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By M. D. Hassialis, A. F. Taggart

ark' observed some years ago that collector-coating reactions with xanthates and with fatty acids clearly follow paths parallel to those prescribed by the familiar mass-action law for reactions in dilute solutions. He proposed, therefore, the logical hypothesis that they are governed by the solubility-product principle. However, he went astray in the application of his proposal to collector coating by overlooking the fact that coating involves a heterogeneous reaction. A mistaken concept of the meaning of the word adsorption also entered. Wark thought that the concentration of metallic ion that must be used in setting up the solubility-product equation for the coating reaction was that which could be obtained by solution of the mineral. Since this is very low for sulphide ores, and since the amount of the collector ion necessary for coating produces an extremely low concentration, the resulting ion-concentration product, under conditions when coating occurs, is much lower than that which would indicate a saturated solution of the collector-coating compound. Hence he was forced to the position that the solubility product governing the coating is much smaller than the standard solubility product. To justify this position it was necessary to postulate a coating mechanism that did not obey the ordinary laws of chemical reaction. This Wark did by adopting the concept that adsorption is a property of matter, rather than merely a more or less ephemeral local concentration thereof. Thus he says (p. 142 of ref. I): "Adsorption is not a purely physical property of the solid surface, for the specific nature of the adsorbed molecule or ion is important." The result was that he destroyed the great potential utility of his postulate by tying it to this erroneous concept in the words (pp. 142, 143): "It will be obvious that the adsorption solubility product is less than the normal solubility product." The writers have found quantitatively in the case of galena and potassium ethyl xanthate, and semiquantitatively in the case of covellite and the same collector, that the coating reaction does follow the mass-action law to the extent that coating occurs when the ordinary solubility product of the coating compound is exceeded, and that coating does not take place under the reverse conditions. In the course of the investigation leading to the establishment of this fact it was necessary to work with xanthate concentrations so low (down to 0.0004 mg. per liter), that very long conditioning times, and bubble-contact times of as much as 16 hr. were necessary sometimes to follow the reactions. The results have led to some illuminating conclusions as to necessary collector concentrations in normal flotation operations, and the action of the frothing agent in connection therewith' The experimental work comprised accurate determination of the standard solubility product of lead ethyl xanthate, development of a much less laborious

Jan 1, 1947

By C. G. Southmayd

Anyone who has been confronted with the problem of predicting the performance of a sand-pump installation is vitally aware of the dearth of precise information that has been published on this important subject. Such data as have been collected are not readily available in a concise and readily usable form, so that many operators would find it a considerable chore to find the pertinent information required to undertake a detailed study. The purpose of this paper is to assemble such established data, correlate them with field experience and outline the factors that must be appraised in the determination of a satisfactory pump installation. The transportation of solids in solution is of vital interest to every mill superintendent and operator, and many of the factors that are involved in this hydraulic problem vary widely from installation to installation, and in some cases even from time to time on any one installation. These include: type of solids (including shape of particles), size of solids (grind), percentages of fines (slimes), dilution of pulp, contour of pipe line, type of pipe, age of pipe line, effect that diameter of pipe has on characteristic flow conditions, and other factors. Some of these have been fairly well determined by experimental work but many still must be established through interpolating or extrapolating between values that have been derived from known field conditions. Most problems primarily concern the transportation of a definite weight of dry solids from one specific location to another. The type of material, shape of particles, grind and percentages of fines are established and very often the dilution at which the solids must be handled as well. The problem then evolves into a determination of the size, type and contour of the pipe line and the net effective head against which the pump must operate. Before discussing the determination of the head, it might be well to review the interrelationship between the pump discharge (capacity), the head developed by the pump and the pump speed, which will apply to any centrifugal pump installation. Effect of Pump Speed Basically, the head developed by a centrifugal pump varies as the square of the pump speed and the discharge as the first power of the speed. However, even at constant speed a centrifugal pump will operate over a wide range of capacities, depending upon the head that must be developed to deliver the liquid or pulp to the end of the pipe line. This is shown graphically in Fig. I. If the pump in question is being driven at a constant speed of goo r.p.m. it will deliver 500 U. S. gal. per min. against a head of 56 ft., 800 U. S. gal. per min. against a head of 50 ft., and so on. In other words, at this speed the capacity of the pump will be determined and limited by

Jan 1, 1947

By C. G. Southmayd

Anyone who has been confronted with the problem of predicting the performance of a sand-pump installation is vitally aware of the dearth of precise information that has been published on this important subject. Such data as have been collected are not readily available in a concise and readily usable form, so that many operators would find it a considerable chore to find the pertinent information required to undertake a detailed study. The purpose of this paper is to assemble such established data, correlate them with field experience and outline the factors that must be appraised in the determination of a satisfactory pump installation. The transportation of solids in solution is of vital interest to every mill superintendent and operator, and many of the factors that are involved in this hydraulic problem vary widely from installation to installation, and in some cases even from time to time on any one installation. These include: type of solids (including shape of particles), size of solids (grind), percentages of fines (slimes), dilution of pulp, contour of pipe line, type of pipe, age of pipe line, effect that diameter of pipe has on characteristic flow conditions, and other factors. Some of these have been fairly well determined by experimental work but many still must be established through interpolating or extrapolating between values that have been derived from known field conditions. Most problems primarily concern the transportation of a definite weight of dry solids from one specific location to another. The type of material, shape of particles, grind and percentages of fines are established and very often the dilution at which the solids must be handled as well. The problem then evolves into a determination of the size, type and contour of the pipe line and the net effective head against which the pump must operate. Before discussing the determination of the head, it might be well to review the interrelationship between the pump discharge (capacity), the head developed by the pump and the pump speed, which will apply to any centrifugal pump installation. Effect of Pump Speed Basically, the head developed by a centrifugal pump varies as the square of the pump speed and the discharge as the first power of the speed. However, even at constant speed a centrifugal pump will operate over a wide range of capacities, depending upon the head that must be developed to deliver the liquid or pulp to the end of the pipe line. This is shown graphically in Fig. I. If the pump in question is being driven at a constant speed of goo r.p.m. it will deliver 500 U. S. gal. per min. against a head of 56 ft., 800 U. S. gal. per min. against a head of 50 ft., and so on. In other words, at this speed the capacity of the pump will be determined and limited by

Jan 1, 1947

By W. C. Ellis

Growth directions of tin, zinc, and cadmiun whisker crystals grown spontaneously fi-om the solid are summarized. In tin the edge and diagonal directions of the unit cell are jound with the exception oj- the [110] diagonal. In cadmiurn and zinc the usual dip-ections are a or a + c. The c direction has not been ohserwed. The gvouth directions from the solid are for the most part the same as those found for vapor-grozun crystals and are the ohserz:ed glide directions in plastic j-lou. Whisker crystals of these elements grown from the solid are not twinned. Specular lateral reflections are associated with planes of snall crystallographic indices. WHISKER crystals of tin, zinc, or cadmium grow spontaneously at room temperature in periods from months to years from thin electroplates and other prepared films of the respective metals.''2 It has been established that these crystals are single, but the question of twinning, such as occurs in whisker crystals of silicon,3'4 has not been resolved. Studies of morphology have been restricted to determinations of growth directions.5-' Whisker crystals are both straight and kinked. A few studies have been made on kinked whiskers including measurements of kink anglesa and determinations of growth directions,' but unfortunately not both on the same crystals. The kink angles, for the most part, for each species are grouped closely about a few unique values, but these values are not always those between observed growth directions in a single crystal. To supplement existing data, the growth directions, identification of lateral features, and presence or absence of twinning were determined with a Weissenberg goniometer by a method described elsewhereg on eight whisker crystals of tin, five of zinc, and five of cadmium. One kinked cadmium whisker was examined in detail. The specimens were needlelike, a few microns in cross section, and of the order of a millimeter in length. They were removed from electroplated substrates on laboratory specimens and commercial equipment after several years of growth as described in Table I. Since the specimens were less than 10 p in cross section they were ideally strong with no attendant risk of plastic deformation or damage in handling. Only deformation twinning has been reported for these elements. Therefore, twinning probably should not be expected in whisker crystals of these metals, particularly a twin plane containing the growth direction. A twin plane oriented in this direction was the one sought in this study. No examination was made for twinning at the boundary between kink segments except for one cadmium crystal. Well-defined reflections occur as a whisker crystal of tin, zinc, or cadmium is rotated about its growth direction when illuminated by a beam of light Although these reflections had been noted in earlier investigations, no study of them was made, probably because the earlier studies had disclosed also that

Jan 1, 1967

By G. A. Colligan, G. L. F. Powell

A new experimental technique has been developed to study nucleation behavior in eutectic alloys. It is somewhat similar to that applied by Sundquist and Mondolfo1 but with the advantages that: 1) bulk samples are undercooled instead of small droplets thus allowing the thermal behavior to be monitored by a thermocouple immersed in the sample, and 2) nucleation behavior is investigated in the same sample on either side of the eutectic composition by adding additional component to the sample under controlled conditions which preclude the addition of nu-cleation contaminants. Sundquist and Mondolfo carried out ]nucleation ex-periments on a large number of eutectic alloy sys-tems and concluded that nonreciprocal nucleation operated. If one phase a was a good nucleant for the other phase 0, then B was a poor nucleant for a. This was determined experinlentally by comparing the nucleation temperatures of 100 to 300 u diameter droplets of hypereutectic and hypoeutectic composition cooled from above the liquidus and from a temperature between the liquidus and the eutectic temperature. Primary phase a was concluded to be an efficient nucleant for the other phase B, if the following experimental result was obtained. Referring to Fig. 1, the temperature TI at which a drop of hypereutectic alloy of composition B froze when cooled from above the B liquidus was noted. This was the nucleation temperature for B in the absence of a. A drop of hypoeutectic alloy of composition A was then frozen from temperature T2 between the a liquidus and the eutectic temperature. The temperature T3 at which the eutectic nucleated in the presence of the primary or proeutec-tic a was noted. If this temperature T3 was higher than the temperature TI at which the B nucleated in a hypereutectic alloy, it was concluded that the primary a had nucleated the 6. This temperature T3, representing a certain undercooling below the equilibrium eutectic temperature Te , was designated ?TB by a> the undercooling below T, for nucleation of 13 by a. If there was no substantial difference in nucleation temperature between the hypereutectic drop cooled from above the /3 liquidus and the hypo-eutectic drop cooled from a temperature between the a liquidus and the eutectic temperature, it was considered that the a nucleated B at an undercooling equal to or greater than that at which P nucleated from a hypereutectic alloy. Sundquist and Mondolfo1 found that faceted primary crystals were good nucle-ants for metals that grow as orthogonal dendrites when present as the primary phase. Jackson2 has questioned Sundquist and Mondolfo's technique and proposed that in Sundquist and Mon-dolfo's samples, such as composition A, primary a retained B in reentrant grooves at their surfaces when heated to a temperature above the eutectic but below the a liquidus. This objection was suggested by experiments with organic eutectics where reten-

Jan 1, 1970

By D. A. Dukelow, G. Derge

THE Fe0-Mn0-Si0, system has many properties of fundamental interest besides its occurrence in steel-making. The system is the simplest ternary complication of the FeO-SiO, binary whose electrochemical properties have been explored. Therefore, knowledge of the conformance of Fe0-MnO-SiO, melts to Faraday&apos;s laws, as investigated by current efficiency measurements, would be of particular value in interpreting the observed variations of electrical conductivity, while at the same time furthering understanding of this type of molten oxides. Pertinent to the present study are conductivity data of FeO-SiO, and Fe0-Mn0-SiO2, and current efficiency data of FeO-SiO,. Concerning conductivity measurements, Inouye, Tomlinson, and chipman&apos; studied the specific conductivity, a, of molten wüstite as a function of temperature and oxide addition. Liquid FeO in equilibrium with an iron crucible was found to have a o whose magnitude and positive temperature coefficient were undeniably semiconductor in nature (o1400°C = 269 ohm-1cm-&apos;). Additions at 1400°C of 5 mole pct MnO decreased o to 227 while a similar addition of SiO2, dropped o to 125. Additional SiO2 produced an exponential decline of o. It was reasoned that because wüstite is known to be oxygen excess and since there is no pronounced change in oFeO upon melting, that UFeO(L)is p-type semiconduction. Björling2 gives o data for the ternary FeO-MnO-SiO, using fayalite, 2 FeO-SiO,, as the base substance. Upon addition of tephroite, 2 MnO-SiO, he noted a small decrease in o. Taking his data for 1400°C with one-half of the fayalite replaced by tephroite, o shows a decrease of some 40 pct relative to o for fayalite, i.e., 5 ohm-&apos; cm-&apos; to 3. In line with this observation, Mori and Matsushita3 reported that substituting MnO for FeO in the silicate de- creased o slightly except at high SiO, contents where the decrease was somewhat larger. Investigating the ionic nature of FeO-SiO2 melts, Simnad, Derge, and George4, found the anode current efficiency, C,, as calculated from iron anode weight loss, was temperature invariant and in general increased with SiO2 concentration. The authors suggested the possible presence of electronic conduction to explain why C+ < 100 pct. Fig. 4 includes their results as curve (b). EXPERIMENTAL METHOD Apparatus—Fig. 1 is a schematic section of the electrolysis cell used in all the current efficiency runs. The melt was contained in an iron crucible that rested on an alundum ring. A centered silica tube came within 1 in. of the surface of the melt and initially served as a thermocouple well and then as the guide for the anode.

Jan 1, 1961

By Walter Miller

During the second year of America&apos;s active ia in the war the inain objectives of the petroleum-refining industry were again to provide the four most important product needs for war: 100-octane aviation gasoline, toluene for T.N.T. production, high-quality lubricating oils for the needs of aviation and the armed forces, and petroleum chemicals for synthetic rubber manufacture. All other materials supplied by the petroleum industry took an inferior priority ranking, depending on the degree of essentiality. To accomplish the above objectives the industry initiated and carried on a building program during 1942 and 1943 which will put those two years down in petroleum-refining history as the greatest construction years of all time, a record which will hold for decades to come. Led by an estimated total of $ 900,000,000 going into 100-octane and contributory plant investment, it is easy to picture a total of two billion dollars and more going into additional refining-industry plant investment during 1942 and 1943, most of it privately paid for, but a substantial part covered by R.F.C. Government money financing. Some of the new plants will not be completed until 1944, but a large proportion of the program was finished and put into operation, adding substantially to the output of the four principal products during 1943- lne most important and spectacuiar activity of the refining industry is of course the 100-octane gasoline program necessitated by the fact that nearly 90 per cent of the requirements of the United Nations is being furnished by the United States. Recent P.A.W. figures mention $goo,-ooo,ooo as the cost of the construction looking to increasing the output of this all-important munition. Thirty-four major plants have been completed, 11 of them during the last quarter of the year. Thirty-eight more will be completed and put into operation during the first four or five months of 1944. Twenty-two additional plants authorized during 1943 are already well under way and scheduled for production late in 1944. Early in 1942 the aim was to treble the capacity for making 100-octane gasoline then existing; later, plans were to make it five times as great, to match the increased warplane building program; and toward the end of the year the sights had been set at a still higher but unannounced target, representing six to seven times the early 1942 figure. Comparative figures issued at the end of 1943 enable one to guess a program by the middle of 1944 of eight to nine times the former production, with an ultimate production in 1944 of eleven or more times the early 1942 output. It became obvious in 1943 that building of new units would be materially slowed because of delay in getting construction materials and that they would reach operation at considerably later dates than

Jan 1, 1944

By Walter Miller

During the second year of America&apos;s active ia in the war the inain objectives of the petroleum-refining industry were again to provide the four most important product needs for war: 100-octane aviation gasoline, toluene for T.N.T. production, high-quality lubricating oils for the needs of aviation and the armed forces, and petroleum chemicals for synthetic rubber manufacture. All other materials supplied by the petroleum industry took an inferior priority ranking, depending on the degree of essentiality. To accomplish the above objectives the industry initiated and carried on a building program during 1942 and 1943 which will put those two years down in petroleum-refining history as the greatest construction years of all time, a record which will hold for decades to come. Led by an estimated total of $ 900,000,000 going into 100-octane and contributory plant investment, it is easy to picture a total of two billion dollars and more going into additional refining-industry plant investment during 1942 and 1943, most of it privately paid for, but a substantial part covered by R.F.C. Government money financing. Some of the new plants will not be completed until 1944, but a large proportion of the program was finished and put into operation, adding substantially to the output of the four principal products during 1943- lne most important and spectacuiar activity of the refining industry is of course the 100-octane gasoline program necessitated by the fact that nearly 90 per cent of the requirements of the United Nations is being furnished by the United States. Recent P.A.W. figures mention $goo,-ooo,ooo as the cost of the construction looking to increasing the output of this all-important munition. Thirty-four major plants have been completed, 11 of them during the last quarter of the year. Thirty-eight more will be completed and put into operation during the first four or five months of 1944. Twenty-two additional plants authorized during 1943 are already well under way and scheduled for production late in 1944. Early in 1942 the aim was to treble the capacity for making 100-octane gasoline then existing; later, plans were to make it five times as great, to match the increased warplane building program; and toward the end of the year the sights had been set at a still higher but unannounced target, representing six to seven times the early 1942 figure. Comparative figures issued at the end of 1943 enable one to guess a program by the middle of 1944 of eight to nine times the former production, with an ultimate production in 1944 of eleven or more times the early 1942 output. It became obvious in 1943 that building of new units would be materially slowed because of delay in getting construction materials and that they would reach operation at considerably later dates than

Jan 1, 1944

By M. D. Hassialis, Arthur F. Taggart

WARK1 observed some years ago that collector-coating reactions with xanthates and with fatty acids clearly follow paths parallel to those prescribed by the familiar mass-action law for reactions in dilute solutions. He proposed, therefore, the logical hypothesis that they are governed by the solubility=product principle. However, he went astray in the application of his proposal to collector coating by overlooking the fact that coating involves a heterogeneous reaction. A mistaken concept of the meaning of the word adsorption also entered. Wark thought that the concentration of metallic ion that must be used in setting up the solubility-product equation for the coating reaction was that which could be obtained by solution of the mineral. Since this is very low for sulphide ores, and since the amount of the collector ion necessary for coating produces an extremely low concentration, the resulting ion-concentration product, under conditions when coating occurs, is much lower than that which would indicate a saturated solution of the collector-coating compound. Hence he was forced to the position that the solubility product governing the coating is much smaller than the standard solubility product. To justify this position it was necessary to postulate a coating mechanism that did not obey the ordinary laws of chemical reaction. This Wark did by adopting the concept that adsorption is a property of matter, rather than merely a more or less ephemeral local concentration thereof. Thus he says (p. 142 of ref. I): "Adsorption is not a purely physical property of the solid surface, for the specific nature of the adsorbed molecule or ion is important." The result was that he destroyed the great potential utility of his postulate by tying it to this erroneous concept in the words (pp. 142, 143): "It will be obvious that the adsorption solubility product is less than the normal solubility product." The writers have found quantitatively in the case of galena and potassium ethyl xanthate, and semiquantitatively in the case of covellite and the same collector, that the coating reaction does follow the mass-action law to the extent that coating occurs when the ordinary solubility product of the coating compound is exceeded, and that coating does not take place under the reverse conditions. In the course of the investigation leading to the establishment of this fact it was necessary to work with xanthate concentrations so low (down to 0.0004 mg. per liter), that very long conditioning times, and bubble-contact times of as much as 16 hr. were necessary sometimes to follow the reactions. The results have led to some illuminating conclusions as to necessary collector concentrations in normal flotation operations, and the action of the frothing agent in connection therewith. The experimental work comprised. accurate determination of the standard solubility product of lead ethyl xanthate, development of a much less laborious

Jan 1, 1946

By E. Hein, R. A. Dodd

The fatigue softening of prior strain-hardened poly crystalline copper has been determined by measuring changes inflow stress resulting from fatigue treatments. Tensile fatigue does not soften the metal, while the softening due to reversed stress fatigue depends on the extent to which fully reversed stressing is approached. True tensile fatigue is shown to be possible only in the case of long wire specimens. Annealing following fatiguing of strain-hardened metal shows that tensile fatigue is very effective in modifying normal recovery and recrys-tallization. OBSERVATIONS by Ludwik and Scheu,&apos; Kenyon,&apos; Polakowski and Palchoudhuri, Kemsley, and Broom and Ham,596 have shown beyond doubt that strain-hardened metals are softened by reversed-stress fatigue. To some extent the softening might be associated with a rearrangement of dislocations, but the results of Broom and Ham5 on the temperature dependency of the fatigue hardening of annealed copper, and those of McCammon and Rosenberg7 on the partial recovery at 100&apos;C of fatigue-hardened copper suggest that point defects may be involved. Since lattice vacancies are the only species of point defect present in appreciable quantities in thermody-namic equilibrium, most attention has been accorded them in the various theories advanced to explain hardening and softening effects resulting from fatigue. Precise mechanisms remain uncertain, and while some effects may be due to single vacancies, defects arising from vacancy clusters may also contribute to the changes in properties. All types of plastic deformation result in point-defect formation, one frequently invoked formation mechanism involving the nonconservative motion of jogs formed by the intersection of, for example, mixed dislocations. But since fatigue deformation is thought to be a particularly effective way of forming point defects, additional mechanisms peculiar to fatigue must be sought. One possibility is that jogged loops contract during the unloading cycle to give rows of vacancies. A local high-vacancy concentration could conceivably promote polygonization and recovery by climb, and, therefore, could explain the fatigue softening of strain-hardened metals under appropriate conditions of temperature. Conversely, the experiments by Broom and Ham6 on the fatigue hardening of copper single crystals involving subsequent tensile testing of previously fatigued specimens, resulted in the observation of distinctly lowered yield points. This could be due to vacancy atmospheres associated with dislocations, possibly augmented by jogs on dislocations. In addition to the yield-point phenomenon, a post-yield hardening was observed, with a temperature-dependence resembling the friction-hardening of irradiated metals,9 this again suggesting a point-defect mechanism. An important development in this field has been the observation,10 by transmission electron microscopy, of high concentrations of prismatic loops in fatigued aluminum. By analogy with quenched aluminum filmso11 it seems certain that these loops originate in the collapse of vacancy clusters formed during deformation. Metals, such as copper, having a relatively low-stacking fault energy would tend to produce Frank sessile loops (in practice tetrahedral defects with stacking faults on all (111) planes) rather than the glissile prismatic loops observed in aluminum. The manner in which these various defects affect the different aspects of fatigue behavior has not yet been fully investigated. The present work was designed principally to indicate whether tensile fatigue gives rise to hardening and softening effects similar to those associated with reversed stress fatigue, and with the hope of providing additional information on the contribution of point defects to fatigue deformation. Despite the uncertain ty often associated with the interpretation of resistivity data, i.e., the relative contribution of stacking faults and other defects, such measurements are conveniently employed to study point defect pheno-

Jan 1, 1962

By H. S. Price, D. A. T. Donohue

The system of equations describing displacement of a hydrocarbon liquid by a hydrocarbon vapor in a porous medium where mass transfer takes place between the phases is solved numerically for a variety of gas injection processes. Even though the method of solution is quite general, only systems with three hydrocarbon components are considered. Computer simulations of displacement processes wherein mass transfer between phases is both considered and neglected are compared, and it is shown that neglecting mass transfer can give pessimistic displacement efficiencies. INTRODUCTION The role of the gas displacement process in the recovery of petroleum has been subjected to a series of detailed analyses; as a result, a number of predictive models have been published in the literature. However, because of major simplifying assumptions, most of these models do not completely represent the physical system. As a result, the effect of making the simplifying assumptions is unknown. Therefore, a complete representation of this process — one without major simplifying assumptions —should lead to a fuller understanding of the process, and perhaps to methods of improving it. The general method of developing a model for two-phase fluid flow in a porous medium is to solve simultaneously the continuity equation, the energy equations and the equation-of-state for each phase under the prescribed initial and boundary conditions. For an isothermal system, the energy equations reduce to the momentum equation. Darcy&apos;s law. However, since natural gas is the vapor state of the reservoir liquid, interphase mass transfer may take place with concomitant changes in both the intensive and extensive thermodynamic properties of each phase. It is this phenomenon that has often been omitted in previous mathematical models. An additional relation, then, which accounts for mass transfer between the phases, must be included with the other equations to specify a complete model. Completely formulating the equations to be solved is not a difficult task1 but obtaining their solution has been intractable up to now. Availability of large-memory, high-speed digital computers now makes an attack on this formidable problem possible. This paper presents a preliminary study of the problem. Since this investigation is intended to be exploratory, it is restricted to the linear, horizontal, isothermal, two-phase viscous flow of oil and gas in an oil reservoir. In the early development of predictive models of this process, the reservoir system was considered as a unit and various forms of the material balance equation were proposed.2-4 Pressure and saturation gradients were then added in the Buckley-Leverett model.5 The Buckley-Leverett formulation considered the fluids to be incompressible; thus, the mathematical model reduces to a steady-state system. In the 1950&apos;s, studies incorporating numerical techniques were being published.6-9 These mathematical models differed in the efficiency of finite difference techniques, the inclusion or exclusion of capillarity or the number of space dimensions considered. To solve these nonlinear, partial differential equations, each phase was considered to be homogeneous with time; therefore, mass transfer between phases was neglected. The effect of mass transfer on the gas displacement process was first reported by Attra. 10 He simulated the one-dimension flow system by a series of cells in each of which the fluids were equilibrated during a time step. In addition, the pressure throughout the system during each time step was predetermined and constant-phase velocities were calculated according to the Buckley-Leverett incompressible fluid flow model. Welge et al.11 developed a model for the displacement of oil by an enriched gas where composition is considered to be a dependent variable. Fluid

By Arthur B. Cummins

Diatomite is a siliceous rock of sedimentary origin, which may vary in degree of consolidation, but which consists mainly of the fossilized remains of diatoms. These are microscopic algae of the order Bacillaria. Diatomite is a unique form of silica, there being nothing else found in nature or produced by the manufacturing arts, that has its characteristic physical structure. There are numerous sediments which contain some diatom residues, admixed with a substantial amount of other materials-clay, carbonates or silica. While these are classified as diatomaceous silts, shales, or mudstones, they are not properly diatomite, a designation which is restricted to material of such qualities that it is suitable for commercial uses. The terms diatomaceous earth and kieselgur are synonymous with diatomite. The expressions infusorial earth and tripolite are obsolete. Diatomaceous silica is a definition best used to distinguish the basic component of diatomite, that is, the substance of the silica shell itself and is the major constituent of beneficiated diatomite or processed diatomaceous products. Some highly indurated materials, such as cherty shale, porcelanite, and opaline cherts which have resulted from diagenetic changes cannot be considered as diatomite although they may have been derived therefrom. On the other hand, diatomaceous oozes or loose sediments consisting mainly of diatom residues with or without much organic matter are source materials in process of becoming diatomite. Composition and Properties Pure diatomite is composed of opaline or hydrous silica, with small amounts of associated inorganic components-alumina, iron, alkaline earths, alkali metals, and minor constituents, all of which may occur in solid solution or as an essential part of the opal complex. Crude diatomite on the other hand may contain variable amounts of organic matter and soluble salts, and the usual contaminants of sedimentary formations-particles of rockforming minerals, sand, clay, or carbonates. As occurring in nature, diatomite contains an unusual amount of free water, which may vary from 10 to 60 pct or more. Diatomite, in the dry deposits which are characteristic of most of the important world deposits, occurs as a lightweight, comparatively light colored, "chalklike" material. The apparent density (dry basis) in situ varies from 20 to 40 lb per cu ft. The structure may be either massive or finely stratified. The earth is highly porous, usually soft and easily friable. It is nonreactive with acids and may be tentatively identified by the above characterizations. Confirmation is by microscopic examination which readily reveals the nature of the material. In deposits which contain organic matter the appearance of the material is totally different. The color may vary from light tan or gray to brown, greenish or nearly black. There is frequently difficulty in distinguishing it in the field from peatlike materials, but the difference is readily apparent after calcination. Powdered diatomite or diatomite products have an apparent density (loose weight) of 5 to 16 lb per cu ft, wet densities of 10 to 30 lb per cu ft, specific gravities 1.9 to 2.35, index of refraction 1.42 to 1.48. Diatomite is essentially micro-amorphous, but does show some tendency toward orientation in structure after a cristobalite pattern. Amorphous silica has been considered as a random association of cristobalite crystallites, the size of which are only slightly larger than a unit cell.20 The prop-

Jan 1, 1960

By Joseph L. Gillson

BRAZIL has had an industry based on ocean beach deposits of heavy minerals containing monazite, zircon, rutile, and ilmenite for well over 40 years, but except at the very earliest period, prior to 1906, and again during World War 11, has this industry been at all comparable in size with similar operations in other countries. Limiting factors have been neither a lack of reserves nor lack of markets (except for zircon). Although poor local transportation and shipping facilities have handicapped the development in Brazil, these conditions were perhaps equally bad (when mining operations started) in the Indian State of Travancore, and in New South Wales and Queensland, Australia, in which states the principal production of beach deposits of heavy minerals has occurred. The outstanding restraints on the Brazilian industry have been the lower quality of the Brazilian minerals, the relative small size of individual deposits that were known until recently, the lack of interest of Brazilian investors in mining ventures, and the unfavorable climate for investment of foreign capital under Brazilian mining law. The lower quality of the minerals is indicated by the fact that the Brazilian monazite carries only 5 to 6 pct Tho2*, and the ilmenite 561/2 pct TiO2, whereas the corresponding Travancore minerals carry 9 pct Tho, and 60 pct TiO, respectively. The Brazilian zircon is a dirty brown color (which can be removed readily) as compared with the gleaming whiteness of the Australian zircon. An inadequate market for the abundant zircon that will be available in any operation in Brazil is certainly a heavy restraint, since otherwise it could be an important byproduct. The oxide of zirconia, baddeleyite, that has come from Brazil is from other sources.&apos; Since the Brazilian beach sands carry only a little rutile, that mineral has not been available as a valuable byproduct to help finance the operations. Substantial tonnages of rutile have been exported from Brazil. The sources of this mineral are stream placers and residual deposits over gneisses in the States of Goyaz, Minas Geraes, Ceara, etc. (Leonardos,&apos; and Chambers". With these handicaps, Brazilian production from beach sands has been marginal, and there has been only one consistent producer. This is a company, originally French, which was called Companie de Franco-BrazilliCne, but, with the downfall of France in 1940, became Brazilian under the name Monazita e Ilmenita do Brasil ("Mibra"). This company has operated several deposits in the vicinity of Guara-pary, in the State of Espirito Santo. Its office and plant has been at Guarapary. Recently a company called, "Fomil" (Fomento Monazita-Ilmenita) started operations. This company was organized by the Foote Mineral Co. of Philadelphia, and such share as a foreign company can hold under Brazilian law has now been acquired by the Lindsay Light and Chemical Co. of Chicago. When the writer went to Brazil in the fall of 1940, he found that no general survey of the beaches had been made except for a thorough study of part of the area by Abreu.4 The paper by Miranda6 had not then been written. The federal Geological Survey and Department of Mines knew only of the existence of the deposits in Espirito Santo south of Vitoria, and had a hazy idea that others might be found north of Vitoria. One deposit in Bala was known in Rio, but the larger one at Guaratiba was not known, although a Frenchman had prospected

Jan 1, 1951

By Joseph L. Gillson

BRAZIL has had an industry based on ocean beach deposits of heavy minerals containing monazite, zircon, rutile, and ilmenite for well over 40 years, but except at the very earliest period, prior to 1906, and again during World War 11, has this industry been at all comparable in size with similar operations in other countries. Limiting factors have been neither a lack of reserves nor lack of markets (except for zircon). Although poor local transportation and shipping facilities have handicapped the development in Brazil, these conditions were perhaps equally bad (when mining operations started) in the Indian State of Travancore, and in New South Wales and Queensland, Australia, in which states the principal production of beach deposits of heavy minerals has occurred. The outstanding restraints on the Brazilian industry have been the lower quality of the Brazilian minerals, the relative small size of individual deposits that were known until recently, the lack of interest of Brazilian investors in mining ventures, and the unfavorable climate for investment of foreign capital under Brazilian mining law. The lower quality of the minerals is indicated by the fact that the Brazilian monazite carries only 5 to 6 pct Tho2*, and the ilmenite 561/2 pct TiO2, whereas the corresponding Travancore minerals carry 9 pct Tho, and 60 pct TiO, respectively. The Brazilian zircon is a dirty brown color (which can be removed readily) as compared with the gleaming whiteness of the Australian zircon. An inadequate market for the abundant zircon that will be available in any operation in Brazil is certainly a heavy restraint, since otherwise it could be an important byproduct. The oxide of zirconia, baddeleyite, that has come from Brazil is from other sources.&apos; Since the Brazilian beach sands carry only a little rutile, that mineral has not been available as a valuable byproduct to help finance the operations. Substantial tonnages of rutile have been exported from Brazil. The sources of this mineral are stream placers and residual deposits over gneisses in the States of Goyaz, Minas Geraes, Ceara, etc. (Leonardos,&apos; and Chambers". With these handicaps, Brazilian production from beach sands has been marginal, and there has been only one consistent producer. This is a company, originally French, which was called Companie de Franco-BrazilliCne, but, with the downfall of France in 1940, became Brazilian under the name Monazita e Ilmenita do Brasil ("Mibra"). This company has operated several deposits in the vicinity of Guara-pary, in the State of Espirito Santo. Its office and plant has been at Guarapary. Recently a company called, "Fomil" (Fomento Monazita-Ilmenita) started operations. This company was organized by the Foote Mineral Co. of Philadelphia, and such share as a foreign company can hold under Brazilian law has now been acquired by the Lindsay Light and Chemical Co. of Chicago. When the writer went to Brazil in the fall of 1940, he found that no general survey of the beaches had been made except for a thorough study of part of the area by Abreu.4 The paper by Miranda6 had not then been written. The federal Geological Survey and Department of Mines knew only of the existence of the deposits in Espirito Santo south of Vitoria, and had a hazy idea that others might be found north of Vitoria. One deposit in Bala was known in Rio, but the larger one at Guaratiba was not known, although a Frenchman had prospected

Jan 1, 1951

By J. F. Havard

Gypsum is a useful industrial mineral found abundantly on the earth&apos;s crust. It is inexpensive to mine and process, and its calcined products have a wide range of readily controllable properties such as strength, density and setting time. It has proven to be such a useful material indeed, that ten American companies, operating some 57 calcining plants in 25 states in 1958, produced or imported in that year a total of 13,649,000 tons of the crude mineral valued at $39,361,000, which they then converted into manufactured products with a value of $329,070,000. Gypsum (CaSO4.2H2O) is calcium sulfate with two molecules of combined water, which are responsible for most of its useful properties. It is closely associated in most deposits with anhydrite (CaSO4), which contains no combined water and has limited commercial value in the United States. Man has long recognized the useful qualities of gypsum. It was utilized by the Egyptians in the construction of the pyramids and, later, by the Romans for important structures. Many of the ancient peoples prized gypsum for artistic and ornamental purposes, carving statuary from alabaster and making casts with plaster. The tabular variety, selenite, was used for windows, and the light transmitted through these windows reminded people of light from the moon (selene), hence the name selenite. The use of gypsum continued through the Middle Ages and into modem times. Benjamin Franklin was a famed exponent of gypsum because he applied ground gypsum to clover fields in the form of large letters which later read, in the more luxuriant growth, "land plaster used here." Gypsum is still used as an effective conditioner for some soils, but in recent decades, particularly in North America and Europe, it has become much more important as a major material for the building industry. Description Gypsum and anhydrite are closely associated minerals. Gypsum is found in a number of forms: massive rock gypsum, alabaster, selenite, satin spar, and gypsite. Anhydrite is found as massive rock or as smaller bodies or isolated crystals included in gypsum. Massive Rock Gypsum comprises most of the commercial gypsum and occurs as a sedimentary rock, interbedded in most places with shale, limestone or dolomite. This rock is soft and crystalline. Its color is white or shades of gray, pink, yellow, brown or other colors. Alabaster is a pure, compact and fine-grained variety suitable for use in sculpture or turning into artistic forms; it may be white or selected for attractive coloration. Selenite is gypsum crystallized in flat, transparent, flexible foliated plates, found in clays or in surface vugs in gypsum. Satin Spar is a fine silky fibrous variety with the axes of the crystalline fibers perpendicular to the vein or joint in which it has formed. Gypsite is an earthy mixture of gypsum with clay and sand in secondary formations; it is sometimes useful as a soil conditioner and has been used in making base-coat plasters. Pure gypsum contains 20.9 pct combined water, 46.6 pct sulfur trioxide (SO3) and 32.5 pct lime (CaO). Standard specifications (American Society for Testing Materials Designation C 22-50) read that minimum purity for material to be called gypsum is 70 pct CaSO4.2H20. Most of the commercial gypsum is 85 to 95 pct pure as produced. Impurities in

Jan 1, 1960

By Oscar Johnson

The industry has been canvassed for information on methods of handling grinding steel at milling plants, an important subject overlooked in most descriptive articles on milling plant arrangements. The data collected are offered in this paper as a guide to designers and planners who have loading and storage problems to solve. WITH capacities of milling plants expanding from a few hundred tons per day to many thousand, replenishment of grinding media is an important phase of mill operation. Information on this aspect of milling procedure, solicited from several mining companies, is summarized here. At International Nickel&apos;s Copper Cliff concentrator the normally strenuous job of changing rods is considerably simplified by the use of the Garrow rod charging machine, Fig. 1. The overhead crane, Fig. 2, brings a bundle of rods, weighing four to a ton, to the loading platform of the machine, positioned in front of the mill. The rods roll one by one down the slight incline of the platform onto a conveyor which sends them into the mill. A modified version of the Garrow machine, Fig. 3, is used at the Federal mill of St. Joseph Lead Co. An overhead crane places the portable steel structure in position in front of the discharge end of any one of the five 9x12-ft rod mills. It then raises a bundle of about twenty 3-in. rods to the discharge platform of the charging machine. The rods are 11 ft 7 in. long and weigh about 278 lb. By tripping a lever the operator allows one rod at a time to roll onto the inclined rollers. A slight push by the operator sends the rod smoothly into the mill. The Union Miniére du Haut Katanga rod charging machine, Fig. 4, is mounted on a pair of wheels at the forward end with swiveling castors at the back for steering it to position for use or storage. Wheels are equipped with locking brakes to maintain the machine in position while it delivers rods to the mill. The device is made in two parts. The first consists of the base, which carries the supporting wheels, grooved rollers, and drive. The other part serves as the rod deck, which can carry up to six 3-in. x 12-ft rods. A short boom built integral with the base reaches through the mill trunnion and delivers the rods into the mill barrel. Three grooved guide rollers ,are provided to receive the rods from the sloping charging deck. One rod at a time is fed to the rollers and thus delivered into the mill. Two of the rollers are driven by 11/2-hp motor through a V-belt drive. The third roller is driven off the first by a single V belt in a groove below the rod groove and on the same center line. Rods are delivered to the charger by an overhead crane in bundles of three to six as needed. The power is supplied by cables plugged into power outlets, suitably located near the rod mill discharge end. The Oliver Iron Mining Co. uses a rod charger, Fig. 5, suspended from a monorail by cables. It is constructed .of structural steel and has two decks, each capable of carrying five rods of 4-in. maximum diameter. The rods ride in grooved free-turning rollers. Legs extending down from the mill end of the mechanism act as supports when the unit is ex-

Jan 1, 1955

By H. W. Hockin, D. r. Brandt, R. H. Walsh, P. L. Dietz, P. R. Girardot

New Jersey, Florida, and Canadian ilmenites were reduced with hydrogen or coke under various experimental conditions and the phase changes occurring in the ilmenite upon reduction have been studied by microscopic examination of polished sections and by X-ray diffraction. The products formed were dependent upon the type of ilmenite, temperature, time and reducing agent. Of the reducing agents, hydrogen was the more effective at lower temperatures. 1 HE possible utilization of ilmenite as a source of both iron and titanium has resulted in the development of a number of methods for the separation of the iron and titanium content. Slagging processes as currently used in Canada are typical of such methods. Somewhat less attention has been given industrially to the reduction of the iron content at less than the slagging temperature. Although references maybe found to such work, in general only one type of ilmenite, either natural or synthetic, has been studied by each author. We have attempted to draw some relationship between the results of experimental reduction and the type of deposit from which the ilmenite was derived, as evidenced by phases occurring in the ores and in the reduction products. Ilmenite ores having from 27 to 61 pct titanium dioxide were included in this study and in each case reduction was carried out at such temperatures that only limited coalescence of the particulate iron product occurred within the ilmenite grains. The history of the individual ilmenite samples and the temperature of reduction were found to determine the occurrence of various phases and the mode of distribution of the iron. REVIEW OF EARLIER WORK ON REDUCTION One of the earliest references to the reduction of ilmenite at less than the slagging temperature was made in 1917.&apos; The metallic iron produced was_____ leached out by the action of dilute sulfuric or hydrochloric acid, to leave a product high in titanium dioxide. Subsequent to this, numerous patents2-&apos;? and other references13"21 have appeared concerning reduction of ilmenite by carbon, hydrogen, carbon monoxide, methane, coal gas, water gas, or the like in the absence of fluxing agents. Mineragraphic examinations were not reported, and in the main, the only examinations made were chemical analyses. However, in two cases3,13, titanium suboxides were reported in the products and in one case2&apos; rutile was reported, in addition to metallic iron. Both were identified by X-ray diffraction. While reductions in the absence of fluxing agents were generally followed by either a wet or dry chemical process for removal of the metallic iron, a Canadian source17 reported removal of the metallic iron by magnetic separation. By the addition of fluxing agents during reduction, the metallic iron has been coalesced into "pearls." Each reference to such a process23-28 has shown that the coalesced iron could be removed by magnetic or gravity means after the product was crushed. In the absence of fluxes, the coalescence did not generally occur. The major part of the present study has been limited to reductions without fluxing agents in order to determine the primary reactions of naturally occurring ilmenites. Titaniferous iron ores have also been studied,29-33 17, l9 their reduction having been used as the basis of a commercial process for beneficiation of such ores in Norway29 and more recently considered in the United States34,35. The ease of reduction of titaniferous iron ores relative to that of hematite or magnetite has been referred to,33 with the conclusion that the more

Jan 1, 1961

By J. R. Long, T. R. Graham, R. S. Dean

ALTHOUGH considerable information has been published concerning manganese additions to the aluminum bronzes, these data refer principally to the two-phase alloys containing 8 to 11 pct aluminum, with some incidental information on the single-phase alpha solid solution alloys. Strauss1 gives an excellent review of the literature on aluminum bronzes up to 1927 and a bulletin2 of the Copper Development Association brings the bibliography up to 1938. The most extensive work on manganese addition is that of Rosenhain and Lantsberry,3 who investigated alloys ranging up to 10 pct aluminum and up to 10 pct manganese, and presented data on the physical properties of sand-cast, chill-cast, and several wrought alloys. The greater portion of the work, however, concerns alloys ranging from 7 to 10 pct aluminum in the cast condition and sheds little light on the properties of wrought single-phase alloys. Corson4 notes that alloys containing 10 pct manganese and 4 pct aluminum are not hardenable by heat-treatment, while one with 15 pct manganese and 5 pct aluminum can be hardened, but he gives no tensile data on it. In fact, no systematic study of the properties of single-phase wrought alloys containing substantial amounts of manganese has been reported. It should also be noted that most of the investigators worked with alloys containing significant amounts of iron and silicon, and that these impurities, whether intentionally added or accrued from the raw materials used in the preparation of the alloys, may be expected to have a direct bearing on the resultant properties. In the work on alloys made with electrolytic manganese, the Bureau of Mines has undertaken an investigation of the copper-manganese-aluminum system for the purpose of establishing the constitution and properties of high-purity alloys. In a recent paper5 the authors reported a metallographic investigation of the alpha solid solution area and the adjoining fields of the copper-manganese-aluminum system up to 50 pct manganese. This study established the alpha-phase boundaries at 50° temperature levels from 400° to 850°C. It was found that the addition of manganese to copper-aluminum alloys decreases the solubility of aluminum in the alpha phase (Fig I), curving the boundary toward the copper-manganese base line. The greatest change occurs in the first 20 to 25 pct manganese, which decreases the solubility of aluminum to approximately 4 pct. With larger amounts of manganese the alpha boundary tends to parallel the copper-manganese binary. At 1300°F and higher,

Jan 1, 1947

By M. A. Torcaso, P. Raimondi

To study mass transport in systems simulating oil recovery processes, different porous media were saturated with a mobile (carrier phase) and a stationary phase. Slugs of carrier phase containing a small amount of solute were displaced with pure carrier phase. By analogy to the chromato-graphic processes, the velocity of the solute can be predicted from a knowledge of the partition coefficient and the saturation provided that equilibrium between the two phases exists. Equilibrium was found to exist for different porous media, solutes and rates. The conditions were varied over the range normally encountered in the laboratory and in the field. The longitudinal dispersion of a solute undergoing interphase mass transfer was also investigated. INTRODUCTION The production of hydrocarbons by gas cycling, enriched gas drive and C02 or alcohol displacement involves, among other factors, relative motion between two phases and compounds, hereafter called solute, which are soluble in both phases. The solute is carried forward by the faster flowing phase at a lower velocity than the average velocity of that phase. Retardation of the solute is caused by chromatographic absorption and desorption in the slower flowing phase and by the degree of departure from equilibrium. At equilibrium the concentration of solute in the two phases can be related by the equation* CSw = K Cso ,............(1) where C, and C are the concentration of solute in the aqueous and oleic phases respectively and K is the equilibrium ratio, or partition coefficient. Displacement theories must contain an explicit assumption with regard to equilibrium, i.e., whether the compositions can be related by Eq. 1. The existance of equilibrium depends, in general, on the relative velocity between the phases. Unfortunately, other factors such as gravity segregation and viscous fingering, also depend on velocity. For this reason, whenever effects of rate on displacement were observed,2-4 it was practically impossible to discern what caused them — lack of equilibrium or the factors mentioned above. Equilibrium between phases has been the subject of extensive studies in fields such as extraction or chroma to graphy. It has received only small attention in flow through the type of porous media encountered in oil production.5 For this reason a method was developed which makes it possible to study the movement of a solute as it is affected by rate, type of porous media, partition coefficient and carrier phase, but in the absence of segregation or fingering. The information obtained enables one to determine when the assumption of equilibrium can be made. Briefly, the method consists of (1) saturating the core with a mobile and an immobile phase, (2) injecting a slug made up of the same fluid as the mobile phase and a small concentration of mutually soluble solute, (3) measuring the lag and the peak height of the slug at arrival and (4) correlating these variables with fluid properties such as partition coefficient and mixing constants of the medium. PROPOSED MECHANISM The principles of chromatography are combined with the equation of longitudinal mixing to predict the velocity of a solute slug compared to the bulk velocity and the peak height of a slug.6-9 The equation so obtained is valid under equilibrium conditions only. Therefore, a comparison between experimental and predicted results will give a measure of departure from equilibrium. This work was done with either the oleic or the aqueous phase being immobile. For simplicity, the following development is based on the case where the oleic phase is immobile. However, the treatment is the same in either case.

Jan 1, 1966

By N. J. Grant, B. C. Giessen, R. Koch

The system Nh-Ir was investigated over the complete concentration range by metallography and X-my techniques, using forty one alloys. The solubility limits of terminal and intermediate phases and the solidus temperatures were determined. Five intermediate phases were found: a Nb3Ir, cubic, Cr3O type; tetragonal, ofecr thorhomhic, isostruc-turn1 with (ta-Rh); and a Nhlr3. cubic, AuCu, type. a Nb3lr and a Nbfr3 melt congruently; three eutectic and three pentectic reactions occur. The phase diagram of the Nb-Ir system had not been fully treated in the literature; only surveys of intermediate phases were found.1"5 In this study, the details of the phase boundaries were investigated as well as the crystallography of the intermediate phases. EXPERIMENTAL METHODS The experimental procedures such as arc melting of powder compacts, heat treatments, solidus measurements, X-ray, and metallographic observation were identical with those used in the work on the Nb-Rh phase diagram.&apos; They will therefore not be repeated here except where the conditions differed. The purity of the niobium powder was as stated in Ref. 6; the iridium powder of 99.9+ pct purity from J. Bishop and Co., Malvern, Penn., did not contain impurities exceeding 100 ppm, except rhodium (200 ppm). The melting points and vapor pressures of both elements are very similar. This fact contributed to a very small weight loss on melting and facilitated preparation of homogeneous alloys. As shown in Ref. 6 for Nb-Rh, no oxygen pick-up exceeding 200 ppm had to be considered; this was regarded as valid also for Nb-Ir. A total of forty one alloys were used in the determination of the phase diagram; their concentrations are shown in Fig. l, which presents the phase diagram. The concentration limits as determined by the weight-loss method averaged <0.2 at. pct, and never exceeded 0.5 at. pct. Heat treatments were carried out as described in Ref. 6. Depending on the concentration, only tantalum, tungsten, or iridium containers were employed, avoiding oxide crucibles altogether. Alloys from 0 to 25 and from 65 to 100 at. pct Ir were homogenized at 2095°C for 15 hr, intermediate compositions from 25 to 65 at. pct Ir for 65 hr at 1780°C. A typical annealing-time schedule is presented in Table I. Solidus points were measured as described in Ref. 6 with the modification that samples rich in niobium were held between pieces of tantalum foil and samples of high iridium concentrations were held between rhenium platelets or in iridium wire. After each run it was ascertained metallographically that no reaction with the holder had occurred. Rhenium was selected as holder material after it had been shown in separate tests that the melting points of Re-Ir alloys rise continuously from 2440°C. Metallographic examination was carried out as described in Ref. 6, and the same procedure and etchants were used successfully. While metallographic discrimination between a Nb3lr and o was easily possible, X-ray diffraction was necessary to separate al and ct2. X-ray powder patterns were taken and evaluated as for Nb-Rh6 yielding the error limits indicated in Table 111, to be introduced later. For the determination of the invariant reactions and phase boundaries, the same techniques as for Nb-Rh6 applied. The general accuracy of invariant concentrations is regarded as somewhat higher than for Nb-Rh due to the small slope of most solvus lines.

Jan 1, 1964