strength is only slightly less than the box-annealed sheet, seldom dropping much below 40,-ooo lb. per sq. in. Elongation is practically unchanged, or increased slightly. The term yield point, as here used, refers to the phenomenon of heterogeneous deformation occurring at a substantiallv constant load, observed principally in annealed low-carbon steels. If such a steel is loaded in tension, the load increases steadily with elastic strain, suddenly falls, fluctuates slightly about some constant value for a time and then begins to rise again as deformation proceeds. The maximum initial load before the sudden drop is generally called the "upper yield point"; the value of the load where deformation proceeds at a

Jan 1, 1944

By R. A. Pasternak, B. Evans

In an ultrahigh-vacuum study of the sorption of nitrogen by niobium* resistivity data for this metal have been obtained as function of temperature and of low nitrogen concentrations. The ultrahigh-vacuum system in which base pressures of about 5 x l0-10

Jan 1, 1965

"Only the coal of the Sunnyside district in Carbon County is coked. Two companies, the Utah Fuel Company and the Columbia Steel Corporation, operating adjoining mines at Sunnyside and Columbia, produce coke.The Utah Fuel Company has 819 beehive coke ovens at Sunnyside. Only 350 ovens are being operated at the present time, largely because the smelters which had been using Sunnyside coke changed their equipment from blast furnaces to reverberatory furnaces.The Columbia Steel Corporation operates a plant of 33 Koppers type by-product coke ovens at Ironton, near Provo. About 800 tons of coal are used per day to produce coke for the company's iron blast furnace plant pie ovens produce about 400 tons of coke, 12,000,000 cubic feet of gas, 9,000 gallons of coal tar, 3,000 gallons of benzol and several tons of ammonia sulphate per day.The total coke production for the State from the earliest output of record in 1880 until June 30, 1924, is 5,947,714 tons."

Jan 1, 1925

By Morris Cohen

This paper deals with the calculation of the composition of the infinitesimal trace of alloy that transfers from the liquid to the solid state at each temperature during the equilibrium solidification of a binary solid solution, and which thereby enables the compositions of the coexisting liquid and solid phases to follow along the liquidus and solidus lines respectively during the cooling. A general expression for the composition (S) of the liquid-to-solid transfer at each temperature has been derived S - ZLXL(XL - P) + Zsxs(P - XS) ZL(xL - P) + Zs(P - XS) where ZL and Zs are the slopes of the liquidus and solidus lines at the given temperature, XL and xs are the composi-tions of the stable liquid and solid phases at the same temperature, and P is the composition of the alloy under considera-tion. The S equation is valid for the process of equilibrium heating as well as cooling, and may be applied to vapor-to-liquid, vapor-to-solid, liquid-to-liquid, and solid-to-solid transfers if the corresponding equilibrium diagrams are known.

Jan 1, 1940

By James J. Bailey

Percussive drills have been in commercial use for many decades. Until relatively recently there was little serious effort to analyze the stresses in such devices in any detail. Within the last few years such analyses have been developed and have been reported by a number of authors.1-4 We present here an investigation of the impact systems of a family of conventional down-hole drills with optimization the objective. We have assumed that maximum drilling speed was the quality most desired and that this was to be achieved within conventional practice. In fact the methods that are demonstrated in principle below can readily be adapted to other percussive devices, whether conventional or not, and to other constraints. SOME PERFORMANCE PARAMETERS FOR PERCUSSIVE DRILLS Consider a percussive drill with an air motor operating with the following parameters: p-supply air pressure a-effective piston area W-piston mass S-piston stroke If we consider a simple (constant pressure) cycle, the following relationships can be derived. The blow frequency [N~ pa lie WS 377]

Jan 1, 1968

By J. M. Lommel, B. Chalmers

The transfer of material from the solid to the liquid states can be accomplished in several ways. It occurs by the application of heat in the more familiar metallurgical operations of melting but it can also be accomplished by solution in a liquid, as can occur in systems using liquid metals for heat-transfer media. The kinetics of this reaction were studied to learn more of the separate steps in the process. In the case of a pure material at its melting temperature, Te,A,, thermal energy must be supplied to the solid in an amount equal to the latent heat of fusion in order for the solid-to-liquid transfer to occur. The rate at which heat is supplied, and hence the rate of melting, is a function of the temperature gradients in the system. This phase transfer can also occur in the absence of temperature gradients in the system illustrated in Fig. 1, which is a partial phase diagram between the components A and B. A solid of composition CI will

Jan 1, 1960

Alfred E. Hunt, Pittsburgh, Pa. (communication to the Secretary): My experience has been similar to that described by Mr. Sperry, regarding a 50 per cent. alloy of nickel and aluminum. Moreover, the same phenomena occur with a 50 per cent. alloy of iron and aluminum, manganese and aluminum, chromium and aluminum, or tin and aluminum. It seems that there is a narrow limit of composition of these metals, within which, when they are alloyed, they crumble down into a powder after standing for any considerable time. The resulting powder does not seem to be a separation or disintegration into the elements composing the alloy, but simply a powdering down of the alloy itself. The physical properties and utility of any of these alloys in pondered form have not been carefully investigated as yet, and offer a field worthy of further investigation. Samuel Peters, Pittsburgh, Pa. (communication to the Secretary) : In the early seventies, during the early days of the open-hearth process in this country, the writer was engaged as

Jan 1, 1900

By Meguru Nagamori

DURING the smelting of the sulfide ores of copper, nickel, and certain other metals, a matte phase is formed. For a better understanding of the physico-chemical properties of mattes, binary systems such as Cu-S, Ni-S, Fe-S, and so forth, should be studied, especially in the vicinity of liquid compounds such as Cu2S, Ni3S2, FeS, and so forth. These compounds are relatively stable in the solid state although they can exhibit appreciable deviations from stoichiometry. With small deviations from stoichiometry there are large changes in the activity of both sulfur and metal this is a characteristic of both solid and liquid sul-fides near the stoichiometric compositions. In the vicinityof molten Cu2S,1 for instance, the activity of sulfur increases about 100 times for a 0.012 increase in the mole fraction of sulfur and, correspondingly, the activity of copper decreases greatly. In this sens the minor deviations from stoichiometry should be carefully taken into account in studies of such metal-sulfur melts. Metal-sulfur melts may be considered to have properties intermediate between metallic solutions and molten salts, i.e., neither entirely metallic nor entirely ionic. The radius of the ion sZ- is 1.84 as compared with 1.04? for a single bond covalent s.2 It is therefore inferred that when the sulfur is more ionic its partial molar volume is larger, although metal-metal, metal-sulfur, and sulfur-sulfur interactions may bring about further complexities. Thus, it is to be expected that the molar volumes, which are derived from density-composition relations, will help in resolving the structure of the melts. In this study the maximum bubble pressure method with bubbling gases of H2, H2S, and Ar, .was employed to measure the density. EXPERIMENTAL Materials. Silver of 99.95 pct purity was melted in an alumina crucible and hydrogen gas was then bubbled through the liquid for the deoxidation. In preparation of Cu2S, electrolytic copper powder (>99.9 pct Cu) was mixed with precipitated sulfur and heated to 1200°C in an alumina crucible under a hydrogen atmosphere. Mixtures having the approximate compositions FeS and Ni3S2 were prepared by heating reagent grade electrolytic iron or reduced nickel powder with precipitated sulfur under a hydrogen atmosphere. The H2S gas was of 98.5 pct purity, the impurities being mostly CO2 and CS2 which hardly contaminate the melts. Apparatus. The crucible system is shown schematically in Fig. 1. To minimize the variation of melt composition during a density measurement, the apparatus was designed in such a way that either Ar, H2, H2S, or mixtures of these gases could be used as the bubbling gas. When the melt had a high partial pressure of sulfur, H2S gas was used. When the partial pressure of sulfur was so low that oxygen might dissolve in the melt, the use of H2 was preferred. In intermediate cases, argon or mixtures of H2-H2S were used. Density of Dibutylphtalate. Dibutylphtalate was used as the manometer fluid. Relative to distilled water, the density of the dibutylphtalate, pdib g per cc, was measured and found to be: pdib (25°C) = 1.046 i 0.002. With the use of the temperature coefficient reported by Kemppinen and Gokcen,3 the following value was

Jan 1, 1970

By George P. Chapman

Mica is a platy mineral occurring in a variety of complex hydrous aluminosilicate forms with differing chemical composition and physical properties. Principal minerals in the mica group include: Muscovite-potassium mica (colorless or pale green/ ruby) Phlogopite-magnesium mica (dark brown or amber) Biotite-magnesium-iron mica (black or dark green) Lepidolite-lithium mica (lilac) Selected properties are given in Table 1. Muscovite is most important commercially with phlogopite of lesser use. The laminated structure of mica enables it to be split into very thin films which are transparent and tough as well as having outstanding dielectric and insulating properties. Commercially, mica is used in a number of forms (Chowdbury, 1941; Rajgarhia, 1951; Skow, 1962). Sheet mica consists of flat sheets mined from naturally occurring books of mica, free from defects and capable of being punched or stamped into required shapes. Sheet mica is separately classified into blocks, films, or splittings according to thickness. Built-up mica, or micanite, is made by arranging overlapping splittings in layers , cemented with a binder and pressed together at high temperature. Reconstituted mica, or mica paper, is made by depositing fine flakes of high-quality scrap mica in a continuous film impregnated with binder. Scrap and flake mica are normally unsuitable in quality or size for making sheet mica. Originally the term scrap mica referred to the waste byproduct of mining and fabricating sheet mica, and distinct uses were developed for this material. Subsequently it became economically feasible to mine lower quality mica for these uses, and the term flake mica was introduced. Although the two terms are still used somewhat synonymously, it is considered better, at least in the United States, to use the term flake mica in referring to mica mined for uses other than as sheet mica; and to restrict the term scrap mica to mica mined for or with sheet mica, but which will not meet the specifications. Synthetic mica, such as fluorophlogopite, is produced by slow crystallization of a melted blend of pure raw materials. Mineralogy In the true sense the term mica does not relate to, a particular mineral, but to a group or family of minerals of similar chemical composition and to some extent similar physical properties. These minerals are predominantly potassium aluminum silicates with varying amounts of magnesium, iron, and lithium. The precise formulas and isomorphic relationships of the various group members have been studied, but general agreement has not been reached (Grimshaw, 1971; Hurlbut, 1952; Skow, 1962). The general formula describing the chemical composition of micas is [X2Y4-6Z8020(OH, F)4, where X is mainly K, Na, or Ca; Y is mainly Al, Mg, or Fe; Z is mainly Si or Al (Deer, et al., 1962).] These minerals have an internal structure of the layered lattice type where the silicon atoms are in the center of a tetrahedral grouping of oxygen atoms. The groups are linked together in a single plane by three oxygen atoms that lie within the common plane. Each of these oxygen atoms is shared by two tetrahedra. These linked tetrahedral groups, when continually extended, produce a hexagonal network within the plane. This internal structure of the mica has been used to explain the ex-

Jan 1, 1983