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By Fred H. Poettmann

The vaporization characteristics of carbon dioxide in a League City natural gas - Billings crude oil system were studied at three temperatures, 38°. 120°, and 202°F and for pressures ranging from 600 to 8,500 psi. Variation of carbon dioxide concentration up to 12 mole per cent in the composite showed no effect on the equilibrium vaporization ratios (K values) of the hydrocarbon constituents or on the K value of carbon dioxide itself. It was shown that carbon dioxide is more soluble in crudes than in distillates which is contrary to the behavior of methane. A working chart of carbon dioxide K values is presented. INTRODUCTION The study of the equilibrium vaporization ratios of mixtures of paraffin hydrocarbons has been rather thorough.2,6,7,8,9 In the past few years considerable attention has been paid to the vaporization characteristics of the so-called noncondensable gases such as nitrogen, carbon dioxide, and hydrogen sulfide in mixtures of hydrocarbons. since they usually occur to some extent in most crude oils and natural gases.1,3,4,5 Knowledge of this behavior is useful to both the production and refining phases of the petroleum industry. This paper reports the equilibrium vaporization ratios (K's) of carbon dioxide in a mixture of League City natural gas and Billings crude oil, and compares them to those obtained in a natural gas-distillate system. The equilibrium vaporization ratios for the hydrocarbon components in this system had previously been studied by Roland.' In addition to the determination of the K values for carbon dioxide, the K values for methane and ethane were also determined in order to observe what effect, if any, the presence of carbon dioxide had on these K values. The concentration of carbon dioxide was also varied in order to observe the effect of this variable on the carbon dioxide K values. EXPERIMENTAL PROCEDURE The apparatus used in this study cotlsisted of a stainless steel equilibrium cell of about 2 liters capacity. The cell was mounted on trunions permitting rocking in a thermostatically controlled oil bath. Two high pressure valves fitted with steel tubing were mounted on the top of the cell. one was used for sampling the equilibrium gas phase and the other for sampling the equilibrium liquid phase by means of an induction tube within the cell. Stainless steel tubing from the bottom of the cell led to a mercury reservoir and manifold which was connected to a free-piston type pressure gauge manufac- lured by the American Instrunlent Ctr. and to a volumetric. putrip. The temperature of the oil bath was measured by means of a ralibrated mercury-in-glass thermometer. The recorded temperatures are believed to be accurate to ±0.5 °F. The pressures are correct to 22 psi. The crude oil used in this study was stock tank oil obtained from the Wilcox formation in the Billings Field, Noble County. Okla. The natural gas was obtained from the League City Field. Galveston County, Tex. The oil was treated with anhydrous calcium sulfate in order to remove the last traces of water. To insure a supply of constant composition gas at room temperature the cylinders of League City gas were cooled to about 30°F, inverted, and the condensed liquid was allowed to drain from the cylinders. The analysis of the gas and crude are tabulated in Table I. The carbon dioxide came from Pure Carbonic, Inc., and was .stated to have a purity of 99.5 per cent or better. The procedure used to obtain samples of the equilibrium liquid and vapor was similar to that employed by others making use of the rocking type equilibrium cell.6,7,8 The equilibrium cell was evacuated and calculated quantities of carbon dioxide, natural gas, and crude oil were charged to the cell to the desired pressure. In charging the equilibrium cell an attempt was made to maintain the ratio of the natural gas to crude oil as close as possible to that employed by Roland. After the cell was charged, samples of

Jan 1, 1951

By N. J. Grant, R. Nordheim

An extensive study was made of the aging characteristics of alloys based on the 80 pct Ni-20 pct Cr composition hardened with aluminum and/or titanium, each up to 4 pct. Aging was followed by means of hardness and hot electrical resistance measurements as well as by X-ray and microscopy. Stress rupture tests at 1500°F were utilized as a check on the predicted behavior. THE titanium and aluminum hardened Ni-Cr alloys, exemplified by Nimonic 80 and Inconel X, constitute one of the more important groups of alloys developed to meet the demand for materials retaining their strength at elevated temperatures. For service in the temperature range 1200" to 1500°F, these alloys offer high creep resistance. With increasing service temperature, however, the strength of the simpler Ni-Cr base alloys falls off rapidly so that above 1500°F there is a significant loss of strength. The present investigation was undertaken with the hope that a better understanding of the factors controlling the precipitation hardening of these alloys would make it possible to increase the useful service temperature range. Primarily this investigation involved the study of the effects of titanium and aluminum on the hardening and the subsequent softening at elevated temperatures. The titanium and aluminum contents were each varied between 0 and 4 pct by weight at a constant nickel to chromium weight ratio of about 4:1. (Except when otherwise stated, all compositions are expressed on a weight basis.) The major part of the investigation was confined to alloys with less than 0.06 pct C. Recently several papers dealing with the identity of the microconstituents in the titanium and aluminum hardened Ni-Cr alloys have been published. Using X-ray analysis of the residues from anodic dissolution, Rosenbauml was only able to identify carbides and nitrides in Nimonic 80 and Inconel X. However, since Rosenbaum worked with alloys in the hot rolled rather than in the aged condition, his results are inconclusive. Recently Hignett' reported that the hardening of Nimonic 80 was due to the controlled precipitation of Ni,(TiAl) having the cubic Ni3A1 structure. Taylor and Floydv-" published the results of an investigation of the nickel-rich corner of the Ni-Cr-Ti, Ni-Cr-Al, and Ni-Ti-A1 systems. In the Ni-Ti and the Ni-A1 systems the hexagonal Ni,Ti phase, 7, and the cubic Ni3A1 phase, -y', respectively, exist in equilibrium with the nickel-rich solid solution. The interatomic distances in the basal plane of Ni,Ti and the octahedral planes of the matrix are almost equal, thus explaining the Wid-manstaetten type structure formed when Ni,Ti precipitates from solid solution. When Ni:,Al precipitates from solid solution, it appears usually in globular form, often dispersed along rows corresponding to definite crystallographic directions. The 7 and phases are also the only intermetallic compounds which occur in the nickel ternary alloys with up to 25 pct Cr and 10 pct Ti or Al. Taylor and Floyd found that Ni,Ti takes practically no nickel, chromium, or aluminum into solution. Nial, on the other hand, dissolves a considerable amount of chromium and titanium and some nickel. Up to three out of every five aluminum atoms could be replaced by titanium in Ni,Al. This substitution caused a slight increase (less than 1 pct) in the lattice parameter. With respect to the effect of variation in the titanium and aluminum contents on the high temperature strength of Nimonic 80 type alloys, Pfeil, Allen, and Conway" reported that an 80 pct Ni-20 pct Cr alloy containing 0.20 to 0.30 pct A1 had the highest creep resistance when the titanium content was kept between 1.65 and 2.75 pct. Experimental Procedure The materials used for this investigation were electrolytic nickel, electrolytic or low carbon chromium, sponge titanium and 2s aluminum. The alloys were melted in an indirect carbon arc furnace under

Jan 1, 1955

By V. F. Hollister

The Queen Charlotte gold deposit (also known as the Specogna, Babe, or Cinola) was discovered in late 1970 by Efrem Specogna and Johnny Trico. They were prospecting along the trace of the Sandspit fault, and they sampled jarositic material that included veins from the fault zone. Their assays included some good gold values. They located the Babe Claims in 1971 and optioned them to Kennco Explorations Ltd. Kennco conducted stream sediment and soil geochem studies, geological mapping and drilling of 55.2 m (181 ft) in two drill holes. Kennco withdrew from the property, and by 1977, Cominco, Placer Development, Silver Standard, and Quintana Minerals had each successively worked on the deposit. Consolidated Cinola Mines bought the claims in 1977 and completed exploration of the deposit ultimately in a joint venture arrangement with Energy Reserves. Energy Reserves entered in late 1979, and by 1983, a total of 200 surface and 12 underground drill holes had been completed, totaling 28 600 m (93,832 ft). In addition, a 461.9 m (1515 ft) adit was driven in the ore body. Reserves published by Cinola aggregate 34 Mt (37 million st) of 1.7 g (0.060 oz) Au per tonne. All industry geologists working in the area agree that the Queen Charlotte gold is an epithermal gold deposit in porous volcaniclastic and clastic rocks that is genetically related to a Miocene-Pliocene rhyolite plug. The geologic description here follows the oral presentation made by G. G. Richards, J. S. Christie, and M. R. Wolfhard at a 1976 CIM meeting. Additional comments by the late C. S. Ney of Kennco Explorations are included with the Richards, Christie, and Wolfhard data to complete the geologic set- ting. The attached reprint by Champigny and Sinclair (1 980) provides additional data on the deposit. The Queen Charlotte (Babe, Specogna, or Cinola) gold deposit is located on Graham Island in the northern Charlotte Islands, at the fault boundary of the Skidegate plateau and the Charlotte lowlands. The Sandspit fault marks the physiographic boundary, and it is intruded by rhyolite porphyry at the deposit. Because displaced geochem anomalies, drain- age patterns, and topography suggest dextral and east side down movement for the fault, exposed east block rocks are younger than rocks west of the fault. The east block, which included the ore deposit, is a lowland largely masked by unconsolidated Pleistocene and Recent clastic rocks. Rocks west of the rhyolite plug, on the Skidegate plateau, are Cretaceous carbonaceous and calcareous shale unconformably overlain by a thin veneer of rhyolite tuff. The deposit is about 100 m (328 ft) above sea level. GEOLOGIC SETTING At the ore deposit, the Sandspit fault is a complex structure. However, lithologies on either side of the fault-controlled rhyolite porphyry plug are distinct. West of the rhyolite, the upper member of the Cretaceous Haida formation shale is the most common rock type. The member is composed of dark grey to black, poorly consolidated, and thinly bedded carbonaceous and calcareous shale. The sequence is silicified to an argillite or a hornfels near the rhyolite. West of the rhyolite porphyry plug, but not importantly involved in the mineralization, is a thin masking cover of rhyolite tuff. The tuff unconformably succeeds the cretaceous shale, but it is largely eroded in the mine area. East of the fault-controlled rhyolite porphyry plug is a thick section of conglomerate and sandstone of the Miocene- Pliocene Skonun formation. The ore body occurs within the coarse clastics, the rhyolite intrusive as the western boundary. Ore is entirely contained within the clastics. Original permeability of the clastic rocks was a major control for ore deposition and alteration, and for that reason, the Skonun formation is described in greater detail. The Skonun formation clastics unconformably overlie Haida shale. The Skonun is at least 300 m (984 ft) thick in the mine area, where it trends northerly and dips easterly 15º to 25º. The sequence is about 62 percent conglomerate, 3 1 percent coarse arkosic sandstone, and 7 percent interbedded siltstone and sandstone. Contacts between adjacent beds are generally sharp. Stratigraphic correlations between drill

Jan 1, 1985

By R. R. Angel

Drilling rate is a parameter that should be considered in determining the volume requirements for air and gas drilling. The use of past methods which ignore the effects of the solids content upon the pressure and velocity of the annulus flow stream can result in undercalculation of the required volurne by as much as 50 per cent. A vertical-flow equation is presented for determining volume requirements. This equation includes the effect of the solids that are transported up the annulus in the flow stream by incorporating the drilling rate as one of the parameters. The effect of down-hole temperature on required circulation rates is also ana-lvzed. A simple approximate method of determining volume requirements is presented. This method is more accurate than the methods used in the past. Hole cleaning difficulties are analyzed for a recent air drilling job where past methods indicated that - excess air was being used. Sample curves of calculated boitom-hole pressures are presented for air and gas drilling in several hole sizes. INTRODUCTION In certain areas the use of air or natural gas as a circulating medium for drilling oil and gas wells is becoming a common practice. Large increases in penetration rate and bit life are achieved through the use of these media in preference to mud or water. Drilling rates as high as 90 ft/hr have been obtained in shales. The importance of maintaining adequate circulation rate is generally recognized; however, much disagreement exists among drilling operators as to what constitutes "adequate" circulation rate. In quarry drilling, where annular velocities can be accurately determined, an annular velocity of 3,000 ft/min of standard air is required for best results in rocks having approximately the same density as those commonly penetrated in drilling oil or gas wells'. Although this standard air velocity has proven satisfactory for quarry drilling, some oil and gas well drilling operators believe that an equivalent annular velocity of more than 4,000 ft/min is required; others believe that as little as 2,000 ft/min . is sufficient. Much of this disagreement results from determining the required circulation rates with methods which fail to incorporate the drilled solids in an equation which is applicable to vertical flow. Hughes Tool Co. Bulletins No. 23' and 23-A3 present data for determining circulation rates based on the Weymouth formula. These data do not include the drilling rate as a parameter and, therefore, neglect the effect of the solids being transported up the annulus. In spite of this apparent defect and the fact that the Weymouth formula is not applicable to vertical flow, the Hughes data have well served the drilling industry in many areas and are important and timely contributions to the science of air and gas drilling. The Hughes data purposely omit a correction for increasing down-hole temperature. At slow drilling rates this effectively compensates for the use of a formula which is not valid for vertical flow; however, volumes determined by the Hughes method are not sufficient to support rapid drilling rates at moderate and great depths. For example, Phillips Petroleum Co.'s Cauthorn "D" No. l in the Vinegarone field for Val Verde County, Tex., was air drilled from 1,500 to 9,300 ft using a compressor delivering 1,400 cu ft/min. The 8 3/4-in hole was drilled with 5-in. drill pipe, and drilling rates as high as 90 ft/hr were obtained between 7,000 and 9,300 ft. No water or caving hole was encountered. At 7,728 ft it was necessary to wash-out 60 ft of cuttings to reach bottom after a trip to change bits. At 8,130 ft a twist-off occurred and the drill col-lars were stuck in drill cuttings. These difficulties indicate that the 1,400 cu ft/min of air was not sufficient to keep the hole clean. Hughes data indicates that 1,180 cu ft/min is sufficient to produce an annular ve-

Jan 1, 1958

By H. Carroll Weed

By caving a block into the workings of its open pit and using the block as an ore transfer, the lnspiration Consolidated Copper Co. has solved a transportation and sizing problem, making possible a great expansion of open-pit methods as applied to Inspiration ore-bodies. FROM 1915 to 1948 the entire production of Inspiration Consolidated Copper Co. was supplied from underground mining. The sole method used was block caving. Underground haulage and hoisting facilities were designed and geared to large-scale production. Beginning in 1948 open-pit mining was substituted for block caving in a portion of Inspiration's Live Oak orebody. The idea proved so attractive that before the Live Oak pit had come into production, another pit on the Colorado orebody (now the Thornton pit) had been laid out and stripping started. It should be noted that these orebodies were not new and the entire program was one of changed methods of mining. Since part of these orebodies had already been mined by block caving methods, it must be recognized that haulage levels had been established under the area or adjacent to it. The orebodies lay on the south side of Inspiration Ridge, while the shafts, crushers, and treatment plants are all on the north side of this ridge. The existing main crushing plant was designed to take a maximum of 12-in. material, and all ore was sized to this dimension by passing through grizzlies in the stopes. In the original planning for open-pit work much thought was given to the transfer of ore to existing underground levels for haulage and hoisting from the regular shafts. If this could be done the necessity of crossing the ridge could be eliminated. Final decision called for cutting a road through the ridge, installation of a primary crusher at an elevation of 3968 ft on the north side of the ridge, and railroad haulage with existing facilities to the main coarse crusher. This decision was brought about by the difficulties of properly sizing and transferring to underground haulage large tonnages of coarse breaking oxide which lay on the upper benches of the proposed pit. Trucking over the ridge on a 7 pct grade would give a cheaper and more flexible operation in handling this material. The benches in the pits are laid out at 50-ft inter-vals and designated according to elevation above sea level. The lowest bench in the original pit was laid out at 3500-ft elvation. All haulage roads are on a 7 pct grade and a vertical lift of 468 ft was considered about the maximum economically possible from a cost standpoint. After 2 years' operation the advantages of pit mining, both from the standpoint of costs and flexibility of operation, became more and more apparent. Studies were then started to develop the extension of open-pit mining to more of the ore reserve than had been planned originally. The idea of transfer raises was again explored. Obviously, as elevation of the pit was lowered, shorter transfer raises would be needed to reach the main haulage levels. Transportation from the lower elevations to the rim of the pit by belt conveyor or skip hoisting was also considered. However, it was recognized that sizing would be required both for conveying and regulation of feed size to the main crusher plant. This would necessitate a fixed or portable crusher located somewhere in the pit. It was known that the sulphide ore at the lower elevations was softer and easier to break than the overlying oxide of the upper benches. This sulphide ore is very suitable for grizzly sizing. Calculations indicated that for ore mined on 3650 elevation, costs for trucking to the primary crusher, crushing, and delivery by railroad to the coarse crusher would equal costs for dropping the same material to the 600 level, hauling underground, and hoisting directly to the coarse crusher bins, provided a suitable method of sizing and transferring could be developed. Above 3650 elevation costs would favor surface haulage; below they would favor underground haulage. The idea of caving an underground block from the 600 haulage level directly into the bottom of the pit

Jan 1, 1954

By Gearge C. Wallick

This paper describes experimental procedures for the calibration of capillary tubes to be employed as comparison standards in gas flow-rate measurements and considers several types of flow which were observed in the calibration of seven capillaries of varying diameter. It is shown that under certain experimental conditions deviations from Poiseuille flow are observed which may not be attributed to turbulence, and that this flow behavior may be described empirically by introducing the classical kinetic energy correction into the Poiseuille equation. INTRODUCTION Techniques have been developed for the measurement of the volume rate of flow of nitrogen through glass capillary tubes as a function both of the differential pressure applied and of the absolute gas pressure. Capillary tubes thus calibrated are frequently used to determine the rate of gas flow through a porous sample in the measurement of slip-corrected permeability. The purpose of this note is to describe the calibration procedure and to discuss some observed deviations from the ideal flow behavior predicted by the Poiseuille equation. EXPERIMENTAL PROCEDURE The volume flow rate of nitrogen as a function of the differential pressure was determined experimentally for a series of seven glass capillary tubes of varying diameter. As is shown in Table 1, the capillary radii in the series ranged from 0.004 cm for K1 to 0.07 cm for K7. The capillary tubes were cut from capillary tubing purchased on special order from several manufacturers and the bore radii were determined by microscopic measurement. The gas volume flow rate was measured for each capillary tube at a series of differential pressures in the range from 0 to 3 cm of mercury and at average absolute pressures of 1.0, 2.5, 4.0, and 6.0 atm. Experimental Procedure for Small Capillaries A schematic diagram of the apparatus used to calibrate the three smallest capillaries, Kl, K2, and K3, is shown in Fig. 1. By means of a standard Ruska Instrument Corp. volumetric pump (equipped with a synchronous motor drive, two stages of gear reduction, and a quick-change lathe gear box), nitrogen was displaced by mercury from a metal cell immersed in a constant-temperature bath. The pump, the line to the cell, and a part of the cell were filled with mercury. As mercury was forced into the cell, it displaced nitrogen which passed through the capillary tube being calibrated and into a large container with a volume of approximately 30 liters. Since the volume of this container was very large compared to the total volume change of the gas resulting from the action of the displacement pump, the absolute pressure of the system was essentially constant throughout any one run. Prior to any determination this pressure could be set at any desired level by means of an auxiliary nitrogen cylinder. The differential pressure across the capillary was measured with a Meriam Red Oil manometer and recorded together with the corresponding pump displacement rate which was equal to the gas flow rate. By repeating this process for a series of different displacement rates at each of the absolute pressures of interest, the data necessary for plotting the calibration curves for capillaries K1, K2, and K3 were obtained. All calibration measurements were made in a constant temperature room to minimize errors due to temperature fluctuations. In each run. the flow was maintained until equilibrium was established. Experimental Procedures for Large Capillaries The flow rates through Capillaries K4, K5, K6, and K7 required to obtain the pressure drops desired were larger than could be obtained from available constant displacement pumps, and it was thus necessary to employ an alternative calibration procedure. The arrangement of apparatus used in calibrating these capillaries at an average pressure of one atmosphere is shown in Fig. 2. Each capillary was calibrated by flowing nitrogen through the capillary and recording the differential pressure as a function of the flow rate. 'The differential pressure was measured with a Meriam Red Oil manometer and the flow rate was determined by collecting the effluent gas over water at constant pressure and recording the increase in volume per unit time after an equilibrium had been established. Appropriate corrections were made for the

Jan 1, 1953

By G. Carman Ridland

IN conjunction with a geological investigation of the silver-bearing veins at Contact Lake, Northwest Territories, Canada, a survey was made with a Geiger-Müller counter of the gamma-ray emissions from the rocks in the vicinity of the mine workings. Discontinuous pitchblende veins have been encountered occasionally in the silver-bearing fissures, and the geophysical survey was undertaken with the hope that abnormally high gamma-ray intensities, if detected, might lead to larger and more continuous pitchblende discoveries. Before the instrument was used at Contact Lake, preliminary tests were made, first with laboratory specimens at Princeton University, and later over known pitchblende deposits at the Eldorado property, LaBine Point, N.W.T. The Geiger-Müller counter, as adapted for field use, is described; the technique of transporting and operating the instrument is outlined; and the general precautions to be observed are discussed. The results obtained at Great Bear Lake show that the instrument is capable of detecting not only a pitchblende ore shoot in a shear zone, but also the mildly radioactive "host rock" at a considerable distance from the ore body. Hence, use of the Geiger-Müller counter is urged, not just for the detailed search for an ore body in a shear zone, but for the detection of possible radioactive "host rocks" in large-scale reconnaissance surveys of unexplored regions made by prospectors and members of federal geological survey parties.

Jan 1, 1943

By J. J. Gilman

Examination showed that characteristic cleavage step patterns are observed on the cleavage surfaces of undeformed, slipped, bent, twinned, compressed, and indented zinc crystals; and the effect of temperature is discussed. Dimples were seen to produce cleavage steps in a treelike pattern in otherwise undeformed crystals. The steps seem to originate when cracks intersect screw dislocations. IT has been known for a long time that the path of fracture in polycrystals may be discontinuous (see Jaffe, Reed, and Mannl for review). Recently, Kies, Sullivan, and Irwin2 have proposed, and given evidence, that crack propagation is discontinuous within individual crystals as well. Other evidence has been given by Low.' When discontinuous cracks within a crystal join together to make a macrocrack, the lamellae between each set of two cracks are torn somewhere, forming small cliffs. These cliffs appear as lines when the cleavage surface is observed microscopically.4,5 The lines have been called vein, tree, and riverlike markings by various authors, and they have sometimes been mistaken for fissures. The descriptive term cleavage steps is used in this paper. Cleavage steps vary in height over a wide range of values, from molecular dimensionsG to lor. and larger. Kies, Sullivan, and Irwin,2 as well as George,' have shown that the gross cleavage step patterns for plastics, polycrystalline metals, and for mono-crystals are sometimes similar. Thus, they depend mostly on the mechanical variables that prevail during cleavage and are relatively insensitive to the structure of the material. For example, parabolic markings2,7,8 sometimes result when cracks open up ahead of, and not coplanar with, the main crack front. If the advance crack has the same velocity as the main crack, their intersection line is a parabola, otherwise it is a hyperbola or an ellipse. The patterns are strongly affected by differences in crack velocities. This results in chevron patterns which point to the place of origin of the main crack. It is the purpose of this paper to demonstrate the existence of a mechanism of cleavage step formation which is a continuous rather than a discontinuous process. Also, certain characteristic step patterns are described, and the strong effect of temperature is shown. The specimens were zinc monocrystals (grown from 99.999+ pct pure metal). These were cleaved at room temperature and at — 196°C. Results and Discussion Cleavage step patterns are highly variable from point to point on a given specimen, as well as from one specimen to another. Although the patterns shown in the photographs are typical, they have been selected for graphic illustration. Figs. la and lb compare undeformed crystals that were cleaved at —196 °C and room temperature, respectively. Cleavage at room temperature (Fig. lb) resulted in a higher density of high steps (dark black lines) and enhanced the visibility of the fine background markings. Deformation by simple slip caused no marked change in the step patterns until the glide strain reached about 1.0. But, as Fig. lc shows, the density of high cleavage steps was greatly increased by large glide strains. Corrugations lying perpendicular to the slip direction may also be seen in Fig. lc. These are caused by deformation bands. The cleavage resistance of the crystal of Fig. lc was very high compared to undeformed crystals (estimated by the force on a needle required for cleavage). Striking and varied cleavage step patterns were observed on bent crystals. Two characteristic patterns that were observed on crystals bent at 25°C, and cleaved by reverse bending at —196°C, are shown in Figs. 2a and 2b. The first, Fig. 2a, consists of V-shaped lines similar to the parabolas of other materials2,7 Fig. 2b shows a pattern that is the equivalent of Fig. la, consisting of faint background lines with a few higher step markings. Cleavage of bent crystals at room temperature resulted in Figs. 2c and 2d. Now, the cleavage step lines show a strong tendency to follow one of two perpendicular paths. In Fig. 2c (bent once), many of the cleavage step components that lie parallel to the bend axis are assembled into irregular lines. In Fig. 2d (bent twice), the cleavage steps again tend to consist of two perpendicular components, but neither of the components is assembled into lines. Also, the step density is higher.

Jan 1, 1956

By L. R. Plitt, E. O. Lilge

Tests carried out with both kaolin and silica slurries show that flocculants of the polyacrylamide type can be used to improve the thickening performance of hydrocyclones. This thickening improvement demonstrates that contrary to previously held theories, flocs can be formed which are capable of resisting the shear forces in a hydrocyclone. For the 1.25-in.-diam cyclone used, optimum thickening occurs when the flocculant solution is injected into the slurry stream at or near the feed inlet. Hydrocyclones offer many distinct advantages over gravity thickeners. These advantages include simplicity, low initial and operating costs, small space requirements, and flexibility of operation. In spite of these advantages hydrocyclones have not been widely used as thickeners. The main reason for their lack of application is that hydrocyclones are unable to efficiently remove semicolloidal particles (less than 5 microns) from the suspending solution. In gravity thickeners, the fine particles can be induced to form particle aggregates, or flocs, which have the settling characteristics of large particles. In the hydrocyclone, however, it was always assumed that the existence of shear would prevent the formation of flocs.1-3 Thus, if no floc structure is retained, the thickening hydrocyclone must be designed so that its separation size is below the size of the smallest particle to be recovered. To obtain a very small separation size requires the formation of very high centrifugal forces, which necessitates the use of small-diameter cyclones. Small hydrocyclones have, in turn, very low throughput capacities which render them impractical for many industrial thickening applications. Thus, if the effects of flocculation cannot be utilized, the usefulness of hydrocyclones as thickeners remains limited to pulps which contain no very fine particles. It is well established that most substances acquire a surface electric charge when brought into contact with an aqueous medium. The repulsive interactions between similarly charged particles act to prevent flocculation. One method of flocculating a dispersion is to neutralize the repulsive surface charges by the addition of an electrolyte. The reduction of the electrostatic surface charge (Zeta potential) then permits the universal van der Waals attractive forces to operate between the atoms of the various particles and form particle aggregates. The lime additions used by thickener operators promotes flocculation by this mechanism. A second method of flocculating a dispersion is by the addition of long-chain macromolecules. In this case flocculation is brought about by a bridging mechanism in which the molecules are adsorbed with part of their length on two or more particles, thus forming a molecular bridge between the particles.4,5 The molecules also form bridges between themselves when a single particle is bonded to several polymer molecules. The type of bonding between the flocculant molecule and the particle may be hydrogen bonding, chemical bonding, or electrolytic attraction.6 The flour and glue which are used as thickener additives are believed to promote flocculation in this manner. In the past decade synthetic long-chain polymers with extremely high flocculating capabilities have been developed. The flocs formed by these new polymeric flocculants are larger and more shear-resistant than those formed by the presence of electrolytes.7 The advent of these flocculants raises the question: Are the flocs formed by these synthetic polymers stable enough to resist the liquid shearing forces in a hydrocyclone? The investigations reported in this paper were carried out in order to provide some answers to this question. EXPERIMENTAL WORK For the bulk of the test work a 5% slurry of commercially available kaolin with an average particle size of 5 microns was used. An initial evaluation of the available flocculants was carried out to determine which flocculant formed the most shear-resistant flocs. A combination of the techniques used by Healy7 and Booth8 was used for this purpose. This initial study revealed that the neutral high-molecular weight polyacrylamides produced the most shear-resistant flocs. One of these flocculants, Separan MGL*, was selected and then used for all the hydrocyclone tests. The flocculant was dissolved in water and added to the hydrocyclone as a dilute solution.

Jan 1, 1968

By Carl Wagner

AT elevated temperatures. most metals react with oxygen, sulphur, or halogen rather rapidly, although a coherent layer of the reaction product is formed and separates the two reactants from each other. The reaction proceeds, since one of the reactants or both dissolve and diffuse across the reaction product. In many cases the rate is diffusion-controlled as is indicated by the validity of the parabolic rate law of Tammann' and Pilling and Bed-worth. wott and Gurney' have suggested that diffusion processes also play an important part in the case of reduction reactions. This is confirmed by observations reported below. In general, however, the rate of reduction reactions is determined not exclusively by diffusion processes. Reduction of Silver Sulphide Above 179°C silver reacts with liquid sulphur very rapidly. Since the volume of silver sulphide is much greater than that of the equivalent amount of silver, a coherent layer of silver sulphide is formed in accordance with a rule established by Pilling and Bedworth.' According to Wagner','' silver ions and electrons migrate from the Ag-Ag,S interface across the silver sulphide layer to the Ag,S-S interface where the following chemical reaction takes place: 2 Ag +2 e + S Ag,S If silver sulphide is reduced by means of hydrogen, the equivalent volume of the reaction product, silver, is less than that of the initial substance. Accordingly, no coherent layer of silver is formed. Instead, fine filaments of silver grow from the silver sulphide surface into the ambient gas. This phenomenon has been investigated by many authors, especially by Kohlschiitter," who has also reviewed previous literature. Kohlschiitter has interpreted the observed phenomena by migration of "silver" dissolved in silver sulphide. According to Wagner,' silver ions and electrons are the migrating particles. The sequence of consecutive steps involved in the reduction of silver sulphide is shown in Fig. 1. Every- where at the silver sulphide surface, hydrogen reacts with sulphur so that excess silver ions and electrons are formed, which migrate at random until they are captured by a nucleus of metallic silver. If such a nucleus lies on the surface and material is furnished only from the base, the original nucleus is pushed outward and thus a filament grows. Removal of sulphur and formation of metallic silver may also take place at different points when silver sulphide is reduced by copper. The reaction is usually formulated as: AgL,S + 2 Cu = Cu.S + 2 Ag but the actual reaction products are silver and a solid solution of the two sulphides. Primarily, excess silver and electrons dissolved in silver sulphide are formed. After a certain degree of supersaturation has been reached, nuclei of metallic silver may form. If, however, a silver foil is in contact with the silver-sulphide phase, as is shown in Fig. 2, silver ions and electrons will migrate to the Ag,S-Ag interface where they are captured. To confirm this scheme, a composite sample, with the geometry shown in Fig. 2, was made by pressing silver sulphide tablets 0.6 cm in diam and 0.4 cm high together with a copper cylinder and a silver foil in crucibles of iron, which does not react appreciably with silver sulphide at 400°C. After heating for 3 to 7 hr at 400°C. the specimens were cut normal to the phase boundaries. It was found that the thickness of the silver foil had increased from 0.01 cm as initial value to a maximum value of 0.06 cm. In the interior of the silver sulphide tablets only traces of metallic silver were observed. These observations show clearly that silver ions and electrons may migrate over distances of several millimeters before they form metallic silver. Reduction of Cuprous Sulphide by Iron The behavior of cuprous sulphide is very similar to that of silver sulphide, since the lattices of the high temperature modifications are identical, but in Cu.S there is a variable deficit rather than an excess of metal. To investigate the displacement of copper by iron, cuprous sulphide powder covered by a copper foil was pressed in iron crucibles and heated up to 800 °C for 3 to 7 hr. The thickness of the copper foil increased from an initial value of 0.005 cm to a nlaximum value of 0.029 cm. In the interior of the

Jan 1, 1953

By N. E. Rogen, N. J. Grant

WHILE direct measurements of the growth of precipitate particles during aging is of fundamental value, few such measurements have been made. Direct measurements by means of optical or electron-microscopy and X-ray techniques are preferred, however, many of the aging studies have been based on indirect methods such as electrical resistivity and hardness. Because of the minute size of most precipitate particles (less than 1000A) the light microscope is of limited use while electron microscopy is subject to slowness, etching problems and consequent resolution problems. It is fortunate that alloys of the Nimonic type, based on Ni-Cr-Ti-Al, lend themselves to accurate and relatively easy particle size measurements. With proper balance of titanium and aluminum, the only aging precipitate is the gamma prime (r') Ni3,(Al, Ti)2 phase and this phase is the basis of the high-temperature strength of these allos.3-6 The Ni3(Al, Ti) phase is a face-centered-cubic, ordered structure with nickel atoms occupying the cube faces. Titanium atoms can replace three out of every five aluminum atoms and when substituting do so preferentially.2 Electron microscopy has shown that during aging of most of the commercial alloys of this type, precipitate particles are unusually uniform in size and distribution, and that the volume of (r') phase is large (20 pct).4,7 The aim of this investigation was to measure the growth of (y') phase during aging. In so doing, it was hoped that a clearer understanding of the aging process would be attained. X-ray line broadening was used as the measure of precipitate particle size. This technique was selected because it can measure and average the diameter of thousands of particles in one operation. The variations in hardness and matrix lattice parameter with aging were also studied and related to the particle size. EXPERIMENTAL PROCEDURE An alloy of the following composition was studied: Cr Ti A1 C Ni Wt pct 20.71 2.98 1.43 0.04 bal. At. pct 22.06 3.47 2.95 0.18 bal. The alloy, a 15- lb vacuum melt, was forged to 1/2-in. diam at a temperature of 1900" to 2200°F; was solution heat treated for 4 hr at 2000°F and water quenched; and was then aged in various ways. The ASTM grain size was 4 to 5. No (7') phase could be detected by X-ray analysis after solution treatment and electrolytic extraction. Aging was performed on 2-in. long specimens at 1400°, 1500°, and 1600°F for increasing times. One-half inch sections were removed after each time increment and were then electropolished in a solution of H3P04 saturated with chromium trioxide at a potential of 30 v and rectified with a tantalum electrode. Rockwell hardness measurements were taken using one side of the polished specimen. Matrix lattice parameter determinations were made on the other side using filtered chromium radiation references with the position of the (220) line of a silicon standard. To enable the precipitate particles of the (y') phase to be measured using X-ray line broadening techniques, it is first necessary to separate and concentrate this phase by electrolytic extraction. Extraction is necessary because the difference between matrix and precipitate lattice parameters is only approximately 0.5 pct and intensities of.the (y') phase lines are very weak relative to those of the matrix. The extraction techniques employed have been described before and found to produce a reasonably quantitative separation.398 A water solution of 15 pct H3Po4 is used at a current density of 0.5 amp per sq in. at 6 v. The precipitate particles are separated from the liquor by centrifuging and decanting and are then washed, dried and repowdered. A plot of the X-ray intensity vs diffraction angle for the (111) line of the precipitate particles was used as a measure of particle size. The intensity curve approximated the shape of Gaussian distribution function and its breadth was measured at the half height. The (220) line of a silicon standard was used to correct the measured line breadth for instrumental and other broadening errors. The Scherrer formula was used to calculate particle

Jan 1, 1961

By P. T. Chiang

Chemical etching methods for the simultaneous revealing of the tellurium or selenium Phase and the chalcogenide grain boundaries of the alloy systems are given. A tellurium eutectic was found Present in zone-melted ingots. Similarly, a selenium monotectic was present in ingots. In general, the second phase (tellurium or seleniumn) occubies three different sites; viz., along the chalcogenide grain boundaries, as inclusions within the chalcogenide grain, and on the undersurface of the ingot. The detection limit for the tellurium phase is about 1 u in width. THERMOELECTRIC materials based on Group V (bismuth, antimony) and Group VI (selenium, tellurium) elements have aroused considerable interest in recent years in the practical application of thermoelectric cooling. In many cases, a small amount of excess tellurium (or selenium) was added to the material to optimize its thermoelectric properties. Then the question immediately arises as to the number of phases present in the resultant alloy. In the binary systems of Bi-Te, Sb-Te, and Bi-Se, the congruent melting compositions have been reported to be non-stoichiometric and are represented by Bi~Te respectively. It is to beexpected and known that Bi2Te3 and SbzTe3 crystallize from the melt with an excess of bismuth and antimony in the lattice and that tellurium forms a eutectic.~' The same could be assumed to take place in the pseudo binary systems of (Bi,Sb)zTe3 and Bi2(Se,Te)3 as well as in the system studiedby puotinen5 and other workers. Likewise, BiaSe3 crystallizes from the melt with an excess of bismuth in the lattice and selenium forms a monotectic.~ Therefore, in practice, alloys solidified from the melt often contain a second phase (tellurium or selenium) in one region or another of the solid mass even without the addition of excess tellurium (or selenium). ~u~~recht' studied the thermoelectric properties of (Bi,Sb)2Te3 alloys with excess tellurium and simultaneous additions of selenium. He mentioned that the materials show two phases because of the considerable excess of tellurium or selenium. However, he did not report as to how the tellurium or selenium phase was identified. It is generally believed that the presence of an excessive amount of tellurium or selenium phase in the alloy would adversely affect its thermoelectric properties and its uniformity. Consequently, there is a need for a simple method for the identification of the tellurium and selenium phase. The quantity of the second phase present is usually too small to be detected either by chemical analysis or by normal X-ray techniques. This investigation was therefore carried out, first, to devise a simple metallographic method for the identification of the tellurium or selenium phase coexisting with the chalcogenides and, second, to determine the distribution and specific location of the tellurium or selenium phase in the ingots. EXPERIMENTAL PROCEDURE The starting materials used for the alloy preparations were 99.999 pct pure bismuth, antimony, and tellurium and 99.997 pct pure selenium. The bismuth and antimony were obtained from Consolidated Mining and Smelting Co. of Canada Ltd., while the selenium and tellurium were obtained from Canadian Copper Refiners Ltd. The tellurium was purified further in the laboratory by zone refining. The elements were pulverized in a stainless-steel pestle and mortar. The amounts for the desired composition were weighed out each time on an analytical balance to make up a 100-g sample. Then the sample was introduced into a Vycor ampule (19 by 150 mm), pumped down to a vacuum of 10"5 Torr for 15 min, and sealed off. The ampule was then heated in a horizontal resistance furnace at 800" to 900°C for about 20 hr. During this period the assembly was rocked back and forth several times to ensure good mixing. At the end of the heating period, the ampule was quenched in cold water and then transferred to the zone-melting apparatus described in a previous publications to grow large-size aligned polycrystals. The background and ring-heater temperatures were adjusted to make the freezing solid-liquid interface slightly convex to the liquid. The recorded temperature gradient in the vicinity of the freezing solid-liquid interface was around 15°C per cm. The ampule was moved horizontally at a speed varying from 0.4 to 2 cm per hr so that the ring heater would cover the whole ingot length from end to end. A single zone-melting pass was used for the Bi-Te, Sb-Te, and Bi-Sb-Te ingots. Two passes in the forward and reverse directions were carried out for the Bi-Se and Bi-Se-Te ingots. Six passes in the forward and reverse directions were performed for the Bi-Sb-Se-Te ingot. The zone-melted ingots were found to contain several large crystals, with their basal planes (0001) approximately parallel to the growth axis. Samples of bismuth and antimony tellurides coated with a layer of tellurium, and bismuth selenide coated with a layer of selenium, were prepared for comparison in phase identification. These coatings were made by dropping a piece of the zone-melted ingot into some molten tellurium or selenium under argon atmosphere and allowing them to cool slowly to room temperature. The metallographic specimens were prepared by

Jan 1, 1969

By J. R. Long, T. R. Graham, C. W. Matthews, R. S. Dean

IN a previous paper§ the authors reported on the mechanical properties of a 65 per cent copper, 10 per cent manganese, 25 per cent zinc alloy as compared with similarly processed cartridge brass. Additional investigations by these laboratories, on higher copper alloys, have demonstrated that at lower zinc concentrations even larger amounts of pure manganese may be added to copper-zinc alloys without exceeding the single-phase solid solution limits, and that similar increases in tensile strength, yield strength, and hardness may be obtained without excessive decreases in ductility. Several compositions in this range showed also a decided color change with increasing manganese. The normal "brassy" color was considerably lightened and reduced to a faint yellow cast at 15 per cent manganese. With higher manganese contents the alloys were essentially white and similar in appearance to the nickel-silver alloys. From this work it appeared that it would be desirable to determine more completely the properties of the wrought and annealed white alloys. Accordingly, a more detailed study was planned of an alloy having the composition 70 per cent copper, 20 per cent manganese, and 10 per cent zinc. This alloy remained single-phase throughout the working and annealing cycles of the preliminary tests and appeared to be about the strongest of the white single-phase alloys. The project included also an investigation of additional alloys, deviating from this composition by 5 per cent of each of the three components to evaluate the effects of variation in composition; also a study of the properties of the central alloy made with silicothermic manganese. MATERIAL PREPARATION Electrolytic manganese, wirebar copper, and electrolytic zinc were used for the preparation of the alloys. Representative analysis of the electrolytic manganese seldom exceeds 0.01 per cent iron, 0.02 per cent sulphur and 0.02 per cent lead, with no silicon or aluminum. A typical sample of the silicothermic manganese metal contained 2 per cent iron, 0.81 per cent silicon, 0.i6 per cent carbon, and 0.36 per cent aluminum. Melting and alloying were performed in a high-frequency furnace with magnesia crucibles. Melts were deoxidized with small aluminum additions and cast into 25-lb. slab ingots. Care was exercised in deoxidation to avoid excessive amounts of residual aluminum, which has been found to have significant effects on alloys in this system. All ingots were hot-rolled at 1200° to 1300°F. and then cold-rolled with intermediate anneal-

Jan 1, 1945

Dimitri Konstantinovitch Tschernoff, was horn in Petrograd, Russia, on Nov. 1, 1839, and died in Yalta (Crimea) in the south of Russia, on Jan. 2, 1921. He obtained his early education in the Russian Gymnasium, corresponding to the American high school, and in the Technologic Institute. On graduation from this Institute in 1858, he was engaged as a professor of geometry and algebra and later became a librarian and superintendent of the museum in the same Institute. He also attended lectures in the mathematical physics section at the Univrrsity of Petrograd from 1859 to 1862. In 1866, Professor Tschernoff left the Technologic Institute and entered the employ of the Obouchoff steel plant, founded in 1863 for the manufacture of guns. Here he did his most important work on the heat treatment of steel, its crystallization and metallography. In 1880, he left the Obouchoff plant and went to the south of European Russia, where he discovered and developed some rock-salt mines. This enterprise brought him a rather large fortune. In 1884, he returned to Petrograd and during the next four years held several prominent positions in government departments. In 1899, he became professor of metallurgy in the Michael Artillery Academy, and retained that position until the time of the Russian Revolution. In 1902, Professor Tschernoff was elected an honorary member of the American Institute of Mining and Metallurgical Engineers. In September, 1917, Professor Tschernoff was sponding his vacation, as usual, in the city of Yalta (Crimea) in the south of Russia, with his wife and one of his daughters. The revolution progressed so rapidly that they were unable to return to Petrograd, and were compelled to stay in Yalta without provision for the winter season. Suffering from hunger. and lack of sufficient clothing, and deprived of his books, Tschernoff nevertheless continued his studies and gave a number of lectures on steel at the Polytechnic Institute. At the same time he worked hard on some. mathematical problems. His health broke down through long-continued under-nourishment. His works in the metallurgical field are well known to the students of metallurgy; good abstracts of his most important papers were published in Revue de Metallurgie (1915, pp. 829-882) in commemoration of his 75th birthday.

Jan 1, 1922

Dimitri Konstantinovitch Tschernoff, was horn in Petrograd, Russia, on Nov. 1, 1839, and died in Yalta (Crimea) in the south of Russia, on Jan. 2, 1921. He obtained his early education in the Russian Gymnasium, corresponding to the American high school, and in the Technologic Institute. On graduation from this Institute in 1858, he was engaged as a professor of geometry and algebra and later became a librarian and superintendent of the museum in the same Institute. He also attended lectures in the mathematical physics section at the Univrrsity of Petrograd from 1859 to 1862. In 1866, Professor Tschernoff left the Technologic Institute and entered the employ of the Obouchoff steel plant, founded in 1863 for the manufacture of guns. Here he did his most important work on the heat treatment of steel, its crystallization and metallography. In 1880, he left the Obouchoff plant and went to the south of European Russia, where he discovered and developed some rock-salt mines. This enterprise brought him a rather large fortune. In 1884, he returned to Petrograd and during the next four years held several prominent positions in government departments. In 1899, he became professor of metallurgy in the Michael Artillery Academy, and retained that position until the time of the Russian Revolution. In 1902, Professor Tschernoff was elected an honorary member of the American Institute of Mining and Metallurgical Engineers. In September, 1917, Professor Tschernoff was sponding his vacation, as usual, in the city of Yalta (Crimea) in the south of Russia, with his wife and one of his daughters. The revolution progressed so rapidly that they were unable to return to Petrograd, and were compelled to stay in Yalta without provision for the winter season. Suffering from hunger. and lack of sufficient clothing, and deprived of his books, Tschernoff nevertheless continued his studies and gave a number of lectures on steel at the Polytechnic Institute. At the same time he worked hard on some. mathematical problems. His health broke down through long-continued under-nourishment. His works in the metallurgical field are well known to the students of metallurgy; good abstracts of his most important papers were published in Revue de Metallurgie (1915, pp. 829-882) in commemoration of his 75th birthday.

Jan 1, 1922

HeRbert A. MeGRaw, San Luis de la Paz, Guanajuato, Mex. (communication to the Secretary*) :—Although Mr. Bordeaux prefaces his paper with the statement-that it is a general outline of practice in the Republic, many of his statements seem to be made from the view-point of a particular case, which does not always agree with general practice. For the purpose of calling attention to some of these variations, I respectfully offer the following comments: The operation of crushing and grinding is performed by so many different methods and systems that it is useless to select any one as the standard. However, primary crushing in rock-breakers followed by stamps is thus far so general that it might be so classified. Whether or not it is the best way, is open to question. Regrinding may be performed by any of the various types of Chilean mills, Huntington mills, or similar machines, or the material may be taken directly from the stamps and delivered to the tube-mills. Mr. Bordeaux's statement that " the slimes can be treated only by decantation; the new Butters slime-filter, as used in Nevada, does not seem to be successful with silver-ores," is surely an error. All over Mexico many of the purely silver-ores are being successfully handled by the Butters or similar filters, such as the Moore and the Burt filters, and a letter to the manufacturers of these filters will undoubtedly bring a list of the silver-ores now being successfully treated in this way. The statement that crushing silver-ores in solution is impossible is equally erroneous. Most modern mills crush the ore in solution, in some cases containing as much as 0.12 per cent, of KCN. I cannot for the moment recall any modern mill in Mexico which does not follow this practice. There may be some reason for it in particular instances, but, generally speaking, the practice is to crush in solution. Care in installation avoids any mechanical loss of cyanide, and the chemical loss is so small as to be negligible.

Jan 1, 1910

By John E. Willson, Ben L. Seegmiller

A portable electronic instrument was designed and constructed to detect unknown stress magnitudes in rocks. The principle used to detect stress is based on the propagation velocity method. This method allows the stress in a rock subjected to a load of unknown magnitude to be determined, provided that the wave velocity-stress relationship for similar rock is known. This is accomplished by measuring the travel time of longitudinal mechanical waves passing between two points a set distance apart in a rock. The velocity of the wave is calculated and the stress determined from the wave velocity-stress relationship. If the sending and receiving transducer spacing is constant, a time vs. stress relationship rather than the velocity-stress relationship may be used. The method is nondestructive and tests can be made without drilling or otherwise disturbing the rocks. The first studies undertaken in the United States to determine stress in rocks using propagation velocity techniques were reported by Obert1,2 in 1939 and 1940. The Soviet Union first reported using propagation methods to study rock pressures in 1951.8 Success of the method led to the development of a pulse-type ultrasonic seismoscope4 in 1953. Using this instrument, Ivanov and Betaneli5,6 in 1963 succeeded in devising and testing under field conditions a method of investigating coal pillar stresses. In 1967 Osipova7 reported results of similar studies in the Nakhichevan salt mines. In France, Tincelin8 has used the propagation velocity method to study the stress distribution in iron ore pillars. Uhlmann9 has investigated stresses in salt and potash pillars in Germany, using velocity techniques. Determination of uniaxial stress by propagation velocity methods is limited to rocks which have readily detectable wave velocity-stress variations. The present stress detection instrument is restricted in application to rocks which have a velocity change under stress of at least 300 fps. Examples of rocks which meet this requirement are sandstones, coal, and possibly some limestones. Testing of this instrument was limited to a laboratory study and the results may or may not be indicative of what would be found in a field test. A program of field experiments to study the feasibility of using this instrument to determine mine pillar and tunnel stresses is in progress. Instrument Design The instrument has two main components: A probe and a control-display unit. The probe is a hand-held device to which two identical rodlike transducers are rigidly mounted. Coaxial cable connects the probe to the control-display unit which is mounted in an enclosed carrying case measuring 7 % x 9 x 13 in. The instrument is designed so it may be carried and operated by one man. Weight of the probe and enclosed control-display unit is approximately 20.1b. The probe consists of two transducers identical in construction. One transducer is used to convert electronic pulses to mechanical waves and transmit these waves into a rock. The other detects the transmitted waves in the rock and converts them back into electronic signals. The basic element in both transducers is a piezoelectric crystal. The crystal is a disk made of lead titanate zirconate and has a natural resonant frequency of 400 kHz ±1% in the thickness mode. A schematic of one of the two identical transducing elements is shown in [Fig. 1.] A spacing of 6 in. between sending and receiving transducers has been found to be most satisfactory. The control-display unit consists of a pulse generator and a 1-in. oscilloscope. Various electronic devices are used for the power supply, amplification, and calibration. The amplitude of the square wave from the pulse generator can be continuously varied between 0 and +20 vdc. Pulse width can be set at 1, 2, 3, or 4 µsec. The repetition rate of the pulse can have the following values: 50, 75, 100, 150, 200, 250, 300, 400, 500, 750, and 1000 Hz. The oscilloscope delay system allows the travel time of the longitudinal wave passing through a rock to be measured to an accuracy ±0.1 µsec in the range from 0 to 995 µsec. Fig. 2 is a schematic of the various electronic sections in the control-display unit. Laboratory Testing The first step in using the instrument is to develop a velocity-stress or a time-stress curve for the par-

Jan 1, 1972

Jan 1, 1969

Jan 1, 1917

By P. R. Celmer, Leonard R. Weisberg

THE principle of fractional crystallization has been successfully used to prepare high-purity (99.999 pct) Ga. Hoffman and Scribnerl removed single crystals of gallium solidifying in a gallium melt, while Zimmerman2 grew single crystals from the melt by the Kyropolous technique. In contrast, attempts at purifying gallium by zone refining have been less successful. ichards, reported that despite the passage of 40 zones through a gallium ingot, there still remained 5 to 70 ppm each of Cu, Fe, Ca, Mg, Si, Al, and Ag. Previously, Detwiler and Fox4 detected only one impurity, Pb, segregating in zone-refined ingots. These surprising results prompted an investigation of the factors controlling impurity segregation in gallium. Possible reasons for this were insufficient diffusion of impurities in the melt; recontamination of the melt by its oxide film which is not affected by the passage of the zone; reaction of gallium with the boat; sudden freezing of gallium following supercooling, especially since gallium easily supercools to and trapping of impurities at grain boundaries. Impurity segregation tests were carried out by directionally freezing gallium using the Bridgman rnethd, modified in that the molten gallium is lowered out of a furnace into a slush of dry ice and trichloroethylene, thus minimizing supercooling. Since the gallium is contained vertically, the oxide film is in contact only with the tail end of the melt. It was found that Teflon makes an excellent crucible for gallium since it is quite pure, non-reactive, translucent, flexible, machinable, and is not wet by gallium. The gallium crystals could be grown at various speeds, and the melt could be vigorously stirred by a Teflon rod moving through the gallium in a vertical reciprocating fashion. Single crystals could be grown by placing a solid Teflon plug at the bottom of the melt drilled out in such a way to cause the solidifying gallium to follow a winding path. Thus, even if many crystals are originally nucleated, only one grain will predominate. The grain structure of the gallium crystals was revealed by an etchant composed of equal volumes of HC1, HNO3 and HF, diluted with water to half strength. Emission spectrographic analyses were carried out on samples removed from the front and tail ends of the resulting gallium ingots. Typical results of this study are summarized in Table I. The rate of freezing in all three cases was about 1 in. per hr. It can be seen that even though stirring of the melt does help, it is even more important to grow a single crystal of Ga in order to obtain good segregation of impurities. The effect of crys-tallinity on the segregation of impurities was previously observed6 in the directional freezing of germanium; however, in this case, the effect was much less pronounced. This dependence of impurity segregation on the crystalline perfection of Ga may be related to its thermal conductivity which is the most anisotropic of all metals.7 The anisotropic thermal conductivity can cause the solid-liquid interface to be nonuniform, thus leading to trapping of impurities during freeing, and therefore reduced segregation. In conclusion, it is indicated that zone refining of gallium would be more successful if seeding and similar precautions are taken to insure single crystal growth. The authors are indebted to Mr. H. H. Whitaker for the spectrographic analyses and to Drs. B. Abeles and F. D. Rosi for helpful advice and encouragement throughout the course of this work. This research was supported by the Electronics Research Directorate, Air Research and Development Command, under Contract No. AF33(616)-5029. REFERENCES 'J. 1. IToffmon and B. T. Scribrer: I. Research h'atl. Bur. Standards, 1935, "01. 15, p. 205. 'W. Zirnmerman: Science, 1954, vol. 119, p. 41. %J. L. Richards: Nature, 1956, vol. 117, p. 182. 'D. P. Detwiler and W. M. Fox: I. Metals, 1955, "01. 7, p. 205. 5P. W. Bridgman, Proc. Am. ilcod. Sci., 1925, vul. 60, pp. 305,385,423. "S. L1. Christian: private c ommuni cation. 'K. W. Powell: roy. Sac., 1951, vol. 209, p. 525. 'W. G. Pfann: Zone Re fining, p. 20. John Wiley and Sons, Inc., New York, L058.

Jan 1, 1962