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By A. W. Jenike

A theory of gravity flow of bulk solids like ores, concentrates, coal is outlined and an example of design for unobstructed flow is given. Mass-flow and plug-flow patterns are defined and related to the geometry of the bin. The effect of these patterns on segregation, first in-first out flow, and caking is described. This paper is a report on the results from the AIME sponsored project "Flow of Bulk Solids" which was carried out under the author's direction at the Utah Engineering Experiment Station, University of Utah, during the period 1956-1962. The theory has been applied to the design of numerous industrial storage plants. A QUANTITATIVE METHOD OF DESIGN FOR FLOW There is hardly an industry which does not store and handle solid materials in bulk form. When the volume of the solids is large, gravity is invariably relied upon to cause the solids to flow out of storage, through channels and chemical reactors. Such materials as ore, coal, cement, flour, plastics, clay, soil, to which a general term of bulk solids is applied, flow by gravity or are expected to flow by gravity in thousands of installations and by billions of tons annually. The chemical and process industry depends on gravity flow of solids in process and out of storage. Mining relies on gravity flow in block-caving, in ore passes, as well as in storage and loading bins. Agriculture uses gravity flow in elevators, in feed plants, and in farm silos. In practice, satisfactory gravity flow is seldom attained. Such problems as doming, piping (rat-holing), lack of live capacity, segregation, deterioration in storage, harass industry. In spite of the universality of these problems, until recently, there has been no theory of solids flow, no method of predicting how a solid would behave, and how the channel, bin, or hopper should be designed. In the late nineteen forties and early fifties, the theory of plasticity came of age and simultaneously the computer became widely available. These two factors permitted the development of a theory of flow of bulk solids. The work was conducted during the years 1953-1961. In conjunction with the development of the theory a method to measure the flowability of solids was also developed1-7 and the theory was ap-plied to the design of ore pockets, storage plants,16 chemical reactors and adsorption columns. A comprehensive report of this work is given in a previous work." THEORY OF FLOW The most important question which a theory of flow has to answer is: what conditions need to be satisfied for a given solid to flow uniformly and without obstructions through a channel? First of all, the following observations are made:

Jan 1, 1967

By H. U. Schutt, J. M. Toguri

REGARDLESS of the degree of purification effected during the electrorefining of copper, a danger of re-introducing impurities exists in the operation of melting and casting of the refined copper. Logically only a combination of the purification and casting operation would remedy the situation. A well-known method of metal purification is the "Gross"-type process, whereby a volatile halide is produced, purified, and decomposed.' In the present case, this concept was used to remove the impurities rather than to form possible volatile copper halides. The object was to produce volatile halides of the impurities present and distill these away, leaving high-purity copper. It is interesting to note that such techniques are used in spectrographic procedures in order to shorten exposure time and enhance the density of impurity lines.' In the present investigation, copper hydroxy fluoride was used, since the temperature of decomposition of copper hydroxy fluoride and the melting point of copper nearly coincide. The fluorine released by the thermal decomposition of copper hydroxy fluoride purges the molten copper. Copper hydroxy fluoride was prepared by dissolving high-purity copper in nitric acid and adding hydrofluoric acid and ammonium hydroxide in the required proportions. The melt was made in a high-purity graphite crucible heated by an induction furnace. Trial experiments showed that impurities can be introduced from the crucible material. Therefore, preceding each cast, the crucible itself was cleaned by decomposing copper hydroxy fluoride and discarding the residual copper. Best experimental conditions were obtained by adding 30 g of copper hydroxy fluoride to 500 g of nor-

Jan 1, 1967

By Robert G. Pinkerton

Boyles Bros. Drilling Co. and Gibbons and Reed Company, both of Salt Lake City, Utah, have successfully combined into two joint ventures on the San Juan-Chama project of the U. S. Bureau of Reclamation. The Azotea Tunnel is 12.7 miles in length; the inlet portal is on the Navajo River in Archileta County, Colorado, and the outlet portal is in New Mexico, about 10 miles south of the state border. The Oso Tunnel lies immediately to the north of the Azotea Tunnel and discharges water directly into it. We are presently driving both tunnels with mechanical boring machines from their portals at the Navajo River. Both tunnels are circular, fully concrete lined. The Azotea Tunnel has a finished diameter of 10 ft. 11 inches while the Oso Tunnel is 8 ft 7 inches in diameter. Both tunnels are supported with circular, structural steel rings as required by ground conditions. In good ground rock bolts and steel roof plates are used.

Jan 1, 1967

By Franklin D. Slagle

Porosity and bulk-and sand-grain-density values were determined for 2,040 core samples of 30 formations from 47 wells in New York, Ohio, Pennsylvania, and West Virginia, and are compiled for petroleum industry use in well-log evaluation and geologic studies.

Jan 1, 1967

By W. A. Calhoun

Progress made in a second and final metallurgical investigation made by the Bureau of Mines of near-surface Hawaiian bauxitic deposits from Kauai, Maui, and Hawaii Islands, and on a deeper deposit from Kauai, is reported. Previously reported Al2O3 extractions were increased by modifying conventional processes to fit the ore being tested. Increases in Al2O3 extraction were: Kauai, from 82.8 to 95.4 percent; Maui, 85.5 to 94.1 percent; and Hawaii, from 79.5 to 86.4 percent. Use of a "caustic-reduction sinter, leaching, and magnetic separation process" for Al2O3 extraction also produced an iron concentrate of commercial grade, except for titanium content. No successful method was developed for the recovery of a satisfactory titanium concentrate.

Jan 1, 1967

By Klaus Schwerdtfeger

Activities of lead in Pt-Pb and Pd-Pb melts in the temperature range of 800° to 1200°C have been detev-mined from electromotive-. force measurements 202th the cells Both systems display strong negative deviations from Raoult's law. The data obtained with cell [1] were combined with available data on the activity of PbO in silica-satuvaterl PbO-SbO2 melts to calculate the standard free cnergy of formation 01- liquid PbO. FREE energies of formation of oxides and activities of components in metal and oxide melts can be determined with galvanic cells consisting of a metal phase, an electrolyte containing the oxide of one of the components of the metal phase, and an oxygen electrode. This technique has been used previously to measure the standard free energy of formation of solid sio2, 1 and activities in Fe-si, CO-si,2 Ni-Si,2 and CaO-P2O5 3 melts. The present paper reports activities in Pt-Pb and Pd-Pb melts as measured with the same experimental technique. EXPERIMENTAL METHOD General Considerations. The following cells were used: Pbl (PbO-SiO2)liquid, SiO2 Pt-Pb 1 (PbO-SiOz)liquid, SiO2solidO2 [2] Pd-Pb (PbO-SiOz)liquid, SiO2solid O2 [3] Liquid alloy and' oxide melt were contained together in a silica glass crucible of essentially the same design as described previously.1'2 The PbO-SiO2 melts are ionic conductors.' During the experiment, the silica glass crystalizes in a layer adjacent to the electrolyte. The electrolyte equilibrates with solid silica and hence attains the composition of the Si02-liquidus curve in the system PbO-SiO2 at any particular temperature. Molybdenum wires were used to establish contact with the liquid metal. The oxygen electrode, which reaches the surface of the PbO-SiO, electrolyte from above, consists of a platinum wire inserted into a ceramic tube and provided with a 2-mm-diam platinum bead at its end. Gas of known oxygen partial pressure (pure oxygen of 1 atm: air, or N2 with 1.04 pct 0,) is blown through the ceramic tube onto the surface of the electrolyte. The cell reaction is Pb (metal) + 1/2O2 (gas) = PbO (electrolyte) [4] No oxidation of platinum or palladium ("displacement reaction") occurs. This is to be expected from the noble character of platinum and palladium, but was also shown experimentally, as described in the next section. The galvanic electromotive force of the cell is given by where AG is the change in free energy for Reaction [4], E(=2) is the number of electrical equivalents necessary to form 1 mole of PbO, and F is the Faraday constant. Formula [5] is valid only if no junction potential exists within the electrolyte. Junction potentials occur only when the compositions of the electrolyte are markedly different at the electrodes. Such differences are negligible in the PbO-SiO, electrolyte, as shown in the next section. Since molybdenum contact leads are used, appropriate corrections were made on the measured electromotive forces to account for the thermoelectric effect of the Mo-Pt couple. The thermoelec-tromotive forces were measured separately with a Mo-Pt couple, and were found to vary linearly from 19 mv at 740°C to 40 mv at 1310°C with molybdenum being positive and platinum negative (cold junction at 25°C). Extrapolation of these values to higher temperatures yields values which are in satisfactory agreement with those obtained previously in the temperature range 1440° to 1630°c.1,2 The change in free energy for Reaction [4] is expressed as where chemical potentials of the species. The value of constant for a given temperature because the slag composition is fixed. Inserting [6] into [5] and using appropriate expressions for upb and uO2 the relation

Jan 1, 1967

Jan 1, 1967

By G. L. Schroeder

Investigations were conducted at two underground locations, foreman's room and 5702 area, of the Kermac Nuclear Fuels Corp. uranium mining installation, Ambrosia Lake, New Mexico. The rock environment is stratified sandstone. Pressures were varied from minus 0.4 an Hg to plus 3.8 cm Hg with respect to barometric pressure, and were maintained for periods ranging from several hours to 21 days. One cm Hg overpressure (-1.5% of normal barometric pressure) produced a 20-fold decrease in Rn flux into the foreman's room as compared to the Rn flux observed during dilution ventilation. The 5702 area experienced a 5-fold decrease in Rn flux for a similar overpressure. During 21 days of continuous 1 cm Hg overpressure in the 5702 area this reduced Rn flux was maintained. The smaller reduction in flux for the 5702 area results in part from the proximity of the foreman's room to a non-pressured area and the presence of an impermeable shale lens overlying the ceiling of the 5702 area. A 0.4 cm Hg underpressure of the 5702 area increased the Rn flux into the area by 3-fold over the non-pressured value. A barometric pressure influence on Rn flux into the mine and on air Rn concentrations in non-pressurd areas of the mine was measured. A falling barometric pressure causes an increase in the flux of interstitial gas into the mine; a rising barometric pressure decreases this flux. These effects are not seen in overpressured mine areas. Radon concentrations in rock interstices show, during overpressure, decreases of all locations monitored except in the immediate vicinity of the shale lens above the 5702 area ceiling. These reductions are the result of air flowing from the mine into the rock interstices under the influence of the pressure gradient induced by the overpressure. The relative humidity of the 5702 area was reduced after 2 days of 1 cm Hg overpressure from a pre-overpressure value of 96% to 81%. The control of harmful or noisesome gases which emanate into underground mining areas from surrounding rocks is often a costly necessity. In uranium (U) mines this problem is presented by the high interstitial concentrations of radon-222 (Rn), a radioactive noble gas of 3.82-day half-period, formed in the decay scheme of U238, and the relative ease with which this noble gas diffuses from its parent rock into the interstices of the rock and then to a working area. Long-term exposure to moderate concentrations of Rn (3000 µµc per 1) and its short-lived alpha-ray emitting daughter products, RaA (Po218) and RaC (po214), has been found to result in an increased incidence of bronchial carcinomaa2 The acceptable limit of Rn daughter products in a mine atmosphere is presently set at a concentration of short-lived radon daughters which would be in equilibrium with 100 ppc of Rn per 1 of air. Ventilation of mines is conventionally accomplished by continuously diluting the mine air with fresh air brought in by fan or natural convection from above ground surface. The diluted air is allowed to vent freely to the atmosphere. This process does nothing to retard the rate at which gases (including Rn) diffuse into the mine from surrounding rock. It merely reduces the concentrations of these gases within the mine. It is suggested that in a sufficiently permeable rock environment a slight pressurization of the mine air may induce air flow from the mine into the interstices of rock surrounding the mine. The convective flow of comparatively fresh air will reduce the concentration and the concentration gradient of undesirable gases in the rock interstices adjacent to the mine. Radon will diffuse counter-current to this convective flow at a rate proportional to its concentration gradient. In time, a steady state of convection and counter diffusion will be established. The Rn flux into the mine will never be reduced to zero, and will only asymptotically approach zero as the overpressure (and hence the convective velocity of purging air) approaches infinity. During 1963 and 1964, an investigation into the effect which such applied pressures have upon the Rn characteristics of a mine atmosphere was conducted at the Kermac Nuclear Fuels Corp. uranium mines, Ambrosia Lake (near Grants), New Mexico.

Jan 1, 1967

By Jr. Fish

As a part of a study of iron are resources in the Appalachians, 9 diamond drill holes aggregating 1,580.7 feet were drilled in a portion of the Butt Mountain area of northeastern Giles County, Virginia. Three hematitic sand-stone beds were intersected in the Clinton formation but only one was consistent in thickness and grade in all 9 drill holes. This bed averages 18.9 percent iron over an average thickness of 24 feet. The drill cores were logged and chemical analyses were made on 161 individual samples and 22 composite samples. Beneficiation studies were made of three composite hematitic sandstone samples each representing a separate bed containing 14.6, 19.8 and 20.0 per-cent iron. Major mineral constituents of the samples were hematite, quartz, and sericite.

Jan 1, 1967

By K. G. Davis

Dilute alloys of silzer in tilz haz been solidzjzed a1 controlled rules, in lzorizontal tubes 2 mrz and 0.5 rn in diam. Radioactive; tracer techniques we?-e used to study solute distvihutions along llze specimens and irmpurity substructures, as functions of the conditions growth. The results have heen mzalyzed using Burton, Prim, and Slichter's tnodel for the solute disty-ihution in the liquid ahead of an advancing solid-liquid interface. DECANTING techniques have been used to establish criteria for the formation of impurity substructure during solidification in several alloy systems An analysis equating the appearance of impurity substructure with the incidence of constitutional supercooling was developed,= in which diffusion was assumed to be the predominant mode of solute mixing in the liquid. Substitution of experimental data into the equations derived from the diffusion analysis gave reasonable values for solute diffusivity in the liquid. However, in these investigations solidification rates of 10 cm per hr and over were used, to minimize the effect of natural conection, whereas for crystals of high perfection lower solidification rates are needed, usually between 1 and 5 cm per hr. A knowledge of the conditions under which impurity substructures will be formed at low growth rates, and the degree of segregation to be expected, is therefore of interest. In the present investigation, radioactive-tracer techniques have been used to study the effect of growth rate, initial solute concentration, and size of specimen on the formation of substructure in uni- directionally solidified rods of dilute silver in tin alloys, over a range of growth rate between 0.5 and 10 cm per hr. Criteria for the formation of substructure were established by auto radiography. This was believed preferable to the decanting technique, for the relationship of the structure on a decanted interface with that of the freezing interface is not clear, since a layer of liquid is left on the surface following decanting.' The effect of substructure on the distribution of solute along the rods was also investigated. EXPERIMENTAL The procedure for sample preparation has been described in detail by einber. Alloys were prepared from tin of 99.999 pct purity and silver of 99.99 pct purity. A"', an emitter of both y and 0 radiation, was used as tracer. Samples of the alloys were drawn up into silica tubes with inside diameters 0.5 or 2 mm, remelted in a horizontal furnace, and solidified at controlled rates. A few centimeters of the samples were left unmelted for a measure of the initial concentration. Total sample length was approximately 20 cm. The temperature gradient in the furnace was kept constant at 36°C per cm in the region corresponding to the melting point for tin. To find how well this corresponded to the actual temperature gradient in the melt, a thermocouple of 38-gage wire was electrically insulated with a thin layer of Sauereisen cement and placed within one of the 2-mm-diam tubes, which was then filled with tin. The maximum diameter of the coated wire was 0.5 mm, the bead of the thermocouple junction being no larger than the diameter of the wire. A plot of temperature vs distance traveled by the furnace is given in Fig. 1 for a rate of furnace travel of 1 cm per hr. The temperature gradient in the liquid

Jan 1, 1967

By R. W. Parsons

The over-all apparent single-phase permeability of fracture-rock systems was studied using two different two-dimensional models. In a strict sense the results are applicable only to these models, yet may give some insight into real reseruoir behavior. The regular fracture-matrix model can have any number of regular fracture sets. All fractures within each set have the same orientation, width and spacing. The gross behavior is amlytically equivalent to that of an anisotropic permeable medium. In the heterogeneous fracture systems, individual fracture conductivities vary within a two-dinensioml network pattern. A computer program calculates the overall permeability after the conductivities are randomly placed in the network. The calculated permeability depends upon the distribution of these conductivities and the particular fracture pattern into which they are placed. Although detailed information on actual reseruoir fracture systems is not available, this study shows how some of the possible variables may affect obserued gross reservoir characteristics. INTRODUCTION Characteristics of reservoir rocks are determined by direct (core analysis) or indirect (logging and production tests) examination. Both methods, singly and together, are widely used in reservoir evaluations. For fractured reservoirs a problem exists in relating characteristics of cores to the in situ reservoir properties. Knowing fracture characteristics can be of value in determining production mechanisms. Because of the limitations of observation, the intimate details of a fractured rock system will never be known. One approach in analyzing fractures is to study the behavior of some conceptually simple models. The two models analyzed contain features which may be realistic, yet are mathematically tractable. Flow is considered in two dimensions only, with the plane of interest at right angles with the fractures. This concept represents the horizontal flow in a reservoir system with the fractures oriented vertically. Only single-phase, laminar flow is considered. The regular fracture-rock system permeability is calculable from a simple analytical expression. The heterogeneous system requires a computer program for calculating overall permeability.

Jan 1, 1967

By K. H. Coats, M. H. Terhune

Analysis and example applications have been performed to compare the accuracy and computing speed of alternating-direction explicit and implicit procedures (ADEP and ADIP) in numerical solution of reservoir fluid flow problems. ADIP yields significantly greater accuracy and requires about 60 per cent more computing time than ADEP, not 300 or 500 per cent more as reported elsewhere. l,2 INTRODUCTION Several recent papers 1-3 discuss an alternating-direction explicit difference approximation (ADEP) to the diffusion equation. Example applications of ADEP and ADIP4 were reported to support conclusions that ADEP is comparable in accuracy to ADIP and requires one-fifth to one-third the computing time of ADIP. Applications of ADEP in calculation of two-phase flow in reservoirs was also proposed. 3 This study was performed to compare further the relative merits of ADEP and ADIP in simulation of two-dimensional flow of one and two fluid phases in reservoirs. Since two-phase flow equations are often essentially elliptic rather than parabolic, the efficiency of ADEP in solving the elliptic equation was also examined.

Jan 1, 1967

By L. A. Wilson, P. J. Root

The relative costs of heating a reservoir by steam injection and by combustion have been examined. The comparison was based on a model similar to that proposed by Chu.' The cost of boiler feed water, the price of fuel, pressure and plant capacity were parameters in determin-ing the costs of air compression and steam generation. The analyses compare the cost of heating to the same radius by the two methods. Results suggest that the two primary factors for comparison are the price of fuel and the amount of crude burned during underground combustion. The cost of fuel has a greater effect on the cost of heat from steam than it does on its cost by combustion. As a result, analyses indicate that when the price of fuel is low, steam may be unequivocally cheaper than air. The influence of heat loss is such, however, that as the heated radius increases combustion becomes relatively more competitive depending upon the amount of crude burned. This implies that steam may be cheaper for small stimulation jobs (huff and puff) but combustion may be more economically attractive for heating large areas (flooding). INTRODUCTION Use of thermal methods of recovery is an accepted fact today. After an induction period of several years, processes are being widely used that involve reservoir heating to augment recovery. Of the several techniques, steam injection and forward combustion appear to be destined to dominate the field. Although the objectives of both are the same, the basic differences between generating heat in situ and injecting heat after surface generation influence the cost in different ways. This study compares the cost of heating a reservoir either by steam injection or by forward combustion. There has been no consideration of recovery. Presumably, recovery from the swept region would be high in either case. The sole consideration was the cost of heating to the same radial distance by either process. PROCEDURE THE MODEL The basis for comparison was a mathematical model similar to that used by Chu' for combustion. The model simulates a radial heat wave in two-dimensional cylindricaI coordinates. It includes heat generation, conduction and convection within the reservoir and conduction in the bounding formations. Thus, heat losses from the formation are considered. Three significant modifications were made. 1. Equal logarithmic increments rather than equal increments were used for the mesh spacing in the r direction. By this technique large distances were simulated with relatively few mesh spaces. 2. A backward difference approximation to the convection term was used to avoid troublesome oscillations which result from a central difference approximation when the convection term is large. 3. The radial increments of the combustion zone motion were not necessarily uniquely related to the mesh configuration. The cumbersome step function introduced by the heat of vaporization of steam was circumvented by assuming the enthalpy of the steam to be a linear function of temperature between reservoir temperature and steam temperature. This is equivalent to assuming an average heat capacity numerically equal to the difference between the enthalpy of saturated steam and the enthalpy of water at reservoir temperature divided by the difference between the two temperatures. Heat losses obtained by this model are in essential agreement with those obtained by the analytical solution of Rubenshtein.' A detailed description of the model is presented in the Appendix. Using the model, the times required to heat to particular radial distances were obtained as a function of injection rate and other physical parameters. For the steam case, injected fluid was assumed to be saturated steam at pressures of either 500, 1,000 or 1,500 psia. The corresponding temperatures are 467, 544 and 596F, respectively. Thickness ranged from 10 to 50 ft and injection rate ranged from 100,000 to 1 million Ib/D. Reservoir and overburden temperatures at the injection well were assumed to be that of saturated steam at the injection pressure. The effect of maintaining the overburden temperature at the well at a different temperature (initial reservoir temperature) was examined with no significant change in behavior. The influence of wellbore heat losses for the steam case was determined in the following manner. The rates of heat loss as a function of time were estimated using an approach similar to that suggested by Ramey." he data were based on injection through 2%-in. tubing in 7-in. casing. Integration of these data over the entire iniection period yielded the total heat loss. Total heat losses were then corrected to their equivalents in steam (this number resulted from dividing the total heat loss by the latent heat). This was considered additional steam required to accomplish the reservoir heating and the total cost was increased accordingly.

Jan 1, 1967

Jan 1, 1967

Table 1.-Salient statistics of carbon black produced from natural gas and liquid hydrocarbons in the United States [ ]

Jan 1, 1967

By C. S. Simons, G. Major-Marothy, M. A. K. Grice, D. A. Dahlstrom

The vacuum filter operating variables that influence cake moisture are discussed. The influence of temperature control, particularly through application of steam to the cake, is emphasized. Results of pilot plant studies on filtration of fine hematite concentrates are presented and discussed, and are shown to support the theoretically-derived conclusions. Results on fine magnetite concentrates are also used to support the argument. The relative merits of disc and drum filters from the standpoint of cake moisture are discussed. Moisture content has always been recognized as one of the most important properties of concentrates used as pellet plant feed. Most iron ore concentrates are produced by wet methods, and are finally de-watered on filters. Obviously, a real economic advantage accrues to the ability of control the moisture content of the filter cake within the range required for optimum pellet production. Another consideration, also, has been receiving increasing attention recently. Transoceanic shippers of concentrate cargoes are critically assessing the hazards of excess moisture. The nature and magnitude of these risks have been described, ' and it appears that their elimination may require that residual moisture be somewhat lower than the limit for proper pelletization. Coarse, very free-filtering materials, such as the products of spirals, are usually best handled on top-feed types of machines. The moisture content of the cake may be held at a specified value by proper design and operation, taking into account cake thickness, air-flow rate, and drainage time. Fine-grained concentrates, with which we will be concerned here, must be filtered on Drum or Agidisc machines. With many of these materials, it is possible, by proper design, to meet cake moisture requirements with a conventional filter station. The first installations to produce high-grade pellets from magnetic taconites fell in this class. In fact, the design criteria were developed in connection with operations of Reserve Mining Co. at Silver Bay, inn.,2 and these have been verified repeatedly in other mills. The trend today, however, is toward the production of more difficultly dewatered concentrates. This is due on the one hand to the increasing attention being given to non-magnetic ores, which tend to be far slimier, and therefore much more retentive of moisture, than the magnetites. On the other hand, the pressure to improve the grade of the magnetic ores is leading to finer grinds, which also are more difficult to dewater. In the latter case, the decision to improve grade in an existing operation by finer grinding for better liberation may lead to two unattractive alternatives: 1) substantially higher bentonite consumption, plus the risk of poorer quality pellets, from high cake moisture, or 2) installation of a thermal dryer. There is, however, a third alternative. In recent papers by two of the authors3,4 it was shown that for many materials a significant decrease in cake moisture can be obtained by applying live steam to the cake face during the drying part of the filter cycle. Further, this limited drying appears to have distinct economic advantages compared to thermal drying. It is the purpose of this paper to explore the third alternative. To do this, the results of an extensive pilot study of steam filtration of a hematite flotation concentrate will be critically examined. This study was sufficiently broad so that a number of alternate suggestions (besides steaming the cake) for reducing moisture content were tested, and comparative data for both Drum and Disc filters were obtained. The work was particularly interesting since the concentrate has a high Blaine surface, and is therefore particularly difficult to dewater to the levels required. FILTER CAKE MOISTURE The significant difference between concentrate filter cake as discharged from the filter, a cargo of that same filter cake during or after shipment, and a green ball formed from that filter cake is in the relative volume of voids, or porosity. In every case, the material is a collection of small solid particles held together by the cohesive forces of a liquid. The physical properties of the aggregate are determined by the

Jan 1, 1967

By D. N. Seidrnan

In the present note we present thermal-analysis data for the liquidus curve from 0 to 76 at. pct Se and for the selenium-rich monotectic reaction in the Pb-Se system. We have previously reported that no expey-imental eviderzce was found for a lead-rich monotectic reaction, at -860°C with a monotectic composition of -20.5 at. pct Se, as found by Nozato and Igaki.&apos; Our additional data substantiated this earlier finding and extended the composition range studied. The alloys were prepared from semiconductor -grade lead and selenium purchased from the American Smelting and Refining Co. Both elements were 99.999+ wt pct pure as determined by the supplier. The impurities for lead were Fe (1 ppm) and Cu & ppm) while for selenium the impurities were Cu (< 1 ppm), As (< 1 ppm), Te (1 ppm), and C1 (<1 ppm). The general procedures used for thermal analysis were those specified by the National Bureau of Standards. A Pt/Pt-10 pct Rh thermocouple calibrated against the freezing points of zinc and copper purchased from the National Bureau of Standards and antimony (99.985 pct pure) purchased from A. D. Mackay, New York, was used for all the thermal analysis. The thermocouple electromotive force was measured with a Rubicon Type B potentiometer used in conjunction with a galvanometer with a sensitivity of 0.5 pV (mm) -&apos;. The absolute accuracy of this thermal-analysis system was *0.5"C. One-hundred-gram alloys of the desired composition were sealed in quartz crucibles, with a central thermocouple well, at a pressure of less than 10"1 Torr. The alloys were initially heated well above the liquidus curve and shaken vigorously to insure homogeneity. Cooling curves were then taken by the direct method at cooling rates ranging from -0.5" to 1.5"C (min)-&apos;. The phase diagram from 0 to 76 at. pct Se as determined by direct thermal analysis is shown in Fig. l.* An extrapolation of the selenium-rich portion of the liquidus curve to the monotectic reaction isotherm (678.3"C) gave a value of 76.1 at. pct Se for the monotectic composition. A tabulation of all the thermal-analysis data is given in Table I. As we previously reported no experimental evidence was found Fig. l—The partial Pb-Se phase diagram from 0 to 76 at. pct Se as determined by direct thermal analysis. For the sake of clarity the points for the 49.00 and 49.16 at. pct Se alloys were not drawn on this phase diagram, see Table I. for the lead-rich monotectic reaction found by Nozato and Igaki.&apos; This result was further substantiated by the fact that none of twelve lead-rich alloys, see Table I, examined for this monotectic reaction exhibited a thermal arrest in the temperature range (849" to 863°C) cited by Nozato and Igaki for the lead-rich monotectic reaction. Hence, our results tend to support the earlier qualitative work of ~elabon&apos; and Friedrich and ~eroux" in the 0 to 50 at. pct portion of the phase diagram, though the selenium-rich monotectic composition and reaction isotherm temperature were in agreement with the approximate values (75 at. pct Se and 672" to 680°C) given by Nozato and ~~aki. &apos;

Jan 1, 1967

By J. M. Stuve

The standard heats of formation (?Hf°) of holmium trichloride and terbium trichloride were measured by solution calorimetry. Heats of solution of holmium and terbium metals and their anhydrous chlorides were measured in 4.360 molal HCI at 298.15° K. From these measurements ?Hf° for HoC13 (c) was calculated as -240,290 ±1,700 cal/mo1e, and ?Hf° for TbC13 (c) was calculated as -238,330 ±1,500 cal/mole at 298.15° K.

Jan 1, 1967

By O. R. Bergmann

Two approaches were taken to obtain direct experimental evidence jar the existence oj a jet in the explosion-cladding pvocess: 1) direct observation of the claddirg jwocess by rtzeans ojf kig-h-speed photography using a fvartziiy catnera and 2) use of a plated-surface experiment in contribution with clzetrzical analysis. The framing-camera records showed clearly the presence of a jet it1 the form of what appears to be a line spray. The jet velocity is considerably highev than the detonation velocity arid in vacuum it is almost twice as high as the detonatiou velocily. The results jrorrz the plated-surface experiment also corzfivtned the preseizce of- a jet. The artzoutlt o,f etzergy dissipated in the jetting process was foundd lo be consislent with the basic theovetical model o/ the cladding mechanism.. MaNY reports on metal working with explosives have appeared in the literature during the last few yearsThis paper describes experiments concern- ing the mechanism of the explosive metal-cladding process. It has become increasingly important as a unique method for bonding metals and a typical cladding arrangement is shown in Fig. 1. A theoretical analysis of the mechanism of explosive bonding and a description of the nature and types of bond zones obtained was given by Cowan and oltzman." A further discussion of the basic principles of the process, a detailed description of the different bond-zone types, and extensive information on the properties and the applications of explosively bonded metals was recently published by Holtzman and cowan. " The process is now in commercial use by E. I. du Pont de Nemours & Co. The concept of the existence of a jet during metal bonding with explosives forms a central part in the theoretical analysis of the cladding mechanism described by Cowan and Holtzman When a layer of explosive is detonated on a metal plate that is separated from a second metal plate by a small distance the metal plate in contact with the detonating explosive is accelerated by the detonation pressure. An angle is established between the undeflected and deflected portions of the plate. Subsequently the deflected portion of the first plate collides with the second metal plate.

Jan 1, 1967

By E. Lifshin, R. E. Hanneman

QUANTITATIVE applications of the electron micro-beam probe frequently involve the evaluation of complex mathematical expressions and/or the analysis of large amounts of experimental data. The purpose of this communication is to describe briefly a versatile and useful computer program system that is applicable to analyze rapidly a wide variety of practical microprobe problems. This system consists of a group of ten FORTRAN programs that can be stored on tape, cards, or in the memory disc of the computer. These programs, or links, can be run individually or in any prespecified sequence without interrupting the operation of the computer or without destroying information which is being transfered from one link to another. For the program system described here a GE-235 computer with disc storage was used, so that the DCHAIN method of program linking was employed. Included in the library are programs to: 1) initiate analysis of a new set of data and transfer control between all other programs in any predetermined manner; 2) generate theoretical calibration curves of composition vs relative intensity; 3) generate empirical deviation parameters from least-square fits of experimental calibration data from standards of known composition; 4) convert raw X-ray data to corrected composition; 5) determine inter diffusion coefficients by Matano analysis of con centrat ion -distance data on a uniaxial diffusion couple; 6) determine activation energies and frequency factors of temperature-activated processes such as diffusion; and 7) generate calibration curves for determination of the thickness of thin films using microanalysis. A detailed description of these computer programs and their underlying principles is available on request from the authors."&apos; The first program to generate theoretical calibration curves of corrected relative intensities vs composition uses the Poole and Thomas atomic number correction&apos; and the Philibert absorption factor&apos; with a voltage-dependent mass absorption coefficient for electrons in the alloy. A modified Castaing fluores- cence correction is also used which includes the effects of both Ka and KO radiation and over voltage.&apos; Once the theoretical curves have been calculated in 1 wt pct intervals, these results are least-squares fit to obtain Ziebold deviation parameters&apos; which are stored in COMMON in the computer memory. The net discrepancies between the original theoretical calibration curve and the regenerated curve using the Ziebold parameter are computed. Although this link is explicitly written for K-K fluorescent interactions, it can be applied to K-L, L-K, and L-L interactions as previously disc~ssed."~ Similar programs have also been written to utilize the Wittry fluorescence correction, Birks combined corrections, and various other corrections.&apos; These modified programs have proved to be quite useful for quantitative comparisons of the results of the various theories. The program for conversion of raw X-ray data to corrected composition includes corrections for drift, backround, and instrumental dead time. The corrected intensities are converted to composition by use of the Ziebold equation"2 and parameter obtained from the program system. The results can be obtained for either atom or weight fractions. In addition to accurately computing interdiffusion coefficients the Matano analysis program calculates least-square smoothed values of concentration, concentration gradient, and curvature for each point on the raw input concentration profile. In order to obtain high accuracies a unique method of performing a least-square polynomial fit to incrementally advancing profile segments which overlap is used.&apos; This program has been successfully modified for use in ternary diffusion problems3 and can readily be modified to handle analysis of diffusion profiles which include phase boundary discontinuities. This link is generally applicable to analysis of interdiffusion data obtained by other techniques as well as by the microprobe. The primary function of the next program is to least-squares fit experimental diffusion data to the normal Arrhenius function: D = Doexp(-Q/RT), to obtain values of Do and Q. In addition the probable error and one, two, and three u statistical confidence limits of DO, Q, and log D are evaluated. This program is also directly useful for analysis of any other simple temperature-activated processes including conductivity, and certain deformation and chemical processes. The program to generate calibration curves for film-thickness determination using the microprobe is based on a numerical integration of the equation derived by Cockett and ~avis.&apos; Values of film thickness obtained by this program for copper on various substrates are in good agreement with measurements made by other techniques. Versions of the above program system have been prepared for use with or without a remote teletype connection to the computer for processing on either a real-time or time-share basis. The instrumentation coupling a microprobe to a teletype for automatic data collection and analysis by the presently described program system has been reported elsewhere by the authors.&apos; If teletype equipment is not used to communicate with the computer, standard methods of card reading and tape reading can be used. In either

Jan 1, 1967