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By William B. Senseman

For reasons well known to mining engineers, wet grinding is quite universal in plants having to do with the extraction of metallic values from crude ores. In the processing of the nonmetallic and industrial minerals, dry grinding is the more common method. The crude materials usually contain less moisture than is required for wet grinding and the products usually are marketed in dry form; most of them as powders. To grind wet, therefore, would entail the addition of water and an expense for drying the product, which is not justified. Furthermore, the material would be a dried cake that would still have to be pulverized or disintegrated before use. For producing fine products, air separators have largely replaced the earlier practice of sizing with screens and bolting reels. Mills in which the air-separating feature is an integral part of the design are now commonplace. Mill designs are many and air systems have developed along various lines, but for the purpose of this discussion, only the fundamental idea need be emphasized— the idea of using air for sizing and removing pulverized material from a grinding mill. About 20 years ago, when the use of mills equipped with air separation had become common practice, heated air or gas was introduced to such a system for the removal of moisture. The purpose of this discussion is to outline the developments and trends that have followed this experiment. It is an important development, for mills equipped with air separation are now universally used for pulverizing not only nonmetallic and industrial minerals, but a great variety of other materials. All such mills are essentially the same. Dried material is pulverized, removed by an air stream, trapped in a cyclone collector, and relatively clean air from the cyclone is returned through a fan to the mill. There is no theoretical need for a vent from the system. The practical need is to vent the air that leaks into the system, and, since the cyclone is not 100 per cent efficient as a dust collector, this vented air carries some dust with it. The initial attempt at drying was made on a system like that described, by the addition of a furnace. The minus pressure within the mill draws hot gas from the furnace. Infiltration air, along with the drying gases and evaporated moisture, is vented as before. The first application was made to a mill used for pulverizing coal. The coal contained very little moisture, so very little drying effect was needed for the success of this experiment. Actually, some calculated efficiencies of over 100 per cent were obtained before due allowance was made for the conversion of mill power into useful heat. When moisture is low, the heat obtained from the conversion of mill power is an appreciable part of that required. That drying can be effected in the short time interval available in a grinding mill of this type is better understood by visual-

Jan 1, 1947

By William B. Senseman

For reasons well known to mining engineers, wet grinding is quite universal in plants having to do with the extraction of metallic values from crude ores. In the processing of the nonmetallic and industrial minerals, dry grinding is the more common method. The crude materials usually contain less moisture than is required for wet grinding and the products usually are marketed in dry form; most of them as powders. To grind wet, therefore, would entail the addition of water and an expense for drying the product, which is not justified. Furthermore, the material would be a dried cake that would still have to be pulverized or disintegrated before use. For producing fine products, air separators have largely replaced the earlier practice of sizing with screens and bolting reels. Mills in which the air-separating feature is an integral part of the design are now commonplace. Mill designs are many and air systems have developed along various lines, but for the purpose of this discussion, only the fundamental idea need be emphasized— the idea of using air for sizing and removing pulverized material from a grinding mill. About 20 years ago, when the use of mills equipped with air separation had become common practice, heated air or gas was introduced to such a system for the removal of moisture. The purpose of this discussion is to outline the developments and trends that have followed this experiment. It is an important development, for mills equipped with air separation are now universally used for pulverizing not only nonmetallic and industrial minerals, but a great variety of other materials. All such mills are essentially the same. Dried material is pulverized, removed by an air stream, trapped in a cyclone collector, and relatively clean air from the cyclone is returned through a fan to the mill. There is no theoretical need for a vent from the system. The practical need is to vent the air that leaks into the system, and, since the cyclone is not 100 per cent efficient as a dust collector, this vented air carries some dust with it. The initial attempt at drying was made on a system like that described, by the addition of a furnace. The minus pressure within the mill draws hot gas from the furnace. Infiltration air, along with the drying gases and evaporated moisture, is vented as before. The first application was made to a mill used for pulverizing coal. The coal contained very little moisture, so very little drying effect was needed for the success of this experiment. Actually, some calculated efficiencies of over 100 per cent were obtained before due allowance was made for the conversion of mill power into useful heat. When moisture is low, the heat obtained from the conversion of mill power is an appreciable part of that required. That drying can be effected in the short time interval available in a grinding mill of this type is better understood by visual-

Jan 1, 1947

By AIME AIME

WILBER JUDSON is one of that fairly large group of mining engineers that graduated at an Eastern college, worked his way up in various jobs in the West and in the Latin-American countries, and finally came to New York as an administrative officer of a large mining company. Since coming to New York he has been a loyal friend and counselor of the A.I.M.E., and is now serving a second term as one of its Directors, his first term covering the period 1935-1938. Mr. Judson was born in the capital city of Michigan on July 26, 1880. Probably it was his roving spirit rather than professorial urging that was responsible for the fact that four colleges were responsible for his education: Northwestern, University of Michigan, Harvard (S.B., 1901), and the Michigan College of Mines (graduate study). In his first ten years of professional work he might have been found serving as mine foreman at Catamarca in the Argentine, as superintendent of the Inter Ocean mine at Sunshine, Colo.. as foreman for the Cerro Prieto, Magdalena, Sonora, as superintendent of the Hudson Iron Co. in New York, or as manager of the Dolores mine in Chihuahua for the Mines Co. of America, or in Spain, or in Panama.

Jan 1, 1942

By Zay Jeffries

Rearmament superimposed on buying sprees by the public, caused a general shortage of metals in 1911. and the rare metals were no exception; they also shared with the more common metals the uncertainty of future demand. In general, the apparent undersupply of metals is a favorable condition for the realization of sleeping possibilities of the rare metals, especially if the supply can he made sufficient to take care of the possible new demand. Many changes in metal usage in 1941 were forced because of shortages. When such changes are in the direction of the economic trend there is a speeding up in the tempo of the inevitable change, but when the forced changes are against the economic trend they are likely to be shortlived. In any event, the latter is not a solid foundation on which to build a future business.

Jan 1, 1942

By Willard P. Ward

HAVING been engaged during the past year in the manufacture of ferro-manganese in a blast furnace, I have imagined that some further information on this subject might be of interest to that large number of members of the Institute who are engaged in the iron and steel industries. The great question of the economical production of good steel, ingot metal, or homogeneous iron (we scarcely know now what to call it) from good materials, and at reasonable prices, has, thanks to the intelligence and energy of a few American engineers, been successfully solved in this country. Nearly all first-class railroads, and many that would riot rank so high, have adopted the Bessemer rail. Martin boiler-plates are rapidly gaining ground, in competition with

Jan 1, 1877

By Willard P. Ward

Having been engaged during the past year in the manufacture of ferro-manganese in a blast furnace, I have imagined that some further information on this subject might be of interest to that large number of members of the Institute who are engaged in the iron and steel industries. The great question of the economical production of good steel, ingot metal, or homogeneous iron (we scarcely know now what to call it) from good materials, and at reasonable prices, has, thanks to the intelligence and energy of a few American engineers, been successfully solved in this country. Nearly all first-class railroads, and many that would not rank so high, have adopted the Bessemer rail. Martin boiler-plates are rapidly gaining ground, in competition with

By L. C. Graton

Although marked by numerous well-known attributes of its own, gold does not possess a kind and range of physical, chemical and geological characteristics wholly different and apart from those of other metals. Instead, it is merely one of the family of metals, with its individual and distinctive traits subordinate to the underlying family relationships and resemblances. The geologist concerned with pure science will pursue, therefore, the same general course and will examine the same broad kinds of facts and interrelations when studying the occurrence of gold as when studying that of copper or cadmium, or any other metal. But when we come to consider the use and economics of the metals, we discover that gold differs strikingly from all the others. Gold, in short, is unique, not by virtue of its inherent characteristics, but because of a peculiar and concerted psychological regard in which it is held. It will be evident, therefore, that the geologist who would deal with gold supply must give far greater weight to economic considerations than is required in his contacts with any other metal. If the geologist be called the scientist of occurrence, and the economist the scientist of use, the economic geologist stands as the necessary link between them. Perhaps it is in part because the economic geologist has made himself more familiar with the science of occurrence than with the science of use and has thus in some degree failed to bridge effectively the gap between the two fields, especially with regard to gold, that the usen1 of gold now appear to be in a state of general concern and even of alarm for the security and adequacy of future supplies. In the case of no other mineral commodity do the users, as a rule, trouble themselves greatly about the adequacy of supply except in so far as that may affect the price which they shall have to pay for the commodity. Oversupply, with resulting low price, they regard as a gift of good fortune. As to long-term undersupply, they are generally content to go ahead on faith, leaving the producer to discover as best he may the means for meeting their requirements or the inventor to find a substitute. But history has shown that for gold a different situation exists. While

Jan 1, 1931

By J. C. Motz

Introduction The variations in crushing plant design seen during the past 30 years provide a valuable source of information and experience from which one can select the optimum arrangement for a specific requirement. The purpose of this paper is to examine some specific equipment configurations as they relate to operating efficiency, plant availability and final product size in the form of mill feed. Due to the varied ore properties, physical space limitations, size of ore body and financial resources, there is no single crushing or grinding flowsheet that is best. Since energy costs have risen dramatically during the recent past, it became obvious that significant savings are possible by selecting equipment and a circuit which offers low power requirements balanced with low wear metal and installed equipment costs. Relatively clear and measurable are the metal and maintenance costs and the ever increasing cost of energy. Metal costs in the form of crusher liners have not quite doubled in the last 20 years, while power costs have increased by a factor of four or five, depending on the region considered. Estimates made only a few years ago on the increased cost of energy are obsolete in view of the recent unstable conditions. Since power is therefore becoming the largest cost area, it behooves us to investigate potential cost saving methods in the form of lowering the KWH/Ton of crude. Crushing To reduce run-of-mine to mill feed requires reduction in a series of stages. The physical size and power requirements of a crusher capable of reducing hard rock vary depending on the application. Extended experience in most crushing plants show that a minus 19MM (3/4 in.) rod mill feed can be and is being produced in three stages of crushing. In the majority of cases, the last crushing stage is closed circuited using anywhere from 19MM (3/4 in.) to 14MM (9/16 in.) slotted openings on the sizing deck. In some copper concentrators, the mill feed is all passing 13MM (1/2 in.) using three stages of crushing and 14MM (9/16 in.) square openings on the closed circuit screens. It was felt by some that crushing to this fine size is only possible if the ore is friable and is relatively soft in comparison to the harder ores. Our results show that some of the copper ores are as hard as taconite and are crush-

Jan 1, 1982

T. Kirke Rose, London, Eng. (communication to the Secretary*) :—The authors have shown that, under certain conditions, the rate of dissolution of gold by chlorine and bromine is reduced by the addition of 10 per cent. of silver to the gold, and that the action is almost stopped when the silver amounts to 30 or 40 per cent. of the alloy. Even if full recognition is given to the practical way in which the work was done, however, it is to be regretted that Prof. Hofman and Mr. Magnusou did not determine the temperature at which the experiments were carried out. From the details given, it may be inferred that the temperature was raised by chemical action by about 20' C. when 21 g. of sulphuric acid was added, and that the mixture was then slowly cooled down during the experiment. When bromine or very weak chlorine solutions were used, there could not have been any perceptible heating-action. As the action of both chlorine and bromine is aided by heat, it follows that the stronger solutions of chlorine were given an unfair advantage over the weaker solutions, and over bromine. If the temperature had been the same in each case, I do not think that the conclusions deduced by Prof. Hofman and Mr. Magnuson' would have been found to be justified. (This is speaking generally. In barrel-treatment the conditions are similar to those in the experiments.) The superior speed of bromine as compared with chlorine at equivalent strengths is not yet disproved, and the differences noted between strong and weak solutions of chlorine may have been largely a function of the temperature. Moreover, the authors used somewhat-coarse particles of gold, and did not try how far time was a factor, although it is obvi-

Jan 1, 1906

By J. A. Eisele, D. J. Bauer, L. E. Schultze

Approximately 100 million mt of magnetic reject tailings, which contain apatite and about 1% yttrium and rare-earth elements, exist in the eastern U.S. as a result of iron ore mining operations. At the present time, no economic process is available for recovering yttrium from this material. The U.S. Bureau of Mines (USBM) studied the problem to determine if an effective low-cost method could be found, thereby increasing our domestic yttrium reserves. [Fig. 1] is a line drawing of a photograph taken during microprobe analysis of a sample of the tailings, and shows the distribution of yttrium. Typical analysis of this material is 0.14% yttrium and 1.1% rare-earth elements (mainly lanthanum through neodymium). Over half of the yttrium is present as a hydrated Ca-Y silicate deposited along interfaces in the grain structure; whereas, the remainder of the rare-earth elements occur as Ca-Fe-RE silicates. The remaining yttrium and rare-earth elements are in solid solution with the

Jan 1, 1977

By J. L. Martin, W. M. Campbell

A new electric logging method, called displacement logging, often gives a direct indication of the presence of mobile hydrocarbons in hydrocarbon-bearing formations. This method is based on the detection of a bank of connate water which is formed between the invading mud filtrate and virgin formation fluids in these cases. The existence of this phenomenon has beer, verified by laboratory studies and by actual field logs taken in known oil sands. INTRODUCTION During the past decade increasing use has been made of conventional electric logs to determine the amount of oil or gas in formations traversed by a borehole. This determination requires knowledge of several factors, such as true resistivity of the formation, formation factor, and water resistivity. Sometimes all of the factors necessary to make a reliable saturation calculation are not available. Also, the computations and corrections which are necessary in such a study often require the services of an experienced log analyst. It has long been the desire of exploration people to have a logging device which will locate hydrocarbon-bearing formations directly without requiring complex interpretation methods. The displacement log, while not completely fulfilling this desire, appears to be a Step in that direction. Basis for the Device The basis for this device stems from a phenomenon which occurs when mud filtrate invades a formation which contains displaceable hydrocarbons. As the mud filtrate invades the formation, most of the oil or gas is pushed out of the invaded zone, leaving residual oil. However, in addition to displacing most of the oil or gas, the connate water is also swept out, since the originally irreducible water is mobile in the presence of a water phase.1,2,3 Tonsequently, this irreducible water piles up as a bank between the virgin oil zone and the invading filtrate. If the mud filtrate is of higher resistivity than the formation water— as is commonly the case—the resulting annular zone, containing the bank of formation water, will be of lower resistivity than either the virgin oil-bearing formation resistivity or the invaded zone resistivity. This resistivity configuration, going from high to low to high again as the distance from the borehole increases, is found only in those zones which contain displaceable hydrocarbons. A device which would reliably detect this low resistivity zone would give a direct indication of mobile hydrocarbons. Illustrations This phenomenon is illustrated in Fig. 1 and 2. Fig. 1 shows a sketch of a zone containing salty connate water plus displaceable hydrocarbons, along with graphs showing fluid content and electrical resistivity vs distance from the borehole, before invasion occurs. Fig. 2 shows this zone, together with fluid content and resistivity graphs. after invasion by a fresh water mud. The resistivity pattern on moving away from the borehole is high: low: high. The absence of the low zone phenomenon in water zones is illustrated in Fig. 3 and 4. Fig. 3 shows a sketch of a zone containing salty formation water and residual oil, along with graphs showing fluid content and electrical resistivity vs distance from the borehole, before invasion occurs. Fig. 4 shows this water zone, together with fluid content and resistivity graphs, after invasion bv a fresh water mud. In this case the resistivity pattern on moving away from the borehole is high: low since there is no change in water saturation at the head ol

Jan 1, 1956

By AIME AIME

THAT neither the Reconstruction Finance Corp. nor its subsidiary, the Metals Reserve Corp., are in competition with private enterprise was stressed by Charles B. Henderson in an informal talk before the N. Y. Section, A.I.M.E., on Sept. 23. Among other things, the speaker stated that the R.F.C., since its establishment, had authorized loans of $12,000,000, of which over $8,775,000 has actually been distributed. Of this amount, over $6,600,000 has been repaid. None of this money was appropriated by Congress, the sole assistance from that body being the initial authorization of $500,000,000 capital stock.

Jan 1, 1941

By Rossiter W. Raymond

(Read at the Amenia Meeting, October, 1877.) IN the case of The Eureka Consolidated Mining Company v. The Richmond Mining Company of Nevada, recently tried at San Francisco, California, the real defendant was the Richmond Consolidated Mining Company, of London; but this being a foreign corporation, holds its mining property in Nevada through the Nevada corporation of similar name, in which the London Company owns all the stock, except the few shares necessary to "qualify" the American directors. The trial would naturally have taken place in the Circuit Court at Carson City, Nevada, and before a jury. But by stipulation of the parties, the case was tried in San Francisco, before Hon. Stephen J. Field, Justice of the Supreme Court of the United States, Hon. Lorenzo Sawyer, United States Circuit Judge of the Ninth Circuit, and Hon. E. W. Hillyer, United States District Judge, for the District of Nevada. The hearing began July 23d, 1877. The witnesses occupied two weeks, and the argument of. counsel three days. Very eminent lawyers were. engaged on both sides ; for the plaintiff, Messrs. Solomon Heydenfeldt, R. S. Mesick, John Garber, and H. J. Thornton ; for the defendant, Messrs. S. M. Wilson, Thomas Wren, and J. J. Williams. The court held the case under advisement until August 22d, when Mr. Justice Field delivered its unanimous opinion in favor of the plaintiff. The action was a complaint in ejectment, and an appeal was taken to the United States Supreme Court. The questions at issue between the Eureka and the Richmond Company in this suit, comprised several points in the construction of the mining law of the United States, and its relation to the customs and regulations of the mining districts, which possess an importance and an applicability far beyond the limits of the case in which they arose. It is my purpose to state these points, the arguments

Jan 1, 1878

By N. A. Zeigler

The present publication is a continuation of the work on gas analysis described in a paper presented before the Institute of Metals Division year ago.' While that paper was largely descriptive in character dealing with the various parts of the apparatus and method of operations the present one gives numerical data obtained as a result of a series c experiments with iron-carbon alloys. The apparatus and the method applied are essentially the same as previously described, changes bein only in minor details. Attention should be called to the fact that in the present work we ar dealing with the gaseous mixtures obtained as a result of vacuum meltin of various ferrous alloys. It should be understood that when the term "degasified sample" and "products of degasification" are used, the refer to the sample remaining after the vacuum fusion of the alloy an the gaseous products removed therefrom, respectively. The write does not wish to create the impression that the metallic products of thj process are absolutely free from any gaseous elements, nor that the gase obtained are present as such in the original sample. These two point are not yet definitely known and are subjects for future investigatior The point, however, which has been established beyond doubt, i that all the gases dealt with come from the metallic charge and ar present either in the charge as such, or are produced as a result of chemic: reactions going on within the charge. The suggestion that the gases an due to the reactions between the metallic charge and the refractor materials has no valid basis. General Procedure A series of iron-carbon alloys was prepared in a magnesia-line graphite crucible placed in a high frequency laboratory furnace open t the atmosphere. The materials used were Westinghouse electrolyti iron and Acheson graphite. Each alloy, after it was completely molter was kept in the liquid state for 10 min., cast into a small iron mold, an

Jan 1, 1929

George IV. Goetz, Milwaukee, Wis.: Mr. Campbell deserves much credit for his interesting paper. The literature of the development of the open-hearth process is distributed in many technical journals, and is difficult of access to many engineers. Since the development of the basic process, the open-hearth furnace has been raised from a subsidiary to an independent position. Certain high grades of soft steel can be produced in the basic open-hearth furnace, which cannot be produced by any other known process. In the United States the charges for the acid process generally consist of either scrap and pig-iron or so-called wash-metal and scrap : the pig-and-ore process, as carried out in England, is practiced but very little. The introduction of the basic process has made it possible to use about four times as much pig-iron with scrap as can be used in the acid mixtures. The availability of a cheap pig-iron, very low in silicon and sulphur, and carrying several per cent. of manganese, is one of the reasons why the basic open-hearth process has developed so rapidly in Germany, as regards the output per furnace and the excellent quality of the material produced. The acid Bessemer steel has an inherent stiffness, which is plainly shown when spring steel is made by the Bessemer and by the openhearth processes. In order to get them of about equal stiffness, the open-hearth steel must have about 0.60 per cent. carbon ; whereas, the Bessemer steel must then have ahout 0.45 carbon, the remaining constituents being apparently about the same in each product. It has proved impracticable, with American coke-pig-iron, to interrupt blowing at a certain point in order to make hard steel; and experience has therefore shown that it is best to eliminate nearly all the carbon, and then to recarburize to the desired point. This practice

Jan 1, 1894

By L. A. Schrider, J. A. Wasson

A method of predicting waterflood performance has been developed that combines certain facets of several previously published prediction techniques. The manner of combination has required the development and use of some new and some little-known relationships and has eliminated several of the weaker assumptions inherent in the original individual prediction methods. This approach, which was designed for computer solution, has removed the necessity of referring to plotted curves and permits the analytical prediction of water flood performance for a five-spot well pattern in either homogeneous or stratified reservoirs. The Predicted values are expressed in common oilfield units rather than in abstract or dimensionless terms. The calculation procedure has been programmed in FORTRAN IV and the entire program listing is available to potential users.* Introduction Prior to initiation of secondary recovery of oil by waterflooding, the possibilities of economic success or failure must be evaluated with the greatest practical accuracy. Although many prediction techniques are available, most, if not all, have serious limitations. In recent years, the Bureau of Mines has attempted to stimulate interest in the secondary recovery of oil from Appalachian pressure-depleted reservoirs. Waterflooding, because of its widespread acceptance and success, is the principal secondary-recovery method considered. During the life of the project, several performance prediction methods have been studied and applied. Because these methods, individually, have inherent assumptions and limi-tations, portions of some of them have been selected and combined in an effort to eliminate such shortcomings wherever possible. We believe that the resulting technique is as accurate as the necessary available data will permit and that it has several distinct advantages over previously published methods. Development of the Method The fractional flow equation developed by Buckley and Leverett' from Darcy's law is the fundamental mathematical statement describing immiscible fluid-fluid displacement in porous media. A generalized form of this relationship, whose derivation is readily available in the literature, is The formation dip, a, is usually very small in those petroleum reservoirs being considered for pattern waterflooding in the Appalachian area. Therefore. in many cases. a has an almist negligible value. In addition, Ap, the difference between the density of water and the density of oil, is relatively small. For these reasons the gravitational term may often be neglected. Capillary pressure is a function of saturation, which is in turn a function of distance from the upstream boundary of the system or the injection well. In this study it is assumed that the frontal zone of the waterflooding (or zone of capillarity) has negligible length and that only those saturations in the water-swept zone at breakthrough and later are of interest. As the distance in a waterflood pattern is comparatively large and the change in water saturation with distance is usually small, the change in capillary pressure with distance is negligible. The simplified form of the fractional flow equation is appropriate, therefore, in this application. Three variables must be considered in determining that fraction of the total fluid flow that consists of water: the viscosity ratio, saturation, and relative permeability ratio.

Jan 1, 1969

Discussion of the paper of Ernest Stütz, presented at the New York Meeting, October, 1913, and printed in Bulletin No. 79, July, 1913, pp. 1257 to 1265. H. 0. HOFMAN, Boston, Mass.:-I have hunted in vain for a figure which gives a dehydration temperature of cement. I was wondering if Mr. Stütz had a figure of that kind. E. STÜTZ :-No, I am afraid I have not. H. 0. HOFMAN :-I believe some figures have been published that cement disintegrates at 400° or 500° C. It seems tome a very low temperature. Mr. Stütz just made the statement that the disintegration of this briquette begins at the temperature at which the briquette begins to sinter. E. STÜTZ :-Above the sintering point. H. 0. HOFMAN :-The sintering point would be about 1,200° C. E. STÜTZ :-Yes, roughly speaking. I am afraid I have no information about the exact degree of dehydration. H. O. HOFMAN :-I have looked a great deal for such a figure and I have not been able to obtain it. Professor Howe says I might have tried myself. But my interests were directed in another line; although-that is, perhaps, a good suggestion. CHAIRMAN RICHARDS:-Is not Portland cement sometimes used for the test in a cupellation furnace and a drying-out furnace ? H. O. HOFMAN :-Yes, it is used, but that is a higher temperature, of course. But I have been trying to get a figure as to where it loses all its water. I understand it begins to lose water at 500° C. But there are different silicates or hydrosilicates in the cement, so that one would have four or five or sit figures to show the different stages at which the cement loses its water. CHAIRMAN RICHARDS :-I would ask whether the use of this material in blast furnaces has shown increased capacity of furnace or decreased consumption of fuel.

Jan 12, 1913

By D. E. Thomas, C. E. Birchenall

ALTHOUGH Eoltzmann gave a mathematical solution for the diffusion equation (for planar diffusion in infinite 01. semi-infinite systems only) in 1894 allowing for variation of the diffusion coefficient with a change in concentration, it was not until 1933 that this solution was applied to an experimentally investigated metallic system. The calculation was carried out by Matano' on the data obtained by Grube and Jedele3 for the Cu-Ni system. Since that time concentration dependence of the diffusion coefficient has been demonstrated for many pairs of metals. However, the nature of this dependence has never been fully elucidated. Many investigators have suspected that these variations could be related to the thermodynamic properties of the solutions, one of the earliest explicit statements being contained in a discussion of irreversible transport processes by Onsager' in 1931. Development along these lines has been greatly retarded by the lack of reliable data on the variation of tliffusivity with concentration, the paucity of the thermodynamic data for the same systems at the same temperatures and compositions, and an incomplete understanding of the relation of the thermodynamic properties of the activated state for diffusion to the bulk thermodynamic properties. The last factor has been discussed by Fisher, Hollomon, and Turnbull.5 In many instances where data exist, it is difficult to know which are acceptable. This problem probably applies more strongly to diffusion data than to activity measurements. For instance, four sets of observers"-" have reported self-diffusion coefficients for copper. The average spread between extreme results is a factor of about four, though the individual sets of data are self-consistent to about 20 pct. Thus one or more factors are out of control, at least in these experiments, making estimates of internal error unreliable. The most reliable diffusion data in most systems have resulted from the use of welded couples with a plane interface from which layers for analysis are machined parallel to the interface after diffusion. The layers are analyzed, and the result is a graphical relation between distance and concentration, usually called the penetration curve. Given the same set of analytical data and distances and following the same procedure in computation, different observers will generally produce diffusion coefficients which vary appreciably, especially at the extremes of the concentration range. Experiments must be carefully designed so that the precision is good enough to answer a particular question unequivocally. In the first calculation of the dependence of the diffusion coefficient on concentration in the metallic solid solution Cu-Ni, Matano found that the coefficient was insensitive to concentration from 0 to 70 pct Cu, after which it rose more and more steeply to some undetermined value as pure copper was approached.' The same behavior was reported for Au-Ni, Au-Pd, and Au-Pt.* The data used were those of Grube and Jedele which were very good at the time, but are not considered particularly good by present standards. Furthermore, the method of calculation makes the ends of the diffusion coefficient-concentration curve unreliable. For better reliability, the high copper end of the curve has been checked by incremental couples, where the concentration spread is 67.7 to 100 atomic pct Cu. The implication of the curves calculated by Matano was that diffusion is very concentration sensitive in one dilute range of this completely isomorphous system and hardly at all in the other. Matano's result is confirmed. Later Wells and Mehll0 published data on diffusion in Fe-Ni at 1300°C, which represent a thorough test of the shape of the concentration dependence curve. They ran couples with the following ranges of nickel concentration: 0-25 pct, 1.9-20.1 pct, 0-20.1 pct, 20.1-41.8 pct, 0-99.4 pct, and 79.3-99.4 pct. Although the trend of the data indicates an S-shaped concentration dependence, their curve was drawn to the pattern set by Matano. Their original data have been recalculated for the 0-99.4 and 79.3-99.4 pct couples. Wells and Mehl's points and two independent recalculations from the raw data are plotted in Fig. 1. What appears to be the best curve is drawn through them. This curve shows little sensitivity to composition in both dilute ranges with a strong dependence at intermediate composi-tions.? Similar experiments on the Cu-Pd system are reported here at temperatures where solubility is unlimited. These lead to the same type of concentration dependence for the diffusion coefficients as was found upon recalculation of the data for the Fe-Ni system. Experimental Procedure Cu-Pd: The concentration dependence of the diffusion coefficient may be determined by the use of

Jan 1, 1953

By M. J. McPherson

Having worked on the thermodynamics of air/liquid-water mixtures passing through the surface fans of deep mines, I find this paper of great interest and congratulate the authors on producing it. There are two matters, however, deserving discussion. First, the authors have described the classical theory of fog formation with fogging occurring at "supersaturation." In fact, the process of fog formation begins well below 100% humidity. The more strongly hygroscopic nuclei in the atmosphere will attract water molecules and begin to grow at a relative humidity perhaps as low as 70%. The process is a dynamic one with both condensation and evaporation taking place throughout the mixture on microscopic liquid surfaces. As saturation is approached, the rate of condensation accelerates rapidly producing the familiar reduction in visibility. Hygroscopic nuclei are present in all natural atmospheres and under the appropriate conditions of pressure and temperature, will produce clean fogs. However, if the air is polluted by particulates from combustion or other processes then the resultant coagulation with growing liquid particles may produce dense (and sometimes photochemical) smogs. It is this process that is likely to occur in underground mines when moist air is cooled below dew point. Second, the authors have summarized very well the individual measures that might alleviate the problem. In particular, I agree that neither heating nor refrigerating the air, by themselves, provides a satisfactory solution. However, there is a combination of these that provides a neat and effective control of fog formation. This involves a small, self-contained refrigeration unit within a duct but without the usual external heat rejection facility. The air is cooled below dew point and, hence, dehumidified on passing over the cold evaporator coils. The heat from the condenser is rejected back into the air down-stream from the water eliminator, as shown in [Fig. 1]. The duct configuration can be designed to create good mixing at the outlet.

Jan 1, 1984

By Peter Greenfield, Paul A. Beck

Thirty binary systems of vanadium and chromium group transition elements with second and third long period transition elements were explored in regard to the intermediate phases formed. It was found that the phases predominating in these systems are s, AB type with ordered a-tungsten or C8 structure, close-packed-hexagonal with small unit cell dimensions and, finally, phases isomorphous with 1-manganese. IN recent years, considerable information has become available concerning the intermediate phases in binary systems of the transition elements. Thus, the s phase has been found to occur in most of the binary systems of vanadium, chromium, and molybdenum with the group of elements manganese, iron, cobalt, and nickel.' It was observed that, while the rr phases formed by chromium with manganese, iron, or cobalt possess a considerable temperature range of stability, particularly in the Cr-Co system, the corresponding s phases with molybdenum are limited to a temperature range of less than 400" above about 1200°C. Goldschmidt' reported v phases of tungsten with iron and cobalt, and these are apparently stable only at (and above?) 1400°C." Exploratory work in this laboratory with Fe-W and Co-W alloys of approximately 60 atomic pct W annealed at 1300°C did not produce X-ray patterns suggesting the presence of a phase. It appears then that the phases of iron and cobalt with the chromium group elements decrease in stability as the two components are chosen from long periods further removed from each other. From the available information, it might be concluded that the controlling factor is the increasing difference in atomic radii between the components. In contrast to the a phase, the phases formed by iron and cobalt with chromium group elements' are stable only when the latter have large atomic radii (molybdenum and tungsten); the corresponding phases with chromium do not occur. When the difference in atomic size becomes still larger (r,/r,, approaching the ideal value of 1.225), the u and p phases are replaced by Laves phases (AB,), as in the alloys of iron and cobalt with columbium," tantalum." and titanium."-" However, atomic size certainly cannot be the sole determining factor, since, for instance, in contrast to the very stable (Mo, Co)p phase, no such phase occurs in the Mo-Ni system even though the atomic diameters of cobalt and nickel are nearly the same. Similarly, chromium and cobalt form a a phase in a wide temperature range," but the corresponding s phase in the Cr-Ni system is missing. It has been shown that the composition of the u phase in various binary and ternary systems of transition elements in the first long period may be correlated in a fairly quantitative manner with the number of electron vacancies. The influence of electronic structure is probably present also in binary and ternary phases' and to some extent, apparently, even in Laves phases." " Although the absence of phases in the Cr-Ni and Mo-Ni systems has not as yet been explained on the basis of electronic structure, it appears reasonable to suspect a connection. One of the great difficulties in arriving at well founded rules in regard to the alloying behavior of transition elements lies in the lack of reliable information concerning the details of their electronic structure in the metallic and alloy form. The theoretical penetration of this field appears to be beset by very considerable difficulties, even when the complications due to alloy formation are disregarded. Another great source of uncertainty is the scarcity of phase diagram information even for binary systems of the transition elements so that only a very limited basis is provided for generalizations as to the occurrence of intermediate phases. For instance, very few binary phase diagrams of second and third long period transition element systems have so far been published. The present work was undertaken in order to survey the various types of intermediate phases occurring in 30 binary systems of elements of the group vanadium, columbium, tantalum, chromium, molybdenum, and tungsten with the elements rhenium, ruthenium, rhodium, palladium, and platinum. For most of these binary systems phase diagrams are very incompletely or not at all known, as will be further reviewed.*

Jan 1, 1957