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By Fred C. Bond

THEM is acute need for a method that will measure the size distribution of finely divided materials, particularly when the particle sizes are smaller than the openings of the finest screen cloth regularly available for testing. Several methods and types of apparatus are in common use, but none are entirely satisfactory for all purposes. The commonest methods are microscopic grain counts, elutriation by liquids or air, and sedimentation. Valuable results have been secured by air elutriating devices, typified by the Haultain Infra-Sizer and the Pearson Air Analyzer. These are especially useful in obtaining sized fractions that can be examined and analyzed separately. They are particularly advantageous because the sizes of the samples produced are adequate for a considerable amount of subsequent manipulation and testing. The sedimentation methods, such as the Wagner and Klein turbidimeters, and the sedimentation balance, do not deliver sized fractions, but they do provide a means for reasonably rapid comparative determinations of fineness and surface area, which are important in many industries. The sedimentation balance consists essentially of a balance pan suspended in a liquid that contains falling particles. These are weighed as they settle onto the pan, and the time rate of settling is determined. The size distribution is computed from the settling rate. The balance appears to be inherently more accurate than any of the other methods, and it has served a useful purpose in the study of numerous problems, but there have been limitations which have restricted its scope of application. Because of the essential simplicity of the method, it was felt that intensive investigation might lead to modifications that would make it a valuable tool for the operators in industries that require precise information regarding the results secured from grinding equipment. A large number of size-distribution determinations below 200 mesh were required in connection with a particular research problem in fine grinding. The sedimentation balance was used in this investigation, and a technique was gradually developed that ultimately gave good results. A serious difficulty appeared early in the work. It was discovered that less material always settled on the sedimentation pan and more on the bottom of the containing jar than could be accounted for by calculation, and also that the material that settled to the bottom of the jar outside the edges of the pan was considerably finer than that on the pan. This segregation was so great that the distribution obtained for the finer sizes was obviously very much in error; material ground to about the degree of comminution of cement might have only 60 per cent of the calculated weight actually settling on the pan, and the error increased with the fine-

Jan 1, 1939

By J. J. Arps

This paper is a study of the effect of temperature on the electrical resistivity of sodium chloride solutions based on the published resistivity and density data in the International Critical Tables. This temperature effect is of considerable importance in quantitative interpretation of electric logs, where it is frequently necessary to correct mud resistivities measured under surface conditions to temperatures existing at the bottom of the bore hole. An empirical approximation formula was developed for this conversion which has proved to be very useful and seems to provide results well within the range of accuracy of the data involved. This approximation formula states: sistivities of sodium chloride solutions at temperatures of t and t degrees Fahrenheit, respectively. INTRODUCTION Research by various investigators during the past 20 years has clarified the physical principles of the phenomena which cause the natural or spontaneous electric potential in rotary drilled bore holes. The basic relationship which is most commonly used reads: in which the SP deflection, as measured from the shale base line, is expressed in millivolts. K is a constant, which appears to vary between 50 and 110; the low value applying to shaly sands, whereas the higher values are more common in carbonate rocks. A good average value for K = 70. for which value there is considerable theoretical justification." In order to calculate the resistivity of the connate water R and to estimate its "equivalent salinity" (as NaCl) from an electric log by means of this SP relationship from a knowledge of the static self potential and of the resistiv- ity of the mud filtrate R it is necessary to first correct the resistivity of the mud filtrate measured under surface conditions to the resistivity of this same mud filtrate in the well bore at a different temperature. In order to make this temperature conversion for the mud filtrate the variation of the electrical resistivity of sodium chloride solutions with temperature is commonly used. Since some discrepancies were found in the charts ordinarily used for this purpose, it was felt desirable to make a new study of this relationship based on the published measurement data. Because of the fundamental nature of these relationships and as an aid to other workers in this field, an attempt has been made in this study to show every step in the calculations. CONDUCTIVITY VS MOL CONCENTRATION The most complete published reference on the temperature relationship of sodium chloride solutions of different concentrations is provided in the International Critical Tables.' The basic measurement data on the electrical conductivity of aqueous sodium chloride solutions, at different temperatures, as given in these tables, are reproduced in Table 1. The electrical conductivity values in this Table 1 are expressed as 10' times the specific conductivity k in ohm-'cm'l per unit of concentration in milligram mols per liter of solution C, or: RESISTIVITY VS MOL CONCENTRATION These conductivity values from Table 1 were first converted to the corresponding electrical resistivity values (R) , expressed in ohm-meters, as is conven-

Jan 1, 1953

By N. E. Brown, F. L. Versnyder

THE apparent dependency of the electrical characteristics of hexagonal crystalline selenium on microstructure has aroused much interest in microscopical studies of selenium. Microscopic observations on the crystallization of selenium have been made by Escoffery and Halperin,' P. H. Keck,' and other investigators. It is the purpose of this paper to discuss the microstructural changes observed on polished cross-sections of single layers of selenium after various heat treatments. Observations were also made on crystallization of the free-surface layer of these deposits. In general, all of the transformations studied were either transformations of the vitreous selenium to hexagonal selenium or micro-structural transformation of the hexagonal selenium itself. Procedure The selenium used in this work was obtained from the American Smelting and Refining Co. and was approximately 99.96 pct pure. An intentional impurity of 1 part per 2,000 of bromine was added to the material prior to evaporation. A thickness of approximately 0.002 in. of this selenium was vapor deposited on an aluminum base plate. The maximum plate temperature during the vacuum vapor deposition was 140°C. Mounting of the cross-sectional specimens for metallographic study could not be done in plastic mounting media, as is customary, since temperatures in excess of 50°C would cause unwanted transformations. Consequently, a simple clamp-type device was used to mount the specimens for preparation. All grinding operations were then done carefully by hand in order that the specimen not become heated during this operation. Wet polishing was done on the conventional metallographic polishing laps, using successively finer grinding powders. An extremely careful polish is necessary, since observation and micrography of the specimens are done in the unetched condition under polarized light. The two observations of crystallization made on the free surface of vitreous selenium deposits (Figs. 4 and 5) were made on surfaces which were perpendicular to the cross-sections studied. These free-surface layers were examined directly, i.e., no pre- vious metallographic preparation, as obtained from the vacuum vapor deposition. Microscopic Observations A study was made of polished cross-sections of the vitreous selenium as-deposited. It was noted that in all cases there was columnar crystallization adjacent to the base plate, which appeared to occur during the vacuum deposition process. This observation has also been made by Keck? It also was observed that vagrant spherulitic crystallization occurred in the vitreous selenium. The term "vagrant" is used, since these spherulitic grains appear to crystallize at random throughout the vitreous selenium during the vacuum deposition process. Columnar crystallization at the A1-Se interface and a typical spherulite observed in a polished cross-section of "as-deposited" vitreous selenium may be seen in Fig. 1. Cross-sectional samples of vitreous selenium studied after heat treating individual samples for 20 min in 10" steps from 80" to 220°C revealed that crystallization—in this case, columnar crystal growth —proceeds from the aluminum base plate to the surface of the specimen (Fig. 2). Crystallization was microscopically observed to be complete after the 130°C heat treatment. Visual examination of the free surface of the specimen after the 130 °C heat treatment revealed the readily recognizable grey appearance of the completely crystallized selenium, in corroboration of the microstructural observations. No microstructural transformations then appeared to take place between 130" and 190°C. At 190°C the beginning of recrystallization appeared and proceeded until the columnar grain structure had been completely transformed to equiaxed grains between 210" and 220°C (Fig. 3). Naturally, the grain size of the recrystallized grains at the lower temperatures (190" to 210°C) was smaller than is illustrated in Fig. 3. In addition, polished cross-sections of deposits heat treated at 140°C for 10 min to cause complete crystallization and, subsequently, heat treated in 10" steps from 80" to 220°C for 20 min were studied. As expected, no microstructural transformations took place until the beginning of recrystallization was observed at 190°C. A comparison with the previously studied specimens revealed that recrystallization proceeded almost identically in the two experiments although in the first case the deposits were vitreous prior to the series of heat treatments and in the second case they had been crystallized by a previous heat treatment. By heat treating for longer times (180 min) at lower temperatures, the

Jan 1, 1956

By M. R. Tek

General equations relating the pressure drop necessary to sustain the flow of a fluid through a porous matrix at a given rate have been developed. The results indicate that at high values of flow rate the pressure-flow behavior may not necessarily satisfy the usual Darcy equation. The mathematical analysis, carried through the micro-pore geometry and extended through the macro-reservoir scale, indicate that Darcy's law, of limited applicability to certain ranges of Reynolds numbers, can be generalized through the inclusion of some additional parameters. The "generalized Darcy equation" has also been formulated in dimen-sionless form permitting the evaluation of its predictive accuracy with regard to literature data. A comparison between predicted and experimental values indicates that the generalized Darcy equation predicts the pressure drops with good agreement over all possible ranges of Reynolds numbers. INTRODUCTION The limits and the nature of validity of Darcy's law' has been a subject of every-day interest to the industry for many years. It is well known that as the Reynolds number, characteristic of the fluid flow through porous media, becomes large, Darcy's law gradually loses its predictive accuracy and ultimately becomes completely void. For the last 20 years much has been said and written on this subject. Unfortunately little has been accomplished to bring about a satisfactory agreement, at least on the nature of the threshold of validity of Darcy.'s law. Fluid dynamists, geo-physicists, and engineers all had their individual views, explanations, interpretations and concepts on the subject. To some, a mechanistic analogy with pipe-flow proved a satisfactory explanation.' To others,' turbulence, in its random character, was incompatible with the geometric structure of consolidated porous systems. To some,4 turbulence merely represented a factor influencing the permeability measurements and again to others5,6,7 em-pirical or semi-empirical correlations proved satisfactory from an engineering viewpoint. Deviations from Darcy's law at high flow rates have been studied by systematic experiments by Fancher, Lewis, and Barnes.' In an article on the flow of gases through porous metals, Green and Duwezs conclude that the onset of turbulence within the pores appears unsatisfactory to explain deviations from Darcy's law. This view is held by many others. While the subject remained controversial for many years, the development of vast natural gas reserves throughout recent years further justified considerable interest on this problem from the standpoint of gas reservoir behavior. As large amounts of field data became available from the operation of many gas fields, it became evident that the steady-state behavior of gas wells was not, in general, in agreement or compatible with Darcy's law. This suggested a careful reconsideration of all mechanisms which may account for pressure drops in addition to viscous shear. In a series of articles9,10 . Hou-peurt indicated that deviations from Darcy's law may be explained on the basis of kinetic energy variations and jetting effects without resorting to assumptions on turbulent flow conditions. Another article by Schneebeli11 indicates that special experiments by Lindquist clearly demonstrated that the onset of turbulence does not necessarily coincide with conditions of deviation from Darcy's law. This view is also held by M. King Hubbert.12 Starting with the basic pressure-flow relations suggested by Houpeurt, the derivation, development and extension of analytical expressions to -supplement and generalize Darcy's law has been the objective of this work. MATHEMATICAL ANALYSIS Derivation of Dimensionless Pressure-drop, Flow-rate Relations In considering the flow of a fluid through a porous matrix geometrically represented by a succession of capillary passages in the shape of truncated cones,810 an approximate expression may be derived relating viscous and inertial, i.e., total pressure drop to the physical properties of the fluid, geometric properties of the rock matrix and the rate of flow: ?P/?r = µ/k V [ 1 + c(m4 - 1) p V/16n" mµ w] ..........(1) Let us formally set: c (m4 - 1) / 16n" m = a d ......(2) Such a representation is equivalent to assert that the term [c(m4 — 1)/ 16n"m], variable with various porous media and probably highly variable within a given porous medium, may be macroscopically defined as equal to a lithology factor times the aver-age grain diameter d. In view of the usual grain and pore size distribu-

Jan 1, 1958

By J. C. Fisher

Martensite transformations in steels and other alloys are characterized in part by the absence of composition changes during the growth of a new phase. Transformation occurs rapidly, and there is insufficient time for long range diffusion or partition of alloying elements to take place; martensite reactions in alloys thus are similar to phase transformations in single component systems. A fundamental understanding of martensite transformations in steels is impossible without knowledge of the free energy change upon transforming austenite (face centered cubic iron containing alloying elements) to ferrite (body centered cubic iron containing alloying elements) of the same chemical composition. The present paper assembles the best information available concerning the influence of temperature and composition on this free energy change. Most of the material has been taken from the work of Johansson,' Mehl and Wells,2 Zener3,4 and Smith;5 and indirectly, through these authors, from the work of Austin.6 In agreement with the generally accepted viewpoint, martensite is assumed to be an ordered solution of carbon in ferrite of the same composition as the parent austenite; only at high temperatures and low carbon concentrations is the carbon in ferrite distributed at random. The properties of the disordered solution are estimated by extrapolating the known properties of iron-carbon solid solutions into the range of supersaturation, and the free energy change associated with ordering is estimated from the theory developed by Zener. By incorporating Smith's recent thermodynamic measurements and Zener's theory of ordering, the present analysis modifies previous estimates of the free energy change associ- ated with martensite transformations. Consider a two component system consisting of a solvent A and a solute B. Let Na and Nb represent mol fractions of A and B respectively, let aa = raNa and ab = YbNb represent activities, and let superscripts 1 and 2 refer to phases 1 and 2. The partial molal free energies of A and B in phases 1 and 2 can be summarized as follows: free energy standard state Fa' - Fao1 = RT In an1 pure A' Fa2 - Fa2 = RT In aa2 pure A2 Fb1 - Fbo = RT In ab1 pure B Fs2 - FB2 = RT In aB2 pure B. The free energy of a gram atom of phase 1 is* AF1 = Na'Fa1 + Nb'Fb1 and that of phase 2 is AF2 = NA2FA2 + NB2Fb2. A martensite transformation from phase 1 to phase 2 requires Na1 = Na2 = Na and NB1 = NB2 = Nb, and the free energy change per gram atom accompanying transformation is AFi-2 = NA(Fa2 - Fa1) + Nb(Fb2 - Fb1) = NA[RT In (aA2/aA1) + AFa1?2] + Nb RT In (aB2/aB1) = Na[RT In (ra2/ra1) + AFa1?2] + Nb RT In (TaVTB1). [1] where yn2, yn1, yB2, yB1 are activity coefficients, and where Ma'+* is the free energy change upon transforming a gram atom of pure A from phase 1 to phase 2 at the temperature in question. For martensite transformations in plain carbon steels, A = iron (Fe), B = carbon (C), 1 = austenite (7). 2 = ferrite (a), and Eq 1 is AFr ?a= NFe[RT In (rf.a/rfer) + AFF.r?a] + TVc RT In (eca/rc1)- L2] Nothing is known concerning the values of yFea and yca for carbon concen- , trations in excess of 0.025 pct. However, the approximation rf.7 = 7f." = 1 cannot be appreciably in error for small carbon concentrations, and Eq 2 reduces to Afr-a = NfeFfer?a1 + NC RT In (rca/rcr)- [3] Johanssonl and Zenera have calculated MFfr?a from the specific heat measurements compiled by Austin.6* Their calculated values agree closely, and are summarized in Table 1. The activity coefficients relative to graphite for carbon dissolved in iron vary with temperature according to the relationships d In rcr/d(1/T) = AHcr-R dlnyca/d(l/T) = AHCa/R where AHc? and AHca are the heats of solution of graphite in y and a iron. Assuming the values of AH to be independent of carbon concentration and temperature, In rCr = AHcr/RT + I1 In rca = AHCa/RT + 12

Jan 1, 1950

By R. F. Stewart, A. W. Hall

A method has been developed for continuously measuring the moisture content of coal. The method is based on the thermalization of fast neutrons by hydrogen in the coal. Neutrons from a small radio-isotope source penetrate the coal, are scattered by hydrogen, and measured by a thermal neutron detector. The number of thermal neutrons counted can be directly correlated with the moisture content of coal. In a pilot-scale system, moisture was measured continuously within 0.2% in coal moving at rates up to 20 tph. The method is adaptable in industry for continuously measuring the moisture content of coal at high tonnage flow rates. Such an application would permit continuous recording of moisture in coal without sampling and facilitate quality control. An automatic and continuous method of measuring the moisture content of coal is needed by the coal industry. Automatic control of the coal quality would reduce the cost of coal preparation, improve the product, and thus indirectly increase the use of coal. Moisture in coal can be determined by several methods, but the time required to obtain samples and analyze them by existing methods makes it difficult, if not impossible, to control the quality of the product. Both producers and consumers need a method for continuous and instantaneous measurement of moisture content without sampling in order to regulate process equipment and keep the moisture content of coal within specifications. At the Morgantown, W. Va., Coal Research Center we are developing a nuclear method for continuous measurement of moisture in coal. This method is based on the thermalization of fast neutrons by hydrogen in the water and organic matter of coal. Neutrons from a small radioisotope source penetrate the coal, are scattered by hydrogen, and are measured by a thermal neutron detector. The number of thermal neutrons counted can be directly correlated with the moisture content of coal. Design of a moisture meter based on neutron thermalization depends on many variables, any or all of which can affect the sensitivity of the meter. These factors include those related to the nuclear aspect; type and size of neutron flux and source, type of detecting device, and background count; and those related to the coal being tested: rank, particle size, and ash content. A survey was initiated to eliminate the relatively insignificant factors and to ascertain the magnitude of the major effects. Such information was necessary to fully evaluate the technique and to establish design criteria. Coal contains a relatively large amount of hydrogen in the organic coal substance and the water of hy-dration of the shaly material as well as in the moisture. To apply this concept of moisture measurement to coal requires that the organic substance in coal from any one seam of a particular mine be uniform in hydrogen content. The difference in total hydrogen content of wet and dry coal is relatively small, so that a moisture measurement based on this concept requires a measurement between two large numbers to a high degree of precision. Thus, it was necessary to develop a highly precise instrumentation system for continuous measurement and to obtain a physical arrangement permitting measurement of moving coal with a minimum effect from density variation. EXPERIMENT WITH TRAYS OF COAL Tests were conducted with metal trays containing SO to 100 lbs of coal to develop an instrument system of high precision. A scaling system with a maximum instrument error of 0.2% was used to test different types of thermal neutron detectors. The most suitable type of detector was a boron-10-lined proportional counter tube. While this type of detector showed satisfactory stability, extensive testing disclosed a long-term count reduction probably due to some type of deterioration in the detector. However, development of an electronic system using dual detectors eliminated this deterioration as a serious problem. (The second detector would be used to measure a reference drum of dry coal — the difference in count rate between the wet coal and dry reference coal being a direct measure of moisture content.) Table I, column 1, shows typical results with a 1-curie plutonium-beryllium neutron source and a thermal neutron detector beneath a tray of coal and illustrates the precision of measurement. Consecutive measurements (indicated in Table 1, columns 2-5) of thermal neutrons at various times and positions be-

Jan 1, 1968

By D. D. Smith, D. P. Squier, E. L. Dougherty

A system of differential equations describing the temperature behavior of fluid injected at constant surface temperature in a well is derived and .solved analytically. A formula for the fluid temperature at any time and depth is given, as well us a special formula valid for very large times. These formulas are used to calculate temperatures for several typical cases. The results indicate that, initially, the temperature of the water entering the formation is considerably lower than the injection temperature. This condition lasts for only a short period— less than three days for most cases of practical interest. Following this highly transient period, during which the temperature of the fluid entering the formation builds up to about 50 to 75 per cent of the injection temperature. the system enters a quasi-steady state in which the temperature changes are very slow. After severl years, the bottom-hole temperature will still be 50" to 100°F lower than the injection temperature, hilt the heat losses may he tolerable. INTRODUCTION Predicting the behavior of a hot-water flood requires that the temperature of the water entering the injection interval be estimated. This report describes the development and solution of a system of equations which describes the temperature behavior of the injected water in the wellbore with certain simplifying assumptions. The only previous means known to the authors for describing such a process is that of Moss and White.' Their results appear to be close to those obtained by our method in the practical cases which were compared; this agreement is largely due to the fact that in our method temperature soon approaches a quasi-steady state, as was assumed in their method throughout. However, our model covers all times, is continuous (whereas the Moss-White model depends on breaking the depth into discrete intervals) and. we feel. more closely describes the physical problem. FORMULATION OF THE PROBLEM PHYSICAL SYSTEM AND ASSUMPTIONS The injection procedure consists of pumping water at a fixed surface temperature T., down an infinitely long cylindrical well or tubing of inner radius Any material exterior to the water column such as mud, casing, or cement is regarded as part of the formation. The general behavior of the system may be described qualitatively as follows. When the hot water is first introduced into the system, the temperature difference between the formation and the water is large, resulting in a high rate of heat transfer. As a result, the temperature adjacent to the wellbore rises very quickly. Because the segment of the formation adjacent to the wellbore largely controls the heat transfer rate, the heat transfer rate will become relatively constant when this portion has reached a temperature close to that of the water opposite it. The temperature of the water and formation then increase very slowly with time. The length of the initial highly transient period and the temperature of the water at its conclusion will be functions of depth, injection rate, injection-string radius, surface injection temperature and the physical properties associated with the water-formation system. The following additional assumptions were made. 1. There is no heat transfer by radiation in the system. 2. There is no heat transfer by conduction in the vertical direction in either the injection stream or the formation. 3. The linear volumetric and mass flow rate of the water is constant throughout the injection stream. 4. No horizontal temperature gradient exists in the injection stream. 5. The product of density and heat capacity is constant for both the water and the formation, and the formation thermal conductivity is constant. 6. Initially, both the water in the wellbore and the reservoir are at a temperature given by the (constant) ambient surface temperature plus the product of depth and geothermal gradient (assumed constant). At large distances for the wellbore (r m), the formation will remain at this temperature. 7. The water temperature and the formation temperature at r — r,, are equal for all depths D. DERIVATION OF EQUATIONS The differential equation satisfied by the fluid temperature T,(D, t), which is obtained by writing a heat balance on a cylindrical differential of volume dV of the injection string between the depths D and D i dD, is

By V. G. Leak, R. A. Swalin

The dilhsion of silver and trace concentrations of tin in liquid silver has been rrzeasured in the temperature range from about 975° to 1350°C. The difBsion dala. fil lhe following equations: fov self-diffusion of silver The ratio of DSn to DAg is found to be about 1.34. The higher diffusivity of tin is interpreted in terms of the coullombic repulsion which results from the fact that tin dissolved in silver has a valence of +3 relative to silver. THE phenomenon of diffusion has been well-described theoretically for hard-sphere gases and solids and found to be in good agreement with experimental data for certain gases and solids. Liquid-diffusion phenomena have not been well described theoretically and there is generally a lack of good experimental data. In this investigation self-diffusion and solute diffusion in liquid silver were studied. Silver was chosen as a solvent for two main reasons. First, silver is a noble metal and the atoms are considered to have a spherically symmetric charge field; hence the liquid may be considered to be a random array of approximate hard spheres. Mercury, gallium, and other lower-melting metals were eliminated from consideration since it appears possible that in their liquid states there is some residual long-range order and directional bonding. Second, silver behaves as a monovalent solvent and, while cadmium, indium, tin, and antimony all have nearly the same atomic size, they have chemical valences relative to that of silver of +1, +2, + 3, and +4, respectively. Slifkin, Lazarus, and coworkers1-5 investigated the diffusion of these solutes in solid silver and found that their diffusion rates increased with an increase of the excess valence of the solute. In the solid state the diffusion-rate increase was calculated to be due to a change in local modulus of the solvent caused by the excess valence of the solute.1"3 For the present investigation it was planned to determine the effect of valence upon solute diffusion in liquid silver. It was deduced that a coulombic repulsion between solute and solvent might be responsible for larger volume fluctuations in the vicinity of the solute thereby enhancing the diffusion of the solute atoms. Tin was the first solute investigated and was chosen for experimental convenience. If an excess-valence diffusion effect exists in the liquid state, the solute tin with its excess valence of + 3 might show a large enough effect to distinguish it from the self-diffusion of silver in silver. The silver self-diffusion data were obviously required as a base line for comparison. In addition silver self-diffusion was investigated with a view toward examining the data in connection with the Sutherland- Einstein: Coheen-Turnbull,7 and swalin8 theories of diffusion in liquids. I) EXPERIMENTAL TECHNIQUES The diffusion coefficients for tin and silver in liquid silver were determined in separate experiments using the capillary-reservoir method of Anderson and saddingtono but following closely the experimental techniques outlined by Ma and Swa1in. The radioactive alloy bath was prepared by plating either tin-113 or silver-110 m isotope* onto 99.999 *Isotopes obtained from Oak Ridge National Laboratory. pct Ag rods.* The silver and isotope were melted *Silver obtained from Cominco Co. and mixed in a graphite crucible under a purified argon atmosphere, then outgassed for capillary filling. Some of the fused-silica capillaries were filled individually as reported by Ma and Swalin, but most were filled in a different manner. A long piece of capillary tubing was sealed off on one end and held in the system so that the open end was just above the surface of the molten alloy. The system was evacuated, the open end submerged into the alloy, and argon was admitted into the system up to atmospheric pressure. The molten alloy was forced up the capillary several inches where it solidified and was subsequently cut into segments of the proper length for diffusion annealing. The apparatus for diffusion annealing was the same as that used for capillary filling except that a Pt—Pt, 10 pct Rh therinocouple was placed in the solvent bath in order to accurately measure the temperature during the run. A diagram of the dif-

Jan 1, 1964

By H. Macpherson

Durhm has a well earned reputation for supplying some of the finest coking caals in the world. The caals, in general, vary in rank from 301 to 501/2. Durham has traditionally produced foundry coke for the major proportion of the foundries in Great Britah. Durham coals can be described as clean, soft coals, which yielded, with the old hand methods of coal getting, low ash small coal because the extraneous shale was normally harder than the coal and occurred in larger pieces. Under these conditions, with a plentiful supply of cheap labor, it used to be sufficient, at most collieries, to hand clean the large sizes of coal which could then be remixed with the untreated small coal to produce carbonization coals, ready for the coke ovens, at under 5 pct ash. With the introduction of mechanical methods of coal mining, the coal gradually required more cleaning. The first method adopted to resolve this problem was the introduction of pneumatic dry cleaners for the small coal. Although such machines had little effect on the fine coal (say below 1/8 in.), they could clean the intermediate sizes of coal. This, coupled with hand cleaning the larger sizes above 1-1/2or 2 in., resulted in a combined run-of-mine mixture below 6 pct ash, capable of maintaining the quality and reputation of the cokes produced. In more recent years, the intensification of mechanization and power loading, coupled with gradual exhaustion of the cleaner seams, has created the need for a more complete method of coal cleaning. This particularly applies in the fine sizes (say below 1/50 in.) which normally vary, under present day conditions, between 15 and 35 pct ash and are much too dirty to be included in the raw state in a carbonization mixture. This pronounced change has been accelerated because legislation controlling the dust conditions of mine airs for the prevention of pneumoconiosis has resulted in tk~e extensive use of water underground and a consequent increase in moisture content of the run-of-milie output. The presence of damp fine coal decreast the efficiency of prescreening and dry cleaners, so that this type of preparation for low ash coking coals is decreasing, although it is still used satisfactorily for industrial coals in the medium ash range. Table I shows the gradual increase in mechanization, the reduction in manpower, the increased use of explosives per ton of coal extraction, and the increase in the proportion of coal cleaned by mechanical means in Great Britain. Although similar figures are not available for Durham Div. until after the date of nationalization of the coal industry, it is probable that the increase in mechanical cleaning, particularly by dry cleaners, was more marked in the Durham collieries than elsewhere in the country. As dry clealiers were replaced by coal washeries in the Gritish ccal industry, no special attempts were made to recover the slurry, with the result that large outflows of dirty water were allowed, deposits of slurry came in to lagoons and neighboring streams, and a proportion of fine material was lost from the coking coal. This position, coupled with the higher moisture of the washed coking coal, resulted in adverse effects on coke oven throughputs and coke quality. It is now realized that the natural coal fines are an essential ingredient of coking coals in obtaining the correct coke structure in metallurgical cokes. This, together with economic pressure, led to the introduction of flocculation and filtration plants for the recovery of slurries, and later, when the ash contelits of the filter cakes were too high, to the introduction of froth flotation equipment. After this position had been reached, the tailings from the froth flotation pIants were, in many cases, still allowed to constitute an undesirable effluent. Recent legislation on river pollution has changed this picture; it is now necessary to provide a circuit which is completely closed so far as solids are concerned. The gradual increase in the coal cleaned by wet methods and froth flotation in Durham Div, is shown in Table 11. It is now an accepted feature of new Washeries that. froth flotation should be an integral part of the washing process from the initial installation of the plant.

Jan 1, 1962

By G. Venturello, C. Antonione, G. Della Gatta

Results from work on the effect of inferstitials on recovery and recrystallization of' very pure iron (99.995 pet) doped with nilrogen up to 400 ppm are reported. Nitrided specimens were obtained by heating the iron in a static atmosphere of NH3 + H2. The samples were cold-rolled 80 pet, subjected to a series of isochronal and isothermal anneals, and submitted to examination by X-rays, micrographs, and hardness tests. Small additions of nitrogen show a strong effect in reducing recovery of' the mechanical properties of high-purity iron. At the temperatures of. the experiments, this effect proved greater than in the case of carbon. At 400°C pure iron recovers more than 50 pet of the total hardness increase, carburized iron vecovers 25 pet, and nitrided iron only 10 pet. On the other hand. the addition of nitrogen has, similarly to carbon, a very small effect on recrystallization; the effect is, however, slightly higher than that of carbon. When the concentration Of nitrogen is above the solubility limit in a iron at the temperattue of the experiments, an increase in the frequency of nu -cleation is also observed. THE object of the present work is to improve knowledge on the effect of interstitials both on recovery and on primary recrystallization of pure iron. In fact. at present there are no available data on the effect of nitrogen on high-purity iron. The only work which at present can be somewhat related to this problem is a work of Leak et al.1 in which grain boundary internal friction at high temperature in the presence of increasing amounts of nitrogen is studied by a torsion pendulum. The present work is a continuation of a previous one2 on the effects of carbon. EXPERIMENTAL PART Preparation of the Material. Pure iron was prepared following the same methods used in the pre- vious work2 and was nitrided using controlled quantities of ammonia in an apparatus similar to that used for carburizing. The apparatus consists essentially of a gas-tight quartz tube containing the specimens. The tube, maintained at constant pressure by means of a mercury seal, is placed in a resistance furnace. For nitriding, the NH3 + H2 atmosphere with a suitable concentration of NH3 was introduced into the tube, which had been previously carefully evacuated and degassed by heating at 600°C. The hydrogen used was carefully purified by passing it through a palladium filter. The ammonia required was prepared with the following reaction: CaO + 2NH4CI —CaCl2 + H2O + 2NH3 by heating the mixture of CaO and NH4C1 in a glass flask and then collecting the ammonia in a graduated Hempel burette. For each nitriding program a given amount of NH3 prepared by this method was introduced together with the H2 into the tube previously evacuated. Nitriding of the sample was then performed at 570°C for 48 hr. After this, to ensure a homogeneous distribution of nitrogen, the samples were further heated for 72 hr at 800°C. With this method which uses a static nitriding atmosphere, carefully controlled conditions of purity are obtained. Contrarily, with the conventional continuous-flow methods, using large quantities of circulating gas, there is a greater risk of introducing impurities into the samples. Furthermore, the required nitrogen concentration in the specimen is easily predetermined and obtained. A plot of the relation observed between the initial concentration of NH3 in the gas and the quantity of nitrogen introduced into the iron samples is given in Fig. 1. The data refer to samples of 1.2-mm thickness and to the nitriding conditions previously described. Furthermore, as a comparison, the data relative to two 0.5-mm-thick samples are reported. The presence of a reservoir in the cold zone of the reaction bulb made possible the gradual dissociation of ammonia on the sample in the hot zone. Internal-friction methods were used to determine the content of nitrogen dissolved in the iron samples. Some analyses were also carried out with chemical methods. The following table, Table I, shows a comparison of data obtained with chemical and internal-friction methods. The correspondence between chemical methods and internal-friction

Jan 1, 1964

By R. J. Wasilewski

Electrical resistivity variation with temperature was measured on a series of alloys containting up to 33 at. pct of oxygen over the range 77° to1500°K. The resistivity behavior is highly anomalous and itzconsistent with simple metallic conduction. Both composition and temperature-depended resistivity singularities were observed. A few experiments carried out on Ti-N and Zr-O alloys indicate the presence of similar anomalies. These observations, together with the published data on effects of substi-tutional alloying on the resistiuity of titanium, suggest that the anomalies are inhevent in the electron structure of this group oj metals. The existence of two-band conduction, and a significant shift of bands relative to each other with temperature and/or the electron concentration are suggested. CONSIDERABLE advances have been made in recent years in the alloy theory of simple metals. Very little, however, is known about the bonding in transition metals and their alloys.&apos; Titanium, with its relatively few electrons, may be expected to show simpler alloying behavior than the more complex transition elements. Its alloys with the interstitial elements appear particularly attractive in an investigation of bonding characteristics because of a) the simple nature of the solute elements, b) the remarkable similarity between the equiatomic structures Tic, TiN, and TiO, and c) the extensive solid solubility ranges of oxygen and nitrogen in a titanium reported.2,3 The Ti-O system was chosen for the most extensive investigation because of the relative ease of preparation of suitable specimens. Since the main object of the work was to obtain data on the bonding and its changes on alloying, electron-sensitive properties were primarily investigated. The present work describes the investigation on the electrical resistivity-temperature-oxygen content relationships. A few experiments were also carried out at selected compositions in the Ti-N and Zr-O systems. EXPERIMENTAL Materials and Method. Polycrystalline specimens were prepared in the form of hairpin strips some 50 by 5 by 0.15 to 0.50 mm by direct metal-gas reaction. This was carried out by controlled oxidation followed by a homogenizing anneal at a higher temperature. All the test specimens were fully homogenized as judged from the uniform microstructure and microhardness. To avoid preferred orientation, each strip specimen was annealed in the ß range prior to the oxidation, this procedure assuring random orientation in the strip;4 hence any texture resulting from the oxidation reaction itself affected all the specimens to a similar extent. Titanium used was of high purity (66 DPN, 10 Kg load; major impurities 0,-43G ppm, N,-70 ppm, C-25 ppm, Fe-14G ppm). The solute content of the alloys was determined by weighing, after the reaction with a known amount of oxygen. The specimens in which the discrepancy between the volumetric and gravimetric measurements exceeded 2 pct (or 0.2 mg for the low oxygen alloys) were rejected. The mean between the two measurements was then taken as the oxygen content of the alloy. Check analyses showed no measurable nitrogen contamination. All oxygen contents are given in atomic percent. Zr-O alloys were prepared in identical manner from hafnium-free crystal bar metal, cold-rolled to strip 0.25 mm thick. Ti-N alloys required very long reaction times at the maximum temperature available (1250°C). In order, therefore, to detect possible oxygen contamination, duplicate specimens were reacted in every experimental run, and one of these was analyzed both for oxygen (vacuum fusion) and for nitrogen (Kjeldahl). Only the specimens in which the check analysis showed < 1000 ppm O were then used for resistivity investigation. Since only relatively high nitrogen alloys (7.1 at. pct; i.e., 2 wt pct N,) were investigated, this oxygen contamination was considered permissible. Dc resistance was measured by the four-probe method as previously described.= The temperature was determined with a calibrated thermocouple placed in the center of the specimen hairpin. The errors in the specimen resistance values thus obtained were estimated at 1 pct due almost exclusively to the finite thickness of the potential wires and the consequent uncertainty as regards the true resistance length of the specimen. For the calculation of the specific resistance, however, no dimensional measurements could be carried out on most of the

Jan 1, 1962

Jan 1, 1905

By Lawrence H. Van Vlack, Otto K. Riegger, Gerald I. Madden

The microstructural variations of periclase (MgO) in the presence of oxide liquids are examined under the steelmaking variables of: 1) temperature, 2) liquid composition, and 3) FeO additions under different oxidation levels. Attention is given to the distribution of the phases, both liquid and solid, and to the growth of individual crystalline grains. Silicate liquids penetrate more extensively between individual periclase grains than do liquids containing high percentages of Fe2O3 Higher MgO solubilities in the liquid and lower MgO contents of the solid favor more rapid grain growth. The presence of a second solid phase reduces the periclase grain growth rate and increases the amount of the solid-to-solid contact within the oxide microstructures at high temperatures. The service suitability of a refractory depends on many factors. Two are of major importance and include 1) the thermal resistance to melting, and 2) the mechanical resistance to loads at service temperatures. Neither is a simple consequence of the service temperatures because service conditions will alter compositions, produce partial melting, and induee phase changes. Consequently, the equilibrium phase relationships have been rather thoroughly studied and give a knowledge of the thermal resistance to melting, but do not give full information about the mechanical properties because two refractories with the same types and quantities of phase may have different microstructures. Although variations of microstructures with time, temperature, and composition have been subjects for extensive investigation in metals, only a limited amount of comparable microstructural work has been performed for refractory materials.&apos; This study was an attempt to evaluate some of the consequences of service parameters upon the microstructures of refractories so that bases may be established for the analyzing of high temperature mechanical properties. Periclase (MgO) was chosen as the refractory oxide; variables included those which are encountered under steelmaking conditions such as 1) temperature, 2) liquid composition, and 3) FeO additions under various oxidation levels. Specific attention was given to the distribution of the phases, both liquid and solid, and to the growth of individual crystalline grains. The most closely related work on microstructures of polyphase materials is that of Van Vlack and Rieg-ger2 on the microstructure of magnesiowüstite [(Mg,Fe)O] in the presence of silica. In that work which pertained to solid solutions with less than 40 pct MgO, most of the quantitative work was performed on FeO microstructures. The chief conclusions concerning these relatively low-melting oxide solids were as follows: 1) the rate of crystalline grain growth is inversely proportional to the grain diameter, 2) grain growth proceeds more rapidly at higher temperatures but is slightly retarded by additional liquid content, and 3) a Silicate-containing liquid penetrates as a film between the individual magnesiowüstite grains independent of time, temperature, amount of liquid, or the MgO/ FeO ratio. The above observations are in contrast to prior work3 on the microstructure of silica in the presence of iron oxide-containing liquids where the liquid does not penetrate as a complete film between solid grains. The phase relationships for the compositions of the present work are shown in Fig. 1 which is a summary of the work of several investigators.4 Of importance is the fact that CaO forms a more stable structure with SiO2 and Al2O3 than do either MgO or FeO. The oxygen potential has little effect on periclase unless iron oxide is also present. The iron oxide is ferrous at moderately low oxygen levels, changing to ferric as the Oxygen potential is increased so the spinels, magnetite, and magesioferrite are formed.5 These two phases are relatively stable in air at steelmaking temperatures. I) EXPERIMENTAL PROCEDURE ractory were made with reagent grade Oxides. The magnesium oxide used was 99 pct MgO after ignition, and the iron oxide raw material had a minimum content of 99 pet Fe2O3. The CaO, SiO2, and A12O3 were also reagent grade raw materials. After mixing, the required compositions were pressed into pellets at a minimum pressure of 5000 psi to insure compaction of the raw materials and prevent excess void content. A silicon carbide element tube furnace was used with thermocouple control for sin-

Jan 1, 1963

By Robert B. Fulton

Staurolite, an iron aluminum silicate mineral, is used industrially as a high value-in-use sand-blasting agent, as a premium grade foundry sand, and as the source of aluminum in portland cement manufacture in areas where the aluminum constituent is not economically available from shale or argillaceous limestone. It is produced by E. I. du Pont de Nemours & Co. as a coproduct in titanium mineral production in Florida where it was first recovered on a commercial scale in June 1952 from the Pleistocene sand deposit known as Trail Ridge. In the Trail Ridge deposit it comprises about one-fifth of the heavy minerals, the principal other heavy mineral constituents being ilmenite, leucoxene, rutile, zircon, kyanite, sillimanite, and tourmaline. Staurolite and the other silicate nonconductive heavy minerals are separated from the conductive titanium minerals on high-tension separators. The silicates are then separated from one another magnetically, the staurolite being relatively magnetic. In the total processing, 200 tons of raw sand yield 7 tons of heavy mineral concentrate from which about one ton of staurolite is recovered. This process yields staurolite concentrates of the characteristics given in Table 1. These concentrates are sold as three products with the size distribution of subrounded particles shown in Table 2. All three grades are used in sand-blasting for cleaning metal, for paint removal, and for cleaning buildings. Staurolite compares favorably with lower unit cost abrasives, such as boiler slags and mineral aggregates, in applications where the abrasive is used only one time and is not recovered. Because it is hard, fine, clean, and dense it can reduce blasting time, with less material reportedly being required [ ]

Jan 1, 1983

By G. A. Yuko, J. W. Barton, J. G. Parr

ALTHOUGH previous work1 has shown the compo- sition range of the complex face-centered cubic phase,2 Ti2Ni, to be narrow, no precise limits were established. The purpose of this investigation was to prepare homogeneous alloys on either side of the stoichio-

Jan 1, 1959

By M. Lastra, A. Cruz, J. Menacho

The use of phosphates was studied as a way of purifying acidic copper leach solutions for direct electrowinning. The addition of 2.5 gpl phosphorus to plant solutions originally containing 6.25 gpl Fe (III) at pH 2 0 reduced the iron concentration by one half. Under identical conditions, but without phosphorous additions, the iron concentration was reduced by less than 1 gpl. Any residual phosphorous had no undesirable impact on electrowinning. The concentration ratio of Fe (III) to phosphorous which provides maximum iron elimination was determined. Higher ratios bring about a redissolution of the iron precipitate. Several ways of controlling iron with phosphates are discussed. These take advantages of more rapid and complete iron precipitation at lower pH levels.

Jan 1, 1980

PROF RICHARD ÅKERMAN Stockholm, Sweden DR FRANK DAWSON ADAMS Montreal, Canada PROF RICHARD BECK Friberg, Germany ANDREW CARNEGIR New York, N.Y. DR. JAMES DOUGLAS New York, N.Y. PROF HATON DE LA GOUPILLIERE Paris, France SIR ROBERT A. HADFEILD London, England PROF HANS HOFFER Leoben, Austria HERBERT C. HOOVER Leoben, Austria JAMES FURMAN KEMP New York, N.Y. PROF HENRI LOUIS LE CHATELIER Paris France EZEQUIEL ORDONEZ Mexico City, Mexico DR ROSSITER W, RAYMOND New York, N.Y. PROF RICHARD H, RICHARDS Boston Mass. DR. ING H. C. EMIL SCHROEDTER Dusseldorf, Germany JOHN E. STEAD Middlesborugh, England PROF DIMITRY CONSTANTIN TSCHERNOFF St Petersburg, Russia PROF TSUNASHIRO WADA Tokyo, Japan CHARLES D WALCOT Washingtion D.C.

Jan 1, 1923

The Pennsylvania State College, Mineral Industries Experiment Station, State College, Pa For publications address the Director The Pennsylvania State College through the Minerals Research Experiment Station has issued 10 Bulletins and three Technical Papers, from which the following have been selected as of greatest interest to mining engineers and geologists: Bulletin 1, An investigation of the properties of smitliing coals (1922), free; 2, Petrography of the Mica Pendotite Dike at Dixonville (1926), free; 4, The Helderberg Group from cen¬tral Pennsylvania to southwestern Virginia (1929), 25 cents, 5, Bentonite in Pennsylvania (1929), 10 cents, 6, Production data on Appalachian oil fields (1930), free; 8, Oil field waters of Pennsyl¬vania (1930), free; Technical Paper 2, Condition of water in coals of various ranks.

Jan 1, 1933

By AIME AIME

THE Petroleum Division held a very successful meeting in Los Angeles, Oct. 4 and 5. The meeting was held on the eighth floor of the Chamber of Commerce building, the first day being devoted to technical sessions. Seventy-five members were registered before the opening of the first session. Glenn D. Robertson, vice-chairman of the local section, opened the meeting and introduced Edwin Higgins, managing director of the California Oil and Gas Association, who gave an interesting talk on the recently enacted gas conservation law in California. He explained that the law is an experiment which will be watched with a great deal of interest. The purpose of the law, which went into effect on Sept. 1, is to curb wastage and over-production of gas,

Jan 1, 1929

Nov. 4, 1952, AIME, Morenci Sub-section, Longfellow Inn, Morenci, Ariz. Nov. 5, AIME, Chicago Section, Chicago Bar Assn., Chicago. Nov. 8-8, New Mexico Mining Assn. and International Mining Days, joint convention, Alvarado Hotel, El Paso. Nov. 7, AIME, Pittsburgh Section, National Open Hearth Steel Committee, off-the-record meeting, Hotel William Penn, Pittsburgh. Nov. 7-8, Birmingham Technical Meeting of Southeast Section, AIME, Birmingham. Nov. 10-11, Eighth Annual Meeting of The Magnesium Assn., Hotel Biltmore, New York City. Nov. 12, AIME. Connecticut Section, Hartford, Conn. Nov. 18, AIME, Buffalo Section, National Open Hearth Steel Committee, Hotel Statler. Buffalo. Nov. 19, AIME, Connecticut Section, Hartford, Conn. Nov. 19, American Mining Congress Coal Div. Conference, Wm. Penn Hotel, Pittsburgh.

Jan 1, 1952