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By Cornelius J. Dwyer

It is possible to hold a very optimistic view of the future of the U.S. coal industry, and there are those in the coal industry who generally choose to do so. For example, a major coal company stated recently in its annual report, "Coal's prospects appear brighter today than at any period in the past." In order to continue in this state of euphoria, it is only necessary to remind oneself of the following "facts":

Jan 7, 1967

By C. E. Tsoutrelis

A new method for determining rock drillability in diamond drilling is discussed; the method takes into consideration both penetration rate and bit wear. The method is based on drilling a rock specimen under controlled laboratory conditions using a model bit. The technique used for determining the experimental variables is extremely simple, quick, and reliable. Drillability is then determined by the mathematics of drilling. In considering the different factors that affect diamond drilling performance, the nature of the rock to be drilled is of outmost importance since it affects significantly the drilling costs and such other variables as bit type and design, drilling thrust, and bit rotary speed. Many attempts have been made to study this effect by correlating actual drilling performances either to certain physical properties of the rock being drilled1-? or to test drilling data obtained under laboratory conditions.7-13 These attempts were aimed at providing a reliable method of predicting by simple means the expected rock behavior in actual drilling, thus giving the engineer a tool to use in estimating drilling performances and costs in different types of rock. The purpose of this paper is to describe such a method by which rock drillability (a term used in the technical literature to describe rock behavior in drilling) could be determined in diamond drilling. It is believed that the proposed simple and reliable method will cover the need of the mining industry for a workable method of measuring the drillability of rocks. It should be emphasized, however, that since drill-ability depends on the physical properties of rock and each drilling process (diamond, percussive, rotary) is affected by different or partly different rock properties,14-l6 the proposed method of determining rock drillability cannot be extended to the other drilling processes. The results presented in this paper form part of an extensive three-year research program carried out by the author in the laboratories of the Greek Institute of Geology and Subsurface Research. During this period the effects of the physical properties of rocks and of such operational variables as drilling thrust and bit rotary speed in diamond drilling were investigated in detail. DRILLABILITY CONCEPT The literature is not devoid of drillability studies. While there are a number of investigators1,3,5-7,9-0,12-13,17 who have attempted to establish by direct methods (i.e., drilling tests under laboratory conditions) or indirect (i.e., through a physical property of rock) an index from which the drilling performance in a given rock may be estimated, very few6-7,9,12, of the proposed methods seem to be of much practical value to the diamond drilling engineer and none to date has been universally accepted. Commenting on the proposed methods for assessing rock drillability, Fish14 remarks that "for a measure of drillability to be accepted it is essential that penetration rate at a given thrust and bit life are elucidated as otherwise the method is of little value." This statement should be examined in more detail by making use of the penetration rate-drilling time diagram obtained in drilling a rock under constant operational conditions. Furthermore, the merits of using this diagram to describe rock drillability will be pointed out. At the same time reference will be made to this diagram when discussing some previously proposed methods. Fig. 1 illustrates such a diagram for three rocks,A, B, and C, which have been diamond drilled under identical conditions. It is assumed here that rocks A and B have the same initial penetration rate, i.e., VOA = Vog, but since rock B is more abrasive than A, rapid bit wear occurs and as a result the fall of its penetration rate with respect to time is more vigorous than in rock A. This is shown graphically by a steeper V = f(t) (0 curve in this rock than in rock A. Rock C has a lower initial penetration rate, due to higher strength properties16 but since it is not very abrasive, only a slight fall of its penetration rate occurs during drilling (in this category are some limestone and marbles with compressive strength above 1000 kg per sq cm). It follows from the foregoing considerations that the characteristic for each rock curve (I) is a function of (i), the penetration rate of the rock Vo recorded at the instant of commencing drilling, which determines the starting point of the curve (1) on the y-axis and (ii), the abrasive rock properties which determine the rate of fall of Vo with respect to time. Thus, curve (I) provides an actual picture of the rock behavior in drilling for given operational conditions, and it can be used with complete satisfaction to assess rock drillability. It can be seen clearly from Fig. I that proposed methods for assessing rock drillability by measuring the

Jan 1, 1970

By Joseph Jensen

No outstanding example of an important producing unit operation exists in California today where the competitive drilling drainage feature is or was entirely eliminated We need not feel, however, that the thought of unit operation had its birth in 1924, when Henry L. Doherty named and sponsored it so strongly before the American Petroleum Institute and our own organization. No man or company in California ever drilled a wildcat well without exerting every possible effort to get all of the structure, so as to control drilling and avoid competition. Overproduction did not begin in 1923, so there has always been the wish to avoid it. In this state the practice of selling acreage around a wildcat has not been followed, except possibly in rare instances. The operator drilling the wildcat knew he must pay the bill alone, so he endeavored to get the benefit of his effort by tying up all of the land around his well and by so planning his different lease obligations as to avoid as much offsetting as possible. If he failed to get all of the land, it was because someone's price was too high, some other oil man also had the same idea and already held some lands, a competitor took leases away from him while his work was still incomplete, or (as was so often the case) the hidden structure when developed did not prove to be where the wildcatter thought it would be. The last named condition often led to a forced drilling campaign by the last leases secured and thus to serious drilling drainage problems. Ownership of the Land The land situation differs a great deal in various parts of the state. In the San Joaquin Valley, all the land is surveyed into sections and townships. Railroad land grants embraced a part of the land. In the areas that were developed at an early date, as at Kern River, Coalinga, McKittrick and the Sunset-Midway field, such land as the railroad company's diligent land department had been unable to sell for a song as grazing land still remained in its ownership. Operation and ownership

Jan 1, 1930

By E. J. Duggan

THE mine and mill of the Climax Molybdenum Co. are at Climax, Colorado. Climax is on Fremont pass directly on the Continental Divide, at an elevation of 11,400 feet. DESCRIPTION OF ORE The Climax ore-bearing rock is essentially an altered and highly silicified granite, fully half of the gangue being quartz. Molybdenite is the only mineral of economic consequence and most of it is intimately associated with quartz in the form of fine veinlets and stringers. Other minerals are molybdite, pyrite, and chalcopyrite. While the molybdite may be readily extracted by hydrometallurgical methods, its content is too low to make such operations profitable. The pyrite content ranges from 2 to 5 per cent and that of the chalcopyrite from 0.03 to 0.05 per cent. There is not enough copper to make its recovery attractive and one of the metallurgical problems is the elimination of it and the pyrite from the product. On account of the close association of the molybdenite with the quartz and the necessity of eliminating the pyrite and chalcopyrite from the final product, fine grinding followed by flotation is the only feasible method of concentration. HISTORY Construction of the first milling unit was started in 1017 and it was operated during parts of 1918 and 1910. In the postwar years, there was almost no demand for the product and production was at a standstill until 1024. The Company's research campaign to develop the use of the metal began to show results in that year. From 1926 to 1932 production ranged from 500 to 1200 tons per day. In 1931 an additional mill section was built and production was gradually increased until in 1934 and 1935 about 3000 to 4000 tons was milled per day. This tonnage overtaxed the milling facilities, and as the demand for molybdenum was growing constantly, additional milling equipment was needed. In 1936 and 1937 another crushing plant, six additional mill sections and the necessary auxiliary plants were constructed and brought into operation. This plant was designed to mill I0,000 tons per day, but it was not long before 12,500 tons was being treated during periods of peak demands. During the summer of 1941, to meet defense needs, the mill has been required to treat 15,500 tons per day. This has been accomplished with little plant expansion and at no loss in recovery, as will be described later. To increase capacity still further, one more primary section is now being built. This will bring capacity to 18,000 tons per day, which can be stretched to 20,000 tons at a small sacrifice in recovery. CRUSHING There are two crushing plants: No. I, of 5000 tons capacity (flowsheet in Fig. I) and No. 2, of 15,000 tons capacity (Fig. 2).

Jan 1, 1942

By A. T. English

X-ray dif action techniques were used to investigate ordering and domain coalescence for the B2 (CsC1) superlattice in this alloy. Essentially complete disorder is obtainable by drastic quenching. isothertmal ordering occurs very rapidly at temperatures between 565° and 680°C, only a few seconds being required for development of substantial long-range order. A very fine antiphase dormain structure, found in samples annealed for short times, undergoes coalescence with further annealing. Domain "size" is found proportional to (t)1/2 . This Yate law can be derived by adapting the formalism of Hillert's analysis 01- metallurgical grain growth. For this Purpose the material is descvibed in terms of a "Swiss-cheese " structure, consisting of two multiply connected, mutually intertwined domain volumes. The observed activation enevgy for coalescence, 70 kcal per g-atom, agrees with an estit~lated value ,for volume diffusion in disordered rrzaterial. It is suggesled that the experimental value vejlects the substantially disordered environment of mobile vacancies located in the moving antiphase domain boundary. The alloy Fe-Co-2V is bcc below about 900'C and orders into a B2 (CsC1) superlattice below about 730c It has important applications in magnetic components, including many requiring extensive cold rolling.* example, Marcinkowski and Brown6 observed a re1atively small as-quenched domain size of about 250Å in B2 Fe3A1. Since there appear to be no published data on domain coalescence in B2 alloys, this process was studied in detail. MATERIALS AND EXPERIMENTAL TECHNIQUES A commercial high-purity alloy, nominally 49 Fe-49Co-2V, was obtained from the Arnold Engineering Co. in the form of cold-rolled sheet 0.004 in. thick. Samples were annealed for 1 hr at 800°C in dry H2 to produce disorder and quenched into iced brine. They were then annealed in a nitrate-nitrite salt bath for various times at temperatures between 525° and 625°C. Estimates of the LRO parameter S and the APD size D were made using established X-ray diffraction techniques. Superlattice peaks are best observed using CoKa radiation, for which the value of (fFe-fCo) is maximized. Peak-to-background intensity ratio was improved by filtering CoKß from the incident beam to eliminate sample fluorescence, and by using a pulse-height analyzer. The LRO parameter S was computed from the ratio of integrated intensities I 100/I 200- Owing presumably to systematic errors associated with the presence of crystallographic texture and X-ray extinction, only rough agreement was obtained between experimental and theoretical (absolute) intensity ratios. For this reason certain experimental refinements (e.g., use of balanced filters) were considered superfluous and were omitted. Emphasis was placed on maximizing intensity in order to reduce the time taken to accurately determine the contour of the very small (loo), peak. This was done by point counting 105 counts at appropriate intervals. Background intensity averaged about 1200 cps.

Jan 1, 1967

By R. H. Raring, F. E. Martin

A high speed gas quenching dilatometer useful in studying phase transformations in low alloy steels is described. Changes in specimen length are measured by means of an electrical micrometer tube. The maximum instantaneous cooling rate is approximately 5000°F per sec; the maximum average cooling rate from 1650' to 950°F is approximately 2900°F per sec. Data for steels of 0.11 pct and 0.67 pct C content are included. KNOWLEDGE of phase transformations as they occur in an alloy under conditions of continuous cooling affords valuable insight into its properties. The transformation characteristics during continuous cooling of steels of high hardenability, which decompose entirely to martensite at fairly slow cool-

Jan 1, 1957

By Arthur R. Kommel, Robert F. Mehl, Gerhard Derge

The orientation relationships resulting from allotropic transformations and the formation of segregate structures in metals and alloys have been the subject of the eight earlier papers in this series'. A brief summary of orientation studies has also been given by Sachs2. A survey of these papers discloses that the factors that determine the orientation relationship of a precipitated phase to its parent solid solution, as well as the outward form and appearance of the new phase, are not completely understood. It is now evident that crystallographically analogous systems, as a rule, exhibit the same type of Widmanstatten figure and orientation relations, so that useful information is not to be expected from examination of a new alloy involving lattice combinations of which the orientation relationships are already known. Therefore, the determination of the relations existing between lattice types that have not already been studied seems to be the most promising mode of attack upon the problem; both of the systems reported in this paper represent new combinations of lattice types. A. The Mg-Mg2Sn System The magnesium-tin equilibrium diagram given by Hansen3 shows the phase Mg2Sn to be the only intermediate phase. The solid solubility of Sn in Mg decreases from 14.8 weight per cent at the eutectic temperature, 561' C., to 2.3 per cent at 450°, while no solid solubility of Mg in Mg2Sn has been observed. The crystal structur: of Mg is close-packed hexagonal with a0 = 3.202 A. and co = 5.199 A.4, while Mg2Sn is of the CaF2 type with a. = 6.78 A., with four molecules in a unit ce115,6. Alloys from two different sources have been used: (1) those supplied by the Dow Chemical Co., which contain 6 and 8 weight per cent Sn, and (2) those prepared in this laboratory, containing 8 and 13.5 per cent Sn. The latter were made from Dow high-purity Mg and Baker chemically

Jan 1, 1937

By J. Gordon Parr, A. J. Goldak

OgdEN et al.1 and Bumps et al.2 suggested that the solubility of aluminum in a titanium extended to 30 pct.* Sagcl,3 Clark and Terry,4 Anderko et al.,5 Ence and Margolin6 and Saulnier and croutzelles,7 subsequently proposed the existence of an intermetallic compound in the region of 25 pct Al. Although Anderko et al.5 suggested that the structure of this phase, Ti3Al, was of the DO,, (Ni3Sn) type, their conclusion was based only upon the results of a powder photograph that included reflections from ? = 0 to ?= 27° (CuK),some of which were reported to be indistinct. Ence and Margolin,6 referring to a 25 pct alloy (but without indicating whether the figure referred to weight or atomic pct) stated: "The structure of Ti2Al is isomorphous with Ti3Sn DO19, as pointed out by Pietrokowsky". But the point was not proven, because Ence and Margolin did not report values of calculated intensities of Ti2Al with the DO,, structure. In fact, the observed intensities they reported are in poor agreement with the values we calculate for DO19 (see Table I). Saulnier and croutzelle7 concluded, on the basis of electron micrography and microdiffraction studies, that the structure of the 25 pct A1 alloy was ordered hexagonal. Our purpose has been to unequivocally determine the Ti3Al structure. Alloys containing 25 pct Al were prepared from iodide titanium and spectrographic standard aluminum by levitation melting. The levitation chamber was evacuated to 10-6 mm Hg before filling with 99.999 + pct A. After casting, the alloy was chilled to liquid air temperature and crushed to -200 mesh in a percussion mortar. The powder, wrapped in molybdenum foil, was annealed (by induction heating) at 1000 "C for 2 hr in the argon atmosphere of the levitation chamber. No sublimate was seen on the foil or elsewhere, and therefore the assumption is

Jan 1, 1962

By AIME AIME

IV. THE BOUNDARY BETWEEN STEEL AND IRON. It would be well to decide on a definite carbon-content to serve as a boundary line between ingot-iron and ingot-steel, between puddled-iron and puddled-steel, and between any other varieties of wrought-iron and weld-steel. Two plans have been considered. One is to draw this line at 0.32 per cent. of carbon or its equivalent in other elements, for the reason that this carbon-content appears to correspond to the critical point, 0, in the diagrams of Roberts-Austen and Rooze-boom.8 This has the merit of corresponding to a definite physical boundary. The other plan is to draw the boundary at 0.20 per cent. of carbon, because this is a convenient place to separate the important classes " soft steel " and " half-hard steel," so that if this point was adopted "ingot-iron " would be synonymous with "soft steel," and " ingot-steel " would be the equivalent of the two classes, " half-hard steel " and " hard steel."

Mar 1, 1908

By J. R. Szedon, T. L. Chu, G. A. Gruber

Amorphous adherent filnzs of silicon dioxide have been deposited on silicon substrates by the oxidation of silane at temperatures ranging from 650 to 1050C. Various diluents (argon, nitrogen, hydrogen) were used to suppress the formation of SiO2 in the gas phase. Deposition rates of the oxide were determined over the temperature range in question as functions of' re-actant flow rates. Etch rate studies were used for a cursory comparison of structural properties of deposited and thermally grown oxides. From electrical evaluation of metal-insulator-silicon capacitors it was determined that the interface charge density of deposited films is similar go that of dry-oxygen-grown films in the 850° to 1050 C temperature range. Deposited films exhibit several ionic instability effects which differ in detail from those reported for thermal oxides. Stable passivating films of silicon nitride over deposited oxides appear to be practical for use in silicon planar device fabrication. Such films can be prepared under temperature conditions which have less effect on substrate impurity distributions than in the case of grown oxides. AMORPHOUS silicon dioxide (silica) is compatible with silicon in electrical properties and is the most widely used dielectric in silicon devices at present. Silica films can be prepared by the oxidation of silicon or deposited on silicon or other substrate surfaces by chemical reactions or vacuum techniques. The ability of thermally grown silicon dioxide films to passivate silicon surfaces forms one of the practical bases of the planar device technology. Properly produced and treated films of grown SiO 2 can have low densities of interface charge (-1 X 10" charges per sq cm) and can be stable as regards fast migrating ionic sgecies. 1 To maintain these properties, even with an otherwise hermetically sealed ambient, the Sia layers must be at least l000 A thick. Such thicknesses require oxidation in dry oxygen for periods of 7.8 hr at 900°C or 2 hr at 1000°C. Although oxidation in steam or wet oxygen can reduce these times to 17 and 5 min, the resulting oxides must be annealed to produce acceptable levels of interface charge., Oxidation or annealing involving moderate to high temperatures for extended periods of time can be undesirable. Under some conditions, there can be changes in the distribution of impurities within the underlying substrate. A chemical deposition technique using gaseous am-bients is particularly attractive and flexible for preparing oxide films. With a wide range of deposition rates available, films can be produced under condi- tions of time and temperature less detrimental to impurity distributions in the silicon than in the case of thermal oxidation. The pyrolysis of alkoxysilanes, the hydrolysis of silicon halides, and various modifications of these reactions are most commonly used for the deposition of silica films.3 Silica films obtained in this manner are likely to be contaminated by the by-products of the reaction, organic impurities, or hydrogen halides. The use of the oxidation of silane for the deposition process has been reported recently.4 The deposition of silica films on single-crystal silicon substrates by the oxidation of silane in a gas flow system has been studied in this work. The deposition variables studied were the crystallographic orientation of the substrate surface, the substrate temperature, and the nature of the diluent gas. The electrical charge behavior of Si-SiO2-A1 structures prepared under various conditions was investigated by capacitance-voltage (C-V) measurements of metal-insulator-semiconductor (MIS) capacitors. The experimental approaches and results are discussed in this paper. 1) DEPOSITION OF SILICA FILMS The overall reaction for the oxidation of silane is: The equilibrium constants of this reaction in the temperature range 500° to 1500°K, calculated from the JANAF thermochemical data,= are shown in Fig. 1. In addition to the large equilibrium constants, the oxidation of silane is also kinetically feasible at room temperature and above. However, the strong reactivity of silane toward oxygen tends to promote the nucleation of silica in the gas phase through homogeneous reactions, and the deposition of this silica on the substrate would yield nonadherent material. The formation of silica in the gas phase can be reduced by using low partial pressures of the reactants. Argon, hydrogen, and nitrogen were used as diluents in this work. 1.1) Experimental. The deposition of silica films by the oxidation of silane was carried out in a gas flow system using an apparatus shown schematically in Fig. 2. Appropriate flow meters and valves were used to control the flow of various reactants, i.e., argon, hydrogen, nitrogen, oxygen, and silane. Semiconductor-grade silane, argon of 99.999 pct minimum purity, oxygen of 99.95 pct minimum purity, and nitrogen of 99.997 pct minimum purity, all purchased from the Matheson Co., were used without further purification. In several instances, a silicon nitride film was deposited over the silica film. This was achieved by the nitridation of silane with ammonia using anhydrous ammonia of better than 99.99 pct purity supplied by the Matheson CO.' The reactant mixture of the desired composition was passed through a Millipore filter into a horizontal water-cooled fused silica tube of 55 mm

Jan 1, 1969

By Merrill, Charles White

MOST extraordinary of the technical developments in placer gold mining during the last five years has been the rise of the dragline dredge, by which is meant a floating washing plant for auriferous gravel, fed by a dragline excavator. The idea originated in the fall of 1933, when Horace Onyett constructed a floating washing plant to which gravel was delivered by a dragline excavator standing on dry land. Onyett's operation near Oroville, Calif., and another started by H. F. England later on Wyandotte Creek, Butte County, Calif., yielded '75 oz. of fine gold before the end of 1933. Although the first operation was abandoned shortly as un- profitable, the dragline-dredge method of gold recovery soon began to expand at a boom rate. As a matter of interest, the Onyett operation was taken over later by Lord and Bishop, who are re- ported to have succeeded in making it the first financially successful drag- line dredge. In California alone drag- line dredges produced $3,294,970 worth of gold in 1937, and the pros-

Jan 1, 1938

By O. D. Sherby, J. E. Dorn

For elevated temperature-constant load creep tests of a solid solution alloys, the creep strain is a function of a temperature-compensated time parameter 0 = je H/RT dt. The activation energy H is equal to o constant of about 36,000 cal per mol. The substructures resulting from a given creep stress condition are functions of the creep strain independent of temperature. Each new creep stress gives a new unique set of grain substructures; this is one of the factors responsible for the failure of the mechanical equation of state for creep. IN this report an attempt is made to correlate the creep properties of dilute a: solid solutions in aluminum with the subgrain structures that are developed during creep. The possibilities of such correlations have already been suggested by Wood et al. and others1-" who demonstrated that the subgrain structures are functions of the creep stress, creep strain, rate of creep, and temperature. Investigations by Sherby and Dorn' have shown that the creep strain, E, at constant load for dilute a solid solutions of aluminum is given by the functional relationship: e = f(8,u,) [1] where: 0 equals te-AH/RT = temperature-compensated time; t, time; AH, activation energy, - 35,800 cal per mol; R, gas constant; T, absolute temperature, above 400°K; and u,, initial creep stress. Consequently, it was anticipated that the subgrain structure that develops during a constant load creep test should also correlate with any two of the three significant variables C, 8, and Another possible correlation between the subgrain structure and the creep variables is obtained by differentiating Eq. 1 with respect to time, whence the creep rate, 2, becomes: = (2L) (2) =f (, u,) e-AHRT [2] or: e = F (c e H/RT, 0) [3] For the minimum creep rate, ;,, 8 is solely a function of U, as revealed by Eq. 1. Consequently, at the minimum creep rate Eq. 3 reduces to: = F (eAH/RT) [41 Correlations between U, and i, eAH/RT were found valid for solid solution alloys of aluminum where AH was a constant of about 35,800 cal per mol. The parameter ;, eH/RT is identical to the Zener-Hollo-mon parameter8," used by them in evaluating the tensile properties of copper and other metals. Eq. 4 suggests that the subgrain structure developed during secondary creep might be correlatable with either of the two variables 2, e H/RT or u,. Some of the solid solution aluminum alloys which were discussed in an earlier report' were also used in the present investigation. Sheets of these alloys were homogenized, cold rolled from 0.100 to 0.070 in. in thickness and then recrystallized to about the same grain size. Their chemical composition and grain size are recorded in Table I. Creep specimens were selected with their tensile axes in the rolling direction. The details for creep testing have been described10 and will not be repeated here. All creep tests were performed under constant load conditions. Experimental Results and Discussion Metallographic Structure of Creep Specimens: In order to obtain a preliminary concept of creep on the metallographic structure of high purity aluminum, the various ruptured specimens previously used to obtain the creep data for pure aluminum were polished and etched electrolytically in a dilute solution of fluoroboric acid. Oblique illumination was used to reveal the substructures which, for convenience, are shown in correlation with the vs. ;, eH/RT curve in Fig. 1. It is necessary to emphasize that the data for the curve refer to the various secondary stages of creep whereas the micrographs refer to the fractured creep specimens. Nevertheless a regular and systematic correlation is observed between E, eAH/RT (or the creep stress) and the micro-structure at fracture. For In (e, eAH/RT) = 42.3, which refers to creep at a high creep rate and a low creep temperature, the fractured aluminum specimen, as shown by the micrograph in the upper right-hand corner of Fig. 1, exhibited extensive deforma-

Jan 1, 1954

By G. R. Speich, D. J. Mack

The transformation of was studied by isothermal methods. At all temperatures, the ß transforms quickly to fine grained ß" which develops silver-rich striations. At higher temperatures the striations disappear, the final structure being Widmanstatten a in ß'. At lower temperatures, the striated ß" is consumed by pearlite nodules of a + ß' which in turn form the Widmanstatten a in ß'. The transformation is unlike any previously reported for a eutectoid. AS part of a general program of study on the eutectoid reaction, the Ag-Cd eutectoid seemed particularly attractive because the ß phase which undergoes the reaction is another of the typical "electron compounds," AgCd, having the disordered body-centered cubic structure. This work deals with the eutectoid which occurs at 50.5 wt pct Ag, and not with the eutectoid which has been reported at 42.9 pct Ag.' There has been no work reported specifically on the Ag-Cd eutectoid which was studied. The only information available on this eutectoid is that work done in the determination of the phase diagram. For the most part, the terminal portions of the diagram, Fig. 1, are well established; however, the region from 40 to 60 pct Cd is still somewhat in doubt. The X-ray evidence'..' in this region is in conflict with the results of thermal analysis. X-ray analysis3 does not show a polymorphic transformation at about 240°C as indicated by thermal analysis.1,5 Even the X-ray evidence, within itself, is confusing in this region of the diagram. One investigator2 reports the ß phase as hexagonal close-packed and has found three phases in the one-phase ß field. Other X-ray investigators"' ' report the ß phase as body-centered cubic. The authors believe that much of the confusion resulted from incomplete homogenization of the alloys. It was found that it takes almost a week to produce a completely homogeneous two-phase structure at 370°C. Another possible source of error is the volatilization of cadmium from the surface and cracks of the specimen during annealing with the possible formation of a cadmium-poor phase. The only metallographic data available on this eutectoid alloy are those of Durrant1 and Fraenkel and Wolff.5 his information is very limited. The phase diagram chosen as most nearly correct is that in the Metals Handbook," which is almost identical with the phase diagram suggested by Durrant.1 Materials and Procedure The alloy was prepared from high purity silver (999.5 plus fine) and high purity cadmium (0.02 Pb, 0.005 Cu, trace Fe). The metals were melted in carbon under a nitrogen atmosphere. Some cadmium was lost by volatilization but by remelting several times and adding cadmium a 200 g ingot of approximately eutectoid composition was obtained. Because the CdO fumes are quite toxic, the exit gas from the furnace was led through a water trap to condense the CdO. The ingot was homogenized at 650°C for 24 hr, no attempt was made to prevent decadmiumization. This resulted in a narrow decadmiumized rim on the ingot which was removed. Filings for analysis were obtained from cross sections of the ingot. Silver was determined by the Volhard thiocyanate method,? cadmium by difference. The ingot analyzed 50.8 pct Ag at the top of the ingot and 50.7 pct at the middle and at the bottom of the ingot. This alloy was only slightly hypo-eutectoid compared to the accepted value of 50.5 pct Ag and was used for the isothermal studies. It was felt that further attempts to adjust the composition might be futile because of the volatility of the cadmium. The ingot was sectioned to specimens approximately 3/4 x 3/4 x 1/8 in. These specimens were "austeni-tized" for 3 hr in air at 650°C to yield homogeneous ß and then quenched into a salt bath held at constant subeutectoid temperatures where the transformation

Jan 1, 1954

By V. D. Perry

Carlisle: Reno, let's start off by asking "When was the first day that you began working in your profession?" Sales: I began in Butte, Montana, on August 22, 1900 as an assistant engineer for the Boston & Montana Consolidated Copper and Silver Mining Co., and continued at that job for about a year. The general manager was C. S. Batterman, and the mines- Mountain View, Pennsylvania, Leonard, East Colusa, and one or two others-were part of Boston & Montana.

Jan 5, 1966

By P. Sen

Frequently during the processing of minerals very fine particles are generated which are difficult to recover by conventional separation techniques and are rejected with waste water from mills. A method has been evolved for the continuous recovery of such fines by allowing the suspensions to flow through a rotating cylinder. Theoretical analysis of the trajectory of particles have shown that the efficiency of separation increases with R.P.M., tube diameter, particle diameter and density. Experiments carried out with the overflow from a hydrocyclone containing particles in the size range of 2-10 microns gave a separation efficiency of 60-70% with an R.P.M. of 3500 of the rotating tube.

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