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By W. R. Webb, M. O. Peterson

WHEN men drive haulage equipment ranging up to 22 tons in an open pit operation, they must live with the realization that their safety is dependent upon the machines they drive and how well they operate them. The hazards inherent in their jobs must be recognized, met, and defeated. It comprises a never ending struggle toward perfection-an almost un- obtainable goal. The Jones & Laughlin Benson Mines, at Adirondack State Park in New York, created a safety program which resulted in only one three day lost time accident from April 1948 to April 1952. At the very start of the program, management of the open-pit operation recognized the hazards existing at Benson. The program was designed to meet each danger. With a knowledge of the problem faced, the process of minimizing each facet was planned along lines of maintenance of equipment and training of personnel. Its success is evident. In the ever-present struggle, care and maintenance of machines and application of experience to new equipment design are mainstays. Truck Haulage Benson produced 2.9 million tons of crude iron ore and 1.6 million tons of waste in 1951. To do the job, truck mileage reached 500,000 miles. The tremendous mileage emphasized to safety planners, the fact that the more work done, the greater the possibility of risk in haulage operations. Instrumenting the aim of the safest equipment possible is a methodical servicing program. Like other segments of the drive, the servicing program is based on greater production with fewer accidents. Every truck is serviced at least once per eight-hr shift. Examination includes inspecting and tightening wheel studs, checking tires, steering apparatus, lights, brakes, wipers, heaters, fire extinguishers, and refueling. A running history of the equipment's operating life is kept in the form of service and maintenance records. Machine operators are constantly on the alert for malfunctioning of units. At the first sign of trouble the truck is returned to the garage for exchange. No truck functioning incorrectly is kept on the line, regardless of its shift check schedule. The program resulted in a reduction of the number of costly overhauls and cut down the number of haulage accidents. Miscellaneous Mobile Equipment Auxiliary units, operating within the pit, have presented definite safety problems. The highest accident rate in the pit occurred on trucks carrying water and bits to the churn mills. The weight and awkwardness of bits and drill stems, combined with remote delivery points were direct causes of numerous accidents. Here, the problem has been one of equipment handling, rather than haulage. All air compressors for secondary drilling are truck mounted, facilitating mobility. In addition to making it easier to move the equipment, truck mounting has eliminated many of the hazards connected with relocating machinery. By making air compressors independent of other units, drilling operations have been speeded up considerably. Unseen rocks in the path of moving vehicles are a constant source of tire damage. At Benson the problem has been met by supplying each loading crew with a bulldozer for cleanup operations. The pitman directs the dozer operation, and when truck drivers back into loading areas, he serves as an extra set of eyes. Modern Truck Garage Provides Drive-Through Service Simplicity is the essence of any preventative maintenance program. At Benson, a modern garage, with a drive-through service bay simplifies servicing. Shift inspection of the 22-ton haulage units is accomplished with minimum delay and maximum thoroughness. Major repair work and periodic overhauls are done in the repair section of the truck garage. Crane facilities for handling heavy assemblies ease the job and add to the safety factor. Other mobile machinery,

Jan 1, 1952

By A. T. Aldred, K. M. Myles

The vapor pressure of chromium over solid V-Cr alloys has been measured by the torsion-effusion method in the temperature range 1450" to 1650°K. The chemical activities as well as the free energies, entropies, and enthalpies of formation of the alloys have hem computed from the vapor-pressure data. The activities of both chromium and vanadium exhibit fairly small negative deviations from Raoult's law over the entire composition range. The values of the excess entropies and the enthalpies of formation found at 1550°K are considered in terms of the changes in the clzaracteristic properties of vanadium and chromium that occur upon alloying. RECENT interest in the theory and properties of transition-metal alloys has shown the need for relevant thermodynamic data. The present investigation of the V-Cr system was undertaken as part of a more general study of thermodynamic properties of transition-metal alloys. The system was chosen because of the reported complete solid solubility of the components at all temperatures1 and because the difference in magnitude of the vapor pressures of vanadium and chromium allowed a simple effusion technique to be used. The torsion-effusion method was employed to minimize compositional changes in the alloys during the experiments. EXPERIMENTAL Equipment. The torsion-effusion apparatus, shown diagrammatic ally in Fig. 1, consists of a torsion system suspended inside a vertical vacuum chamber whose lower end is surrounded by a high-temperature vacuum furnace. An auxiliary optical lever and screen are used to determine the angle of rotation of the effusion cell. The torsion fiber is an annealed, high-purity, tungsten wire usually between 0.003 and 0.007 cm in diameter and about 43 cm long. The wire supports a concave mirror and a rigid tantalum connector tube. The effusion cell is fastened to the lower end of the connector tube by a dovetailed yoke and har- ness arrangement. The cells, which are 1.27 cm in diameter and 4.4 cm long, were made by electron-beam welding tantalum endcaps onto a 0.025-cm-wall tantalum tube. The two orifices, formed by drilling, have similar areas ranging from 0.011 to 0.031 sq cm. The noninductive sheath-type furnace consists of a single-phase tantalum heating element 6.35 cm in diameter, 15 cm high, and 0.013 cm thick; the element is completely surrounded by radiation shields in an evacuated chamber. The power system includes a 17-kva self-saturating saturable core reactor with an integral magnetic amplifier and a water-cooled, 15-kva, step-down power transformer with a multitap secondary. Temperatures are controlled to within ±1/2o at 1600°K by means of a unit that includes a reference voltage source, a dc electronic null detector, a current-adjusting proportional band relay, and the self - saturating reactor. At 1650°K the temperature variation within the cell, vertically and horizontally, is 3/4oK. Unwanted motions of the torsion system are damped by the movement of an aluminum vane, which is mounted on the connector tube, between the poles of an electromagnet. When not in use the magnet is withdrawn and rotated 90 deg to prevent its interaction with the rotation of the system. Measurements. The vapor pressure, p, is re-

Jan 1, 1964

By Mark J. Klein, Robert A. Haggins

The pesence of a small amount of oxygen was found to cause significant grain growth restraint in 99.99 pct Ag. This behavior does not seem to be due to the presence of an oxide dispersion, but instead, to be related to the existence of minute amounts of oxygen m solid solution. In the amounts necessary to cause the observed effects it was found that oxygen migrates with extreme rapidity, probably along extended structural imperfections, such as dislocations and grain boundaries. A number of years ago, hastton' observed that the presence of small amounts of oxygen caused a retardation of grain growth in silver. He attributed this behavior to the formation of a fine dispersion of oxide particles by the internal oxidation of trace impurities. More recently, wood2 also found that oxygen caused grain growth restraint in copper. Experiments using both copper and a dilute solution of aluminum in copper led to the conclusion that the effects observed in copper were due to oxygen in solid solution, rather than an oxide dispersion. During the course of a study of the influence of several solutes on the recrystallization of Silver, the presence of minute amounts of oxygen was found to exert a very significant influence on grain growth. The experiments reported here were undertaken to determine whether the grain growth restraint observed in silver due to the presence of oxygen is related to oxygen in solution or to an oxide dispersion. Because of the difficulty in measurement and control of the very small oxygen concentrations causing the observed effects no attempt was made to treat the data in a quantitative manner. EXPERIMENTAL PROCEDURE AND RESULTS Silver of 99.99 pct purity was melted and cast into slabs in a vacuum of better than 0.1 p. These slabs were reduced 50 pct by cold rolling to a thickness of approximately 2.5 mm. Samples cut from this material were annealed in vacuum for a series of different times at 803°C. Another group of samples was similarly annealed in air. This temperature is well above the recrystallization range for silver of this purity (150" to 200°C). The mean grain diameter of these samples was measured, both in the center and near the edge, using the line-intel-cept method, and is shown as a function of annealing time in Fig. 1. The grain size in the centers of the samples annealed in air was found to be larger than that of the surface regions, while the grain growth behavior of the edge and center regions annealed in a vacuum was approximately the same. he edge measurements were taken at a distance of 0.2 mm from the surface.) A few samples were annealed in nitrogen. Their behavior was identical to that of the vacuum-annealed samples. Samples annealed in oxygen had approximately the same grain growth behavior as those annealed in air, leading to the conclusion that this behaviouer is due to oxygen. The microstructure of a sample annealed in air at 803" for. 30 minutes is shown in Fig. 2. The smaller grain size near the surface is characteristic of the iir-annealed specimens. Possible causes of this grain growth restraint in the air-annealed specimen are the formation of an im-

Jan 1, 1962

By M. R. Annis

Drilling mud rheological and gel property changes due to elevated temperatures frequently cause problems in drilling deep wells. A laboratory investigation of the effects of time, temperatures up to 3001; and mud composition on these properties was made with concentric-cylinder, rotational viscometers of the Farm type. The viscometers were sealed from the atmosphere to prevent dehydration of the sample. Gel strengths were found to be more sensitive than viscosities to changes in temperature and mud cornposition. The high-temperature gel strengths of bentonitic clay drilling fluids were not predictable from low-temper.atl4t-e measurements. At high temperatures, [lie clay flocculates. The floccu-lation temperature depends on the concentration and type of solids in the mud and the degree of chemical defloccula-tion. As the bentonite content of a mud increases, floccrrla-tion temperature decreases. Lignosulfonnte treatment raises the flocculation temperature. To minimize adverse high-temperatrrre effects on mud properties, the mud should be maintainted at minimum solids content, properly treated with. a defloccullant which is stable at the maximum ten?perature encountered and maintained at a pH high enough to insure activation of the deflocculant for the duration required. The Methylene Blue Test for cation exchange cnpacity of a clay was found to be a useful guide in deter.niinirig when a mud contains a dangerously high clay conWnt. INTRODUCTION In drilling a well it is desirable, for several reasons, to know the effects of time and temperature on the rheological and gel properties of the drilling fluid in the hole. Problems associated with drilling fluids normally occur down-hole: so it is reasonable to be interested in the properties of drilling fluids at the conditions which exist down-hole. It has long been observed that high pump pressures are often needed to start circulation after a trip and that the "bottom-up" mud that is circulated back to the surface is usually more viscous than it was before "cooking" at the bottom of the hole for several hours. Burk-hardt' showed that a knowledge of rheological proper-ties of muds under down-hole conditions is necessary to predict pressure surges. He showed that the viscosity of a mud greatly influences the magnitude of pressure surges and the likelihood of lost returns. McLean et aL~ showed that the rheological properties of a mud under down-hole conditions are very important to cementing operations. This paper presents data showing the effects of time and temperature on rheological and gel properties of water-base drilling fluids. Measurements of gel strengths and rheological properties were made with two different concentric-cylinder rotational viscometers of the Fann type. One was the conventional six-speed viscometer modified to operate at temperatures up to 350F and at the vapor pressure of the liquid at test temperature. The other viscometer was newly designed to operate at temperatures up to 500F and pressures up to 1,000 psi. Tests with both instruments were made under essentially the same operating conditions. The new viscometer is shown in Fig. I. In this investigation, great emphasis has been placed on the rheological properties of clay suspensions, since clays are largely responsible for a mud's thixotropic and gel-

By A. D. Rich

The term "bleaching clay" or "bleaching earth," as used in the oil industries, refers to clays that in their natural state, or after chemical or physical activation, have the capacity for adsorbing coloring matter from oil. There are three common types of bleaching clays: fuller's earth, activated clays, and activated bauxite. Fuller's earth, or naturally active clay, is prepared from bentonites (see Chap. 5) that possess natural activity. It is not activated commercially; in fact, earths of this type ordinarily do not respond satisfactorily to acid activation. Fuller's earth is prepared in pulverized as well as granular form for use in the contacting and percolation processes, respectively. Acid-activated clays also are of bentonitic origin. The basic raw clay, however, is of a type that has a very low natural activity but is highly activable by treatment with mineral acid. Commercial acid-activated clays generally possess several times the decolorizing power (bleaching efficiency) of the best quality of fuller's earth. The former are prepared commercially only in the pulverized grade because of the difficulties in obtaining a satisfactory granular product, and hence are used only in the contact process. Activated bauxite is made by heat-treating bauxite ore, which in its natural state has very little natural activity. The commercial product is prepared in granular form for use in the percolation process on petroleum oils. For the most part, bleaching clay is used commercially in the decolorization of animal, vegetable and petroleum oils, fats and waxes. It is applied in two ways: (1) by the percolation method and (2) by the contacting method. Percolation refers to the passage of oil through a bed of granular clay whereas contacting refers to direct agitation of oil and pulverized clay followed by removal of the clay from the oil by filtration. In either case, the decolorizing effect is obtained by intimate contact between the liquid oil and the solid adsorbent. Petroleum oils are treated commercially by either the percolation or the contact process. Animal and vegetable oils are treated by the contact process only. Composition The raw clays from which both fuller's earth and acid-activated clays are prepared are composed of hydrous aluminum silicates containing varying quantities of magnesium, iron, calcium and other elements. These raw materials are usually nonswelling bentonites derived from volcanic ash or lava by weathering and hydrothermal chemical reactions. The bentonites have as their chief mineral constituent montmorillonite, which has the formula [(OH)4Si6A14O20•nH2O], according to Grim. (See Chap. 5, ref. 6, p. 91.) The underlying reasons are not fully known for the natural activity of the fuller's earth type of clay and its usual failure to further activate with mineral acid in contrast to the natural inactivity of the activatable type of clay. However, it may be said that the bentonites that are responsive to the acid-activation treatment generally have not undergone any drastic metamorphism. The chemical composition is not a reliable means of discrimination between a nonactive, a naturally active, and a nonactive but activable clay, therefore it is not possible to forecast the ultimate quality of a clay on the basis of the raw-clay analysis alone. Table 1 gives typical analyses of representative clays of the foregoing classifications.

Jan 1, 1960

By Donald E. Grimes

In conjunction with Inland Steel&apos;s development of lead-bearing steels possessing improved machin-ability because of tellurium and/or selenium additions, it was decided to determine liquidus and solidus temperatures in the Pb-PbTe-PbSe sub-ternary system. With the exception of alloys in the PbTe-PbSe system, it is believed that no previous study of this subternary has been performed. Thermal analysis was employed in a general survey of the subternary. In addition to PbTe, PbSe, and pure lead, ten ternary compositions were selected at intervals of ten at. pct. Sixty-gram alloys were prepared by sealing an appropriate mixture of the elements in quartz crucibles with a central thermocouple-well under a vacuum of less than 10 p. All three elements were 99.999+ pct pure with only trace impurities detected by spectroscopic examination. After the alloys had been heated at least 20°C above the liquidus in a Kanthal furnace, cooling and heating curves were obtained. Two or more cooling curves were employed both for the determination of each alloy liquidus and for the solidus of those al- loys containing greater than 50 at. pct Pb. Cooling rates were 0.5° to 3.5°C per min during the 5 min immediately prior to the start or end of solidification. For those ternary alloys containing 50 at. pct Pb, the solidus was determined from heating curves. Temperatures were measured with a Pt/Pt-10 pct Rh thermocouple which was calibrated in the same apparatus against the freezing points of zinc (A. D. MacKay—99.999 pct), antimony (A. D. MacKay-99.999 pct), and copper (ASARCO—99.999+ pct) both before and after the experimentation. The only interruptions in the continuous strip-chart recording of the temperature occurred for brief periods at significant points of interest when direct readings were made with a Rubicon Type B potentiometer sensitive to * 1 µv. The average liquidus and solidus temperatures obtained in this investigation are listed in Table I together with probable errors based on the accuracy of the thermocouple calibration and the reproduci-bility of the data. No chemical analyses of the alloys were performed because the synthetic or as-charged compositions were felt to be reliable. The melting points obtained for PbTe (924.7° ± 0.7°C) and PbSe (1084.0° ± 0.6°C) compare favorably with recent findings of other investigators.&apos;-&apos; As indicated in Table I, both the liquidus and solidus temperatures increase as selenium replaces tellurium for a constant atomic percent lead. As a result, the ternary liquidus and solidus temperatures for a given percent lead lie between the corresponding binary temperatures published in the literature. It should be noted that those ternary alloys containing 50 at. pct Pb exhibit a relatively narrow liquid-plus-solid region (<80°C) when compared with alloys containing greater than 50 at. pct Pb. Alloys with 60, 70, or 80 at. pct Pb not only have a much wider liquid-plus-solid region (>500°C) but also exhibit considerably lower and approximately constant solidus temperatures which thus form a virtually isothermal solidus "plane" slightly below the melting point of pure lead (327.3°C). For these alloys

Jan 1, 1965

By S. J. Rothman, L. T. Lloyd

S. J. Rothman and L. T. Lloyd (Argonne National Laboratory)— Hagel&apos;s paperz0 discusses the question of the mechanism for self-diffusion in bcc transition metals. Recent work21"23 has led us to agree with him in reabandoning the ring mechanism in favor of a defect mechanism, most likely vacancies. On the other hand, we think that Hagel&apos;s attempt to group together all self-diffusion in bcc transition metals is wrong. We prefer the scheme of Peart, Graham, and omlin," who separate them into two groups. One group contains the anomalously behaved metals P titanium,&apos;, y uranium, and perhaps zirconim.&apos; The other group contains a iron," this alloy was held at 1800°C for 2 hr before quenching, its structure was all a. B. C. Giessen, I. Rump, and N. J. Grant (Authors&apos; reply)—We very much appreciate the discussion by Deardorff and Kato regarding the a to /3 transformation temperature of hafnium. In the W-Hf program, as well as in a current study of the system Cr-Hf, standard precautions were exercised against contamination, including vacua of less than 10"5 mm Hg and a weight control check of all specimens to insure an impurity rise of less than 100 ppm. Following receipt of the above discussion, a revision was made in the annealing process. Arc-cast specimens were etched with a 10 pct HF-90 pct HNO solution until 1 mm of surface, including a possible oxide film, was removed. Annealing was done in a hafnium container which provided a long diffusion path for gaseous contaminants. Finally, the heat treating time was shortened. Structural changes were noted to occur quite slowly. A 99.5 at. pct Hf alloy showed 70 pct /3 after 30 min at 1700°C and was 100 pct /3 after 10 min at 1715°C. After 24 hr at 1740C, the alloy was found to be 10 pct/3. This change is due to contamination; it was estimated that it corresponds to an increase of 60°C in the transformation temperature over a 24 hr period. The corresponding change in 30 rnin would be slight. Using the same hafnium as in the above publication, and three new alloys at 98, 99, and 99.5 at. pct Hf, the transformation temperature was indicated to be 1715" 15°C. Since this hafnium contained 4.4 at. pct Zr, a correction of 40 5C, based on an assumed approximately linear transformation temperature curve, must be made for pure hafnium. This yields a value of 1755 20°C in good agreement with Deardorff and Kato&apos;s value. Because the slope of the boundary is small, this permits a good extrapolation, and we regard the W-Hf alloys as well suited to check the Hf transformation temperature. niobirn,&apos;&apos; and molybdenum,22 whose activation energies correlate with the melting temperature and whose Do values follow Zener&apos;s predictions.28 We have no quarrel with Hagel&apos;s placing chromium into the second group; we disagree with his interpreting our data to make uranium fit into that group. Hagel considers that the measurements of self-diffusion in uranium below about 950°C represent combined volume and grain boundary diffusion. This contention is based on the curvature of the penetration plot for our 891°C run,4 which also has a nearly straight line plot of log c vs x. Hagel has extrapolated these characteristics to our 803.5C run and fitted his Arrhenius plot for self-diffusion in y uranium to our four highest temperature points only. We think this is wrong for the following reasons.

Jan 1, 1963

S. Tandanand, Twin Cities Mining Research Center, U. S. Bureau of Mines As an addition to the fine reviews on drilling presented in the foregoing papers, we feel it would be appropriate to mention briefly some work in this area by the U. S. Bureau of Mines. The Bureau has had under way for several years at its Twin Cities Mining Research Center studies directed toward a better understanding of basic drilling mechanisms. The work includes drillability investigations with diamond rotary, and with percussive drilling systems, as well as fundamental studies of rock behavior under drill bit types of loading. Results of our work to date have contributed the following to the state of the art. MECHANISM OF ROCK FAILURE-Rock fragmentation through use of mechanical energy systems, including drilling systems, consists of two major components-machine and rock. The two components are related to each other by their functional behavior and their resultant motion which the components mutually influence. Forces in the systems are transmitted directly to the bit which in turn induces stresses in the rock. When the induced stresses exceed the strength of the rock, the rock fails resulting in penetration. Rock strength is a function of the forces applied to the rock. Stresses under a drill bit, regardless of bit configurations, are essentially compressive, resulting in a condition where the rock has the highest resistance to failure. The ratio of principal stresses induced under drill bits is an indication of the mode of failure in the rocks. Initially, compressive stresses under the drill bit cause rock to undergo inelastic deformation. The impression observed at the first stage of crater formation under the drill bit shows that rock is no longer elastic. Associated subsurface failure at this stage precedes total rupture which subsequently appears at the rock surface. Thus, explanation of crater formation, by applying theory of elasticity alone, is likely to be over-simplified. ENERGY VERSUS VOLUME OF ROCK REMOVED-Experimental results show that energy per unit volume of rock removed is constant for a particular rock and bit type. Rock offers a definite resistance to penetration, depending on the method of the energy application; this may be defined as the drilling strength of a rock. Energy consumption in a drilling system may be divided into two components: 1) Energy required to move the machine parts; and 2) energy consumption in breaking rock. Component 1 is dependent on the type of the machine. Component 2 is dependent on the strength properties of rock and the efficiency of the bit in rock cutting. The sum of the energy required in both components determines the total energy required in breaking rock. Our work in this area has included consideration of both diamond and percussive drilling systems. PENETRATION RATE-For a drilling rate expression to be useful in predicting field performance, it should include the operating characteristics of the drilling machine. Eq. 37, for example, is simply a statement of the fact that the drilling rate is determined by the power output of the machine (2pNT) and the power requirements to break the rock in the hole (AER). In order to predict the performance of a particular drill and the effect, for example, of the rotary speed, on the drilling rate, R, Eq. 37 must be modified to include the

Jan 1, 1967

By J. F. Evers, S. Sadiq, F. W. Preston, G. W. Swift

Proper scaling of unsteady-state flow in laboratory gas reservoir models can be achieved if the permeability/fractional porosity ratio is less than 0.5 md. Porous media meeting this specification can be obtained from mixtures of sand and Portland cement provided (1) the water/cement ratio is in the range of 0.35 to 0.40, (2) the sand/cement ratio is in the range of 1/1 to 2/1, (3) the sand grain size is in the range of 48-100 to 18-28 mesh, (4) the mortar curing time is 7 days or more and (5) the cured mortar is dried under vacuum to reduce the temperature level employed during the drying process. The areal homogeneity of the mortars tested is reasonably good, although significant trends in vertical permeability were noted. The Klinkenberg and non-Darcy coefficients of mortar are such that proper scaling of these effects in the laboratory model could be expected. INTRODUCTION A long term deliverability prediction for a gas well is generally based on data determined from flow tests that are of short duration relative to the producing life of the well. These data, together with an estimate of gas reserves in place, form the basis for establishing the parameters of the mathematical model used to predict performance at future times. Results obtained from a mathematical model represent only an interpretation of the physical process being modeled. Experimental verification of the production process from discovery to abandonment is needed where production occurs under carefully controlled conditions. Ideally, one might consider such an experiment to be conducted in the field. Even if the cost of such an experiment could be justified, the time required would make it impractical to consider. However, if the time scaling problem could be handled properly, an experimental model of the gas reservoir production process could provide the necessary data to study the mechanisms of the production process in a reasonable time period. An experimental model has been designed and constructed using the data of this study as a basis. The model reservoir system consists of one producing well located at the center of a right-circular cylinder of porous material. Ten to 15 observation wells are located at strategic offset positions from the producing well. These wells, and the producing well, are fitted with pressure transducers so that the pressure-time history can be recorded at various radial and azimuthal positions in the drainage area during the entire production life of the system. Time is scaled in the model so that the time required to produce gas from discovery pressure to abandonment pressure is about 2 hours. This compares with a 20-year producing life in the model&apos;s field counterpart and gives a time scale factor of approximately 1:100,000. DESIGN CRITERIA To establish design criteria for the experimental model, the reservoir is considered to be a finite right-circular cylinder of radius rr, and height h with a producing well of radius rw located at the center and completed through the producing formation. This reservoir consists of a porous medium which has a uniform permeability k and gas porosity and the gas contained in the reservoir has density p, viscosity µ and molecular weight M. Initially, the pressure at all points within the reservoir is uniform at po. and the reservoir temperature is T. Since the reservoir production process has been demonstrated to occur in two distinct transient modes for either Darcy or non-Darcy flow,l it is

By D. K. Bose, C. K. Gupta, K. U. Nair

A new approach to processing an indigenously available low grade molysulfide concentrate by chlorination with elemental chlorine in presence of oxygen is reported. Recovery of nickel and copper values associated with the sulfide concentrate by suitably treating the residue obtained after chlorination is also reported. In the chlorination process, a gaseous mixture of chlorine and oxygen in the volume ratio bf 2:5 has been passed at 1.66 x 10- 5 m3/s for 1800 s over a 0.01 kg batch of molysulfide concentrate at a temperature of 573°K. Most of the molybdenum has been volatilized as molybdenum oxychloride which has subsequently been extracted in water. The molybdenum value from the aqueous solution has been recovered in the form of calcium molybdate (CaO.MoO3) by treatment with calcium chloride (CaCI2). In an alternative processing scheme, the molybdenum rich solution has been treated with an oxidizing agent (K2S20f.J) and allowed to boil to recover a major portion of the molybdenum value in the form of molybdic oxide (MOOS). The spent charge obtained after molysulfide chlorination has been mixed with about 1 wt % sodium chloride and heated at 773K under an oxygen atmosphere. The reacted mass has been water-leached to yield a nickel-copper bearing solution with limited iron. The process liquor appears to be well suited for further processing by known hydrometallurgical recovery processes for nickel and copper. In the conventional process of molybdenum extraction, the molysulfide concentrate (-59% Mo) is first subjected to roasting to produce molybdic oxide. The oxide is then further processed in sequential steps involving vacuum distillation, ammonia leaching, and calcination to higher purity prior to hydrogen reduction to metal. In India there is at present some small tonnage production of molysulfide concentrate from a byproduct recovery plant of the M/s. Uranium Corp. of India Ltd. (M/s UCIL), Bihar. Efforts are being made at this laboratory to process the low grade fraction of the concentrate which contains sulfides of copper, nickel, and iron; quartz; and chlorites. Here, the conventional routes involving roasting and vacuum distillation appear unsuitable to produce an acceptable quality of molybdic oxide at high recoveries. Formation during roasting molybdates of some of the impurities present in the sulfide concentrate make subsequent vacuum distillation less efficient. In view of these problems, in earlier work reported from this laboratory the low grade concentrate has been processed hydrometallurgically to P. produce calcium molybdate. Starting from this molybdenum intermediate, processes have also been developed for the production of molybdenum and ferromolybdenum. Chlorination as an alternative to roasting for metal sulfides has been drawing considerable interest. The high reactivity of chlorine, the relatively low temperature of operation, the suitability of application to low grade resources, the convenience of recovering sulfur in non-polluting form, and the purity of chlorides which are separated by distillation all favor chlorination. In recent years, considerable work has been reported on the chlorination of common metal sulfides. In the field of molybdenum extraction from its sulfide resource, use of chlorination technology has been rather limited. Senderoff and Labrie3 were the first to chlorinate molysulfide concentrate with elemental chlorine at about 823°K to molybdenum pentachloride for use in the electrolytic preparation of molybdenum. The only other reported work, by Haver, Uchida and Wong, involved reaction between molysulfide and chlorine at 673°K to recover sulfur. The reaction products were, however, identified as molybdenum pentachloride and sulfur monochloride.

Jan 1, 1979

By J. H. Jackson, P. D. Frost, C. H. Lorig, L. W. Eastwood, A. C. Loonam

R. S. BUSK*—I wish first to congratulate the authors of this paper both for the work done and the presentation of that work. We have also been working on this type of alloy development, but any technical contribution I might have is better reserved for a separate paper which is planned in the near future. However, I would like to insert a word of caution. The alloys described in this paper are still very much in the laboratory stage. There still remains the quite vexing problem of property stability at slightly elevated temperatures which must be solved before the properties quoted can be effectively utilized. These alloys are extremely interesting and I am confident that the problems can be solved. However, the present existence of those problems must not be overlooked. I have one question with regard to the work-hardening test. If the work harden-ability of magnesium is compared to aluminum using a more standard test such as the Meyer Analysis the magnesium is found to work harden the more rapidly. Is the test developed for this work truly a work-hardening test or a measure of something else ? J. H. JACKSON (authors&apos; reply)—I am sure we appreciate the comments of Mr. Busk and we are pleased that the Dow Chemical Co. has also undertaken work in this field. It is a big field. We, of course, are continuing our research for the Navy Bureau of Aeronautics, since, as clearly shown in the paper, the alloys are not completely developed. With regard to Mr. Busk&apos;s comments on the relative work-hardenability of aluminum and magnesium, the comparison we cited in the paper was intended merely to show that the results obtained by our method of testing were independent of the yield strength of the materials. We believe that this test method afforded a rough indication of the work-hardenability of the magnesium-lithium base alloys. It is not known whether this method affords greater or less accuracy than the Meyer Process, which is based upon a hardness-test impression. It is quite possible, since work-hardenability is a function of metal purity, that our results, obtained for commercial aluminum and magnesium, would be different if high-purity metals had been used. A. C. LOONAM—Lithium has some very interesting effects on magnesium. The paper showed that even small percentages increased ductility. These small amounts changed the axial ratio of the hexagonal magnesium from 1.624 in the pure metal to 1.606 in the saturated alpha solution, a value close to that of titanium, which has a ratio of 1.601. You will recall an article in the January, 1949, issue of the Journal of Metals where it was stated that titanium can be cold-rolled over 90 pct without any significant edge cracking. At 4.9 or 5 pct lithium, a change begins in crystal structure—from a hexagonal close packed to body centered cubic. There are two phases over a short range of lithium content, but at 10 pct the structure becomes completely cubic. The melting points of alloys in this range of lithium content are relatively high. Alloys even up to the six ratio have melting points above 500°C; this represents a relatively small reduction in melting point from pure magnesium itself. The magnesium-lithium system has a number of very interesting characteristics. This is only a very small part of the story. J. H. JACKSON—I would like to remind you that Mr. Loonam is one of the authors of this paper, and the fact is that this work is based on many of his ideas. I am sure we appreciate his additional comments in this discussion. R. LEITER*—I am interested in Fig 19 in which Mr. Jackson compares

Jan 1, 1950

By B. S. Butler

AN understanding of mineralizing solutions and how they carry and deposit metals is of prime importance to students of ore deposits. Lindgren states: "The whole problem surely is very complicated. One difficulty is that we know so little about the stability field of ore minerals."1 Lindgren further states: It is believed that they [the solutions] were in small part oxidized to sulphates, for instance, but in large part they were composed of hydrogen sulphide, alkaline sulphides and various halogen compounds. Doubtless, however, free carbon dioxide was present. Becker&apos;s view of the double sulphides as important constituents of the solutions probably holds good. In the fourth edition of Mineral Deposits2 Lindgren had changed his views somewhat: From the work of Day, Allen, Shepard, and others, it would seem probable that many of the volcanic gases are acid when given off but are in unstable equilibrium, and could not have preserved this acid character after having been long in contact with the surrounding rocks. It is believed that they were in small part oxidized to sulphates, for instance, but in larger part they were composed of hydrogen sulphides, alkaline sulphide, and various halogen compounds. Doubtless, however, free carbon dioxide was present. Becker&apos;s view of double alkaline sulphides as important constituents of the solution probably holds good. The writer wonders if progress would not result from an attack on the problem in steps, the steps to contribute to the attack on the whole. The initial step would deal with the simpler bodies of supposed magmatic (hydrothermal) origin, that is, those composed essentially of silicates, oxides, sulfates, and sulfides. The following discussion attempts to develop one step of a method that was proposed on a more comprehensive scale in 1929 by the writer and W. S. Burbank.3 The accompanying partial table (Table I) of the electromotive series is from a table distributed by Merck & Co. Inc., manufacturing chemists, prepared in turn from Fundamental Chemistry.& The electromotive arrangement brings together elements that in hypogene ore deposits occur: 1) in oxygen combination only; 2) in combination with sulfur as well as with oxygen; and 3) as sulfides, arsenides etc., and as native metals, see Table 11. The writer clearly recognizes that he is not qualified to discuss the formation of ore deposits as a chemical problem, but he feel that some of the relations that are met by the geologist can well be stated with the hope that the chemical explanation will be forthcoming. By consideration of a group including mainly the elements oxygen, hydrogen, sulfur and iron, complications are avoided, especially with elements of the lower electromotive group. The results can only contribute to the solution of the problem, not to the completion of it. The pH and Eh of the solutions and also temperature probably determine what minerals form. The mineral groups that contain elements high in the electromotive series are alumino-silicates, titanites, simple silicates, spinels, oxides, carbonates and sulfates, in all of which the elements are combined with oxygen. These groups are also recognized as the general order of temperature at which the minerals start to form, see Table 11. At low temperature are sulfides, arsenides, antimonides, sulfo-salts, and native metals, in all of which the elements are characteristically not combined with oxygen. The intermediate temperature group contains elements that form both oxygen compounds and sulfur compounds.

Jan 1, 1957

By T. R. Ingraham

When aluminum sulfate was decomposed in an evacuated apparatus and the sample cooled, Q alumina was found. The thermodynamics of the decomposition reaction were resolved by measurements of the total pressure of SO3, SO2, and O2 generated over the sample at various temperatures. The results were correlated with other published data to calculate the rmges of thermodynamic stability of the various compounds involved. The thermal decomposition of aluminum sulfate was studied by Wijhler, Pluddeman, and Wöhler1 and by Warner and Ingraham.2 The results of both studies were critically reviewed by Kellogg,3 who observed that "each set of data shows considerable scatter and strong curvature on a plot of log pso3 vs 1/T".3 He agreed with Warner and Ingraham2 that both the discrepancy in the two sets of results and their curvature may arise from the indefinite properties of the particular form of A12O3 which is formed during the decomposition. While studying the thermal stability of other sulfate systems, we had noted the presence of nonequilibrium oxide properties in both the cobalt4 and manganese5 systems, but neither had shown any appreciable curvature on a logPSO, vs 1/T relationship, and the data from both systems agreed reasonably well with prior work. It therefore seemed reasonable to reexamine the technique which had been used in our earlier work on aluminum sulfate.2 The principal difference was that a tightly compacted pellet had been used for the earlier aluminum sulfate work, whereas a loose powder, contained in a platinum boat, was used for our work on other sulfate systems. In addition, a better technique had been developed for dehydrating the samples. From work done on the nickel system,6 we had become aware of the highly protective nature of some sulfate layers on their oxjdes, and hence of the necessity of providing a large surface area of P3e sample when equilibrium was to be attained in a reasonable time. That observation suggested that perhaps a steady state, rather than equilibrium, had been reached in the earlier work on aluminum sulfate. This paper reports a repetition of the experimental work with large, finely divided samples of anhydrous aluminum sulfate. APPARATUS AND PROCEDURE The apparatus used in the experimental work was described in earlier papers.2,7 The source material was Anachemia reagent-grade Al2(sO4)3 - 18H2O which was first partly dehydrated by heating at 400°C for 48 hr and then completely dehydrated by repeated baking of an aluminum sulfate-oleum slush to dryness at 450°C. ? Alas was prepared by decomposing some of the sulfate in a muffle furnace at 800° C overnight. Approximately equal amounts of the 7) alumina and aluminum sulfate were used in the experiments. The finely divided samples were handled under dry box conditions, and in addition some of the aluminum sulfate was decomposed in the apparatus while it was under vacuum, to ensure its complete dehydration prior to sealing the apparatus. The samples were heated to a series of constant temperatures on both increasing- and decreasing-tem-perature programs. Two to three days were required to obtain steady readings of the total decomposition pressure on an increasing-temperature program, and 5 to 6 days on a decreasing-temperature program. Three samples were examined on both programs. Within experimental error, the results for each sample and each program could not be distinguished.

Jan 1, 1969

By C. A. Siebert, S. H. Bush

Isothermal temper-embrittlement studies were conducted on a 5140 steel at various temperatures for times as long as 3000 hr. Specimens from the embrittled steel were subjected to impact tests, metallographic examination, microhardness, and lattice-parameter measurements. SEVERAL of the steels in the low alloy group are subject to a pronounced decrease in impact energy if held within, or cooled slowly through, a range of temperatures below the lower critical. This phenomenon, known as temper embrittlement, is quite pronounced in the chromium steels of which AISI 5140 is typical. This study considered the response of one heat of 5140 steel when embrittled isothermally at various temperatures for times as long as 3000 hr. Excellent reviews of the work done in the field of temper embrittlement have been written by Hollomonl and Woodfine.&apos; Both authors list the various theories which have been advanced to explain temper embrittlement. Some of the mechanisms considered were: 1—a transformation below 700°C; 2—an allotropic modification of iron; 3—precipitation from the ferrite of such compounds as carbides, nitrides, phosphides, or chromium oxides; 4—decomposition of retained austenite; 5—modification of special carbides; 6—grain-boundary segregation; and 7—selective distribution of carbides. The present study investigated the changes in hardness, Meyer&apos;s number, impact properties, micro-structure, and lattice parameter which occurred on embrittlement. Previous studies considered the influence of microstructure and of prior austenitic grain size3 on the response of 5140 steel to temper embrittlement. Equipment and Procedure All samples were taken from one heat of 5140 steel; the chemical composition of this steel was: 0.43 pct C, 0.86 pct Mn, 0.020 pct P, 0.019 pct S, 0.27 pct Si, 0.84 pct Cr, 0.10 pct Ni, 0.06 pct Mo, 0.10 pct Cu, and the remainder Fe. The material was received as % in. rounds. This stock was cut down to blanks measuring approximately 0.425~0.425~2.196 in. Heat Treatment: The rough blanks were normalized at 1600°F (870°C) for 1 hr, then austenitized at 1600°F (870°C) for 1 1/2 hr, and quenched into an agitated oil bath. The specimens were tempered at 1275°F (690°C) for 5 hr and water quenched. These tempered specimens were designated as the toughened state. Embrittling Treatments: The tempered bars were divided into sets and subjected to the various embrittling treatments listed in Table I. Temperatures from 750" to 1050°F were investigated for times of 1 to 3000 hr. Special tests to determine the effect of heating a short time at a higher temperature after long-time embrittlement at some lower temperature were also conducted. All specimens were water quenched at the end of the embrittling cycle, then ground and notched to obtain standard Charpy V-notch specimens. Impact Tests: The bars were fractured in a 260 ft-lb Charpy impact unit; specimens were fractured at temperatures ranging from —315°F to room temperature. Fixed temperatures used consisted of —315°F with liquid nitrogen, —115°F with dry ice and acetone, and 32°F with ice and water. Intermediate temperatures were obtained by suspending the bars in a jig over the liquid nitrogen, dry ice and acetone, or ice and water.

Jan 1, 1955

By James Kemp

PostScript to a paper presented at the New York meeting, February, 1915, and printed in Bulletin No. 98, February, 1915, pp. 129 to 154. The writer looked over the quarry with care in the search for fossils, having in mind shells or corals of fairly large size. In the brilliant summer sunshine, none were observed on the glaring white ledges. The impression was gained that none were present and the statement to this effect was made in the edition of this paper published in the Bulletin&apos; of the Institute for February, 1915, p. 136. On closer examination in the laboratory it has been discovered that the limestone itself is made up of minute organisms, which are clearly revealed by microscopic examination of thin sections. The principal component of the rock is a small foraminifer, 0.1 to 0.3 in. (2.5 to 7 mm.), of the genus Orbitoides, presumably an Oligocenic form. Figs. 1 and 2. illustrate it. The accompanying description has been kindly summarized by Marjorie O&apos;Connell, M. A., Curator in Paleontology in Columbia University, who first detected the evidences of organisms in the rock. Orbitoides kempi O&apos;CONNELL N. SP.1 The foraminiferan which makes up the Seboruco limestone is an Orbitoides of a Species new to North America. The only Orbitoides heretofore described from this country is 0. mantelli from the lower Oligocenic of the Gulf States. This form from Cuba, then, so different in all of its characteristics from the 0. mantelli, is of great interest as perhaps forming a basis of correlation over wide areas. The most closely related Species is 0. dispansa Sowerby, which occurs in the Nummulite limestone of the Eocenic of the Bavarian . Alps, in the Priabona beds of the lower Oligocenic of Massano, and elsewhere in Italy, as described by Gümbel.2 The age of the limestone in Cuba would thus Seem to be of upper Eocenic or lower Oligocenic age, probably the latter. The fossil has the form of a sphere Surrounded by a wavy rim of horizontal extent, the whole resembling two flat-brimmed, round-crowned hats placed base to base. The total extent of the Shell ranges up to 7+ mm., while the thickness of the central sphere is 2.5 mm. in one of the largest individuals. Like all of the other Species of Orbitoides, this form begins with a Single layer of chambers which multiply in one plane and assume a circular outline; but it is in the subsequent growth that the distinguishing specific characters appear, for the chambers at the central portion of the shell increase more rapidly than do those near the periphery and in consequence a Swelling is produced which finally gives the Spherical form which is so characteristic. The rim, on the other hand, shows little chamber-increase and remains thin. This is clearly Shown in the sections figured, where the central row of larger chambers forms the equatorial zone. Radiating from this row, in section, there appear, a number of solid cones alternating with broad reticulated ones. The solid cones mark the more dense structure forming the walls surrounding the reticulated or chambered cones. These appear upon the Surface as distinct pits, whereas the solid part appears as raised walls.

Jan 7, 1915

* Kennecott Copper Corp. gets Charles R. Cox as president on Jan. 1. Mr. Cox is resigning his position as president of Carnegie-Illinois to take the new post with Kennecott, left vacant by the death of Mr. Stannard in September. •The ECA signed a contract in December to advance X3,600,000 to Newmont Mining Corp. to aid development of lead and zinc mines in French Morocco. The funds are to be repaid in lead and zinc for the United States&apos; stockpile over a period of seven years. The mines are owned by the Societe des Mines de Zellidja, with which organization Newmont is associated. • Under the direction of John M. Brooks, Jr., general manager, the Matahambra mine in Cuba, will probably produce sufficient tonnage to make 4 million lb of copper per month during 1950. The grade is presently running between 7 and 10 pet. •S. H. Ash reports that the fatality rate per million-man-hr for the anthracite industry for 1949, through November, is 0.78. This is 15 pct better than that achieved during 1948, which was the lowest fatal injury rate in coal mining history. The first full year on record without a major disaster was recorded in 1949 (p. 34). •The Atomic Energy Commission has authorized the production of 200 lb of uranium metal for use under AEC license in non-Commission research projects. •A national survey of projected 1950 purchases of new machine tools, machine tool accessories, materials handling equipment, etc., just completed by the American Society of Tool Engineers reveals that, of the companies reporting, 80 pct state that they plan to buy either more equipment or the same amount as in 1948. • Armour Research Foundation is conducting investigations for the use of clay and shale deposits to make lightweight aggregates. The material is heated until it expands and forms material suitable for mixing with cement which it is hoped will be lighter, stronger, have better insulating qualities and will lower the cost of concrete. •In the first six months of 1949 the bituminous coal miners&apos; average hourly earnings were $1.94 -as compared with X1.392_ national average for all manufacturing. Average annual earnings of full-time employees in the bituminous coal mines in 1948 were $3387 as compared with $2809 for all industry. •LaSalle Business Bulletin reports: "year ends on a rising trend in industry and trade ... nearly record-breaking demand from almost all sources keeps business high... most indicators but little below postwar peak... forces keeping activity high arestill powerful--changes in general business conditions likely to be slow and moderate." •Office of Internal Trade of the Commerce Department requests that technical data significant to the national security which is to be sent outside of the United States be submitted to it for an official opinion on the desirability of transmitting such information. This voluntary compliance program is part of our national security control. • Blast furnace slag reduced to 12 to 16 mesh is being used for sanding track at the Mont Coal mines of Armco. The slag replaces silica sand which caused silicosis. It has proved so effective and cheap that tests are being made to use the slag for rock dusting.

Jan 1, 1950

By N. F. Fiore, M. C. Mangalick

DISLOCATION damping in single crystals is orientation dependent.&apos; If dislocations are distributed uniformly over all the slip systems in a crystal, and if each dislocation contributes identically to the damping process, then a damping loss or decrement 6 arises. In fact, however, for a crystal of axial direction (hkl), dislocations on certain slip systems are oriented to make a larger contribution to the damping loss than are dislocations on other slip systems. Thus the measuring damping, 6 (hkl) is proportional to an orientation factor (hkl), which weights the ability of each slip system in the crystal to contribute to the total damping. If it is assumed that dislocations are distributed uniformly on all slip systems, then for a given orientation of an fcc crystal this factor is determined2,3 by the three nonzero elastic constants Cll, C12, and C44 and the density p. In this communication measured values of elastic constants for two Fe-18Cr-Ni alloys are reported, and the dislocation damping results on two different orientations of each alloy are analyzed for orientation dependence. Elastic constants were determined by measuring the ultrasonic velocities of one longitudinal and two shear waves in (110) direction of the fcc crystals.4 Variation of velocities with the change in orientation is very small for (110) orientation,3 and so this direction is ideal for orientation factor and comparative damping measurements. Experimental Procedures. The nominal compositions of the alloys studied are given in Table I. These alloys were vacuum-melted and vacuum-cast from high-purity materials at U.S. Steel Applied Research Laboratories. The single crystals were grown by the modified Bridgeman technique. The specimens were homogenized at 1350°C for 20 hr, cut to shape and size with a spark cutter, and then annealed at 1100°C for 20 hr prior to use. In the KHz frequency range, the Marx composite piezoelectric oscillator was used to obtain the damping. The ultrasonic pulse technique was used to measure the ultrasonic velocities and the attenuation in the MHz frequency range. M.c.mANGALICK,-- StudentMemberAIME,formerly Research Assistant, University of Notre Dame, is now with Casting Laboratory, Chase Brass and Copper Co., Cleveland, Ohio. N. F. FIORE, Associate Member AIME, is Assistant Professor, Department of Metallurgical Engineering and Materials Science. University of Notre Dame, Notre Dame, Ind. This communication is part of a Ph.D. thesis presented by M. C. MANGALICK to the Graduate School of the University of Notre Dame. Manuscript submitted May 20. 1968. IMD Elastic Constants. Table I gives the values of the ultrasonic velocities. Values of C11, C12, and C44 calculated from these velocities are also given in Table I, and it is evident that there is very little variation in C11, C12, and C44 with nickel content. This slight variation may be attributed to inaccuracies in velocity measurements and practical differences in the orientations of the specimens. For example, in B the time interval for vl was 2.4 ± 0.05 sec giving an error in v1 of 0.235 x or 0.005 in. per sec. The elastic constants obtained by pulse technique were tested by calculating E<110>, Young&apos;s modulus for the (110) direction, from the equation: This value was compared with the value computed from the resonance bar measurements in which where fr is the resonance frequency and I, is the length of the specimen. In all cases, the values calculated from the ultrasonic velocity measurements

Jan 1, 1969

R,. P. JaRvis,* El Oro, Estado de México, México.—The practical problem raised by Mr. Wisser—that is, the determination of the lower limit of ore deposition, below which it is useless to look for ore shoots—is one of the most important in economic geology. He asks: "Can we learn to determine the position of such a line?" For individual districts, yes; but its determination has always been by empirical methods; that is by actually exploring the veins to such depths that the values drop below the economic limits. Usually the signs are plain enough that values have been bottomed without confirmation by the chemist or assayer. Most veins, when approaching their limit, begin to split into branches or stringers; the vein matter itself undergoes a change from "lively looking" rock to one that is dull and unpromising, the quartz, instead of having segregated into clean vein matter, has simply spread itself into the country rock, rendering this more siliceous but no richer—these, together with inclusions of the country rock in the vein, are all positive indications of the limit. Mr. Wisser seems disposed not to accept the law of cause and effect, which he calls "empiricism." He says: "Empiricism embodies an assumption perhaps not evident at first glance. It is this: that like effects spring from like causes and therefore necessarily have a common meaning." There can be no doubt as to the validity of this law, since it is the foundation stone upon which are built all inductive sciences, including economic geology. When demonstrable, proved facts become confused with inferences, as they seem to be generally in the paper under examination, no sound conclusions can be reached. Mr. Wisser has failed to give sufficient data covering the two vein systems which he cites as examples. Presumably they are situated in the Pachuca District of Mexico, but not everybody is familiar with the vein systems there in spite of the fact that it is world famous as a silver producer. Are these two systems separated some distance horizontally from one another and how far? He has given no estimate of the amount and kind of rock that has been eroded from over the present veins. His description of the two systems appears on page 100, beginning: "1. East-west veins," and ends on page 101, "they would lack spaces there in which to deposit." On page 101, with the paragraph beginning "On the other hand," he gives a picture of what he believes takes place in class 2 veins. The sum of this seems to be, according to Mr. Wisser&apos;s observations, that, in the east-west veins, class 1, there has been an invasion of an "altering solution," which I judge has been responsible for the formation of extensive "alteration haloes"; that these alteration solutions have followed along pre-existing fractures or fissures; and that after these alteration solutions finished their work the mineralizing solutions deposited the vein matter and metallic values. Mr. Wisser does not specify clearly what the "alteration haloes" consist of; in other words, what change the original rock has suffered, whether oxidizing, carbonating, or sulphidizing. If they came from depth they could not be oxidizing or carbonating, and in this case it is a bit

Jan 1, 1941

R,. P. JaRvis,* El Oro, Estado de México, México.—The practical problem raised by Mr. Wisser—that is, the determination of the lower limit of ore deposition, below which it is useless to look for ore shoots—is one of the most important in economic geology. He asks: "Can we learn to determine the position of such a line?" For individual districts, yes; but its determination has always been by empirical methods; that is by actually exploring the veins to such depths that the values drop below the economic limits. Usually the signs are plain enough that values have been bottomed without confirmation by the chemist or assayer. Most veins, when approaching their limit, begin to split into branches or stringers; the vein matter itself undergoes a change from "lively looking" rock to one that is dull and unpromising, the quartz, instead of having segregated into clean vein matter, has simply spread itself into the country rock, rendering this more siliceous but no richer—these, together with inclusions of the country rock in the vein, are all positive indications of the limit. Mr. Wisser seems disposed not to accept the law of cause and effect, which he calls "empiricism." He says: "Empiricism embodies an assumption perhaps not evident at first glance. It is this: that like effects spring from like causes and therefore necessarily have a common meaning." There can be no doubt as to the validity of this law, since it is the foundation stone upon which are built all inductive sciences, including economic geology. When demonstrable, proved facts become confused with inferences, as they seem to be generally in the paper under examination, no sound conclusions can be reached. Mr. Wisser has failed to give sufficient data covering the two vein systems which he cites as examples. Presumably they are situated in the Pachuca District of Mexico, but not everybody is familiar with the vein systems there in spite of the fact that it is world famous as a silver producer. Are these two systems separated some distance horizontally from one another and how far? He has given no estimate of the amount and kind of rock that has been eroded from over the present veins. His description of the two systems appears on page 100, beginning: "1. East-west veins," and ends on page 101, "they would lack spaces there in which to deposit." On page 101, with the paragraph beginning "On the other hand," he gives a picture of what he believes takes place in class 2 veins. The sum of this seems to be, according to Mr. Wisser&apos;s observations, that, in the east-west veins, class 1, there has been an invasion of an "altering solution," which I judge has been responsible for the formation of extensive "alteration haloes"; that these alteration solutions have followed along pre-existing fractures or fissures; and that after these alteration solutions finished their work the mineralizing solutions deposited the vein matter and metallic values. Mr. Wisser does not specify clearly what the "alteration haloes" consist of; in other words, what change the original rock has suffered, whether oxidizing, carbonating, or sulphidizing. If they came from depth they could not be oxidizing or carbonating, and in this case it is a bit

Jan 1, 1941

By Joseph J. Becker

RECENTLY the "oriented growth" hypothesis of recrystallization textures has been receiving considerable attention. According to this view, "whenever a new generation of grains is growing in a highly oriented matrix . . . one may assume . . . that from among available nuclei of a great variety of orientations those with suitable orientation relationship with respect to the matrix have by far the highest rate of growth (oriented growth) and will, therefore, predominate."&apos; This statement includes primary recrystallization of single crystals and of polycrystalline materials showing strong deformation textures as particular cases. While the phenomenon of oriented growth undoubtedly does operate, and may be of importance in coarsening or secondary recrystallization, the writer feels that its extension to primary recrystallization is a different matter. Several aspects of this phenomenon may be pointed out which are difficult to rationalize on the basis of oriented growth. In recrystallizing deformed single crystals of alpha brass, Maddin, Mathewson, and Hibbard2 found that the twin composition planes of the recrystallized grains were parallel to the three operative slip planes they observed, and not to the fourth octahedral plane. The writer&apos;s current work seems to indicate further that when only one or two slip systems can be seen to operate, the recrystallized grains are aligned only with those slip planes actually observed. This behavior could hardly be accounted for by oriented growth, because on the latter basis the recrystallized texture of a deformed single crystal should certainly have the same symmetry as the crystal itself. Growth rates could not be expected to distinguish between crystallogra- phically equivalent directions, unless the presence of a visible slip system vastly increases the growth rate in the appropriate direction. This seems unlikely. These relationships were observed by the writer only when considerable care had been exercised before annealing to etch away the effects of cutting out the centers of tensile specimens with a jeweler&apos;s saw and to etch off the ends of compression specimens. When these.precautions were not taken, nu-cleation inevitably appeared to occur at the saw cuts or at the ends, and the resulting orientations never showed a [111] rotation but appeared quite random. The provision of many nuclei of many orientations did not enhance the correlation, but destroyed it. Recrystallization textures are sometimes strongly dependent on annealing temperature, which would imply that the anisotropy of growth rates is a suddenly varying function of temperature. This might be regarded as unlikely. Recrystallization textures can be strongly dependent on the degree of deformation. If textures are to be explained by selective growth from among nuclei of all orientations, it is difficult to see how the recrystallization process could have any dependence whatever on the manner or degree of deformation. It is felt that the above points should be considered before the oriented growth hypothesis is applied to primary recrystallization, with the necessary complete divorce of the mechanism of recrystallization from the details of the deformation process. References 1P. A. Beck and H. Hu: Reply to discussion of their paper on Recrystallization Texture and Coarsening Texture in High Purity Aluminum. Trans. AIME, 188, 1057; Journal oF Metals (Aug. 1950) TP 29083. &apos;R. Maddin, C. H. Mathewson, and W. R. Hibbard, Jr.: The Origin of Annealing Twins in Brass. Trans. AIME, 185, 655; Journal of Metals (Sept. 1949) TP 26763.

Jan 1, 1952