Search Documents

By T. Egleston

I HAVE to announce with great regret that our distinguished honorary member, Louis Gruner, died in Paris in March last. The Institute, in his death, has lost one of the first as well as one of the greatest of its honorary members. I speak with great feeling, as he was both my instructor and my friend ; and I am sure that if he could hear what I am about to say of him, lie would object to it. Mr. Gruner's modesty was such as even to prevent, except in his own Corps, the thorough appreciation of his work in his own country. I think be mas better appreciated by those who are familiar with his labor in almost any other country than his own. A just man, a thorough scholar, a great investigator, he was so unselfish that almost the last act of his life, and the last letter he signed, only a few hours before his death, had for its ohject to render a service to one of his former pupils. I think no one who mas ever associated with him could forget, in the greatness of his learning, the sincere and earnest friend, mho was always ready to render a service, where such service could be rendered even at great inconvenience to limself. His own motto, "Sein, nieht schein;" that is, "Be, not appear to be," was singularly descriptive of his character; and, what is more than all, he was one of the most earnest Christian men with whom it has ever been mv. good fortune to be thrown in contact. There are few such men. He was one of the greatest metallurgists that Europe has ever produced; a man the more remarkable because, though known to most of us as a metallnrgist, some of the best work of his life was in the domain of geology to which he contributed very important researches and memoirs, which will remain permanently among the valuable additions to the geology of his own country. He was, at the same time that he was the greatest metallurgist in Europe, a brilliant chemist, a thorough geologist, a distinguished professor, and an expert, practical miner, whose advice and methods had only only to be known to be followed. Mr. Gruner was born in Smitzerland in 1809, and graduated from the Polytechnic School of Paris in 1530 and entered the School of Mines, from which he graduated with distinction in the Corps of Government Engineers of Mines at an early age, and was immedi-

Jan 1, 1884

By J. E. Hove

The high temperature physical properties of graphite are reviewed and interpreted in the light of present day knowledge of the mechanisms affecting these properties. The thermal and mechanical behaviors only are discussed and, whenever possible, comparisons are made with other refractory materials. Possible further studies are indicated, including some carbide work. AS long as the term high temperature implied only temperatures up to about 1000°C, the materials problems which arose could usually be handled by fairly conventional metal alloy types, such as the Co-Cr-Ni superalloys, for which there exists a great deal of technology. Perhaps this temperature can still be considered an upper limit for normal applications, but it is certainly true that the number of abnormal applications is increasing rapidly. The advent, in recent years, of ram-jet and rocket missiles and of high power nuclear reactor heat sources has raised a host of questions concerning the basic problem of what material to use in the temperature range up to 2000°C and higher. While there are, of course, many metals, in the second and third transition series, which melt at considerably higher temperatures than this, these metals are, at present, pretty well excluded from practical use by other considerations, such as re-crystallization, chemical activity, or excessive plastic deformation. The behavior of metals, from the standpoint of dislocation theory, is just beginning to be understood and thus there is some hope for the future development of very high temperature metals, but the immediate problems would most logically appear to have solutions involving the nonmetals, such as the refractory ceramics and graphite. For this reason, there is presently a great deal of engineering and experimental research being performed on the latter materials, much of this research being exploratory in the sense of gathering new property data. The situation, so far as graphite is concerned, is somewhat more fortunate than with the other refractory solids in the sense that a great deal is already known about its basic properties. This stems both from the fact that the carbon-carbon bond has been of interest to chemists for a long time (and graphite can be considered as a very large aromatic molecule, if desired) and the fact that its properties, both as a function of temperature and of radiation damage, are of critical importance to nuclear reactor designers. It is still true, of course, that such fundamental questions as why graphite remains solid to such a high temperature and why it has such a high thermal conductivity cannot entirely be answered at the present time. It is, nonetheless, meaningful and instructive to consider such problems in the light of existing knowledge. This is what the present paper will attempt to do. Before going on, it may be appropriate to classify graphite and justify its discussion before readers primarily interested in metals. Graphite is comparatively unique among materials in that there is always a property or group of properties which precludes calling it either a metal, a semiconductor, or a ceramic. It has the high electrical and thermal conductivities of a metal, but the artificial, poly-crystalline types show a negative thermal coefficient of electrical resistivity, generally characteristic of semiconductors. On the other hand, semiconductors, by definition, show an ever increasing resistivity as the temperature is lowered, whereas graphite approaches a finite, and, indeed, a rather low resistivity in the region of 10°K and, furthermore, a good single crystal of graphite has a positive temperature coefficient, as for a metal.' On still another hand, its porosity and brittleness at lower temperatures would put graphite in the ceramic class although, unlike most ceramics, it is readily machinable and has a high resistance to thermal shock. All things considered, it is probably more nearly appropriate to call graphite a metal than anything else. Although certainly outstanding in some ways, graphite has its peculiarities and, especially if the reader is unfamiliar with the data, it is probably valuable to review some representative property variations at high temperature. This review is meant to be mainly illustrative and no attempt has been made to be exhaustive. Review of High Temperature Properties At ordinary pressures, graphite does not melt, but sublimes directly into the gaseous phase at about 3700°C. Although the phase equilibrium diagram is still in some doubt, graphite will melt, at a slightly higher temperature, at pressures in excess of about 100 atm. The chief difficulty of using graphite in an oxidizing atmosphere is that the reaction rate becomes quite high at fairly low temperatures. If a threshold oxidation temperature2 is defined as the temperature at which graphite loses 1 pet of its weight in 24 hr, the value in air is 450°, the value in steam is 700°, and the value in carbon dioxide is 900°C. Efforts are presently being made to raise this threshold temperature either by impregnation with a retardant of some type (sodium tung-state and phosphoric acid, for example) or by a suitable metal or oxide coating. It is probably fair to say that, to date, these attempts have not shown any outstanding success in all respects. Most commercial graphites are fabricated by impregnating a carbon flour (say of coke or lampblack particles) with some type of hydrocarbon

Jan 1, 1959

By B. Bryan

The tank car price of gasoline today is controlled by oil in the ground, rather than by stocks of gasoline or methods of refining. Previous to the commercial cracking of fuel oil, there was a normal and continuous relation between gasoline stocks, consumption and prices. From the beginning of the new cracking era in 1923 to the summer of 1926 there was a changing relationship, growing toward a correlation between the potential gasoline in storage and the price of gasoline. Since the development of large reserves of shutin production in Wyoming, California, Seminole, West Texas and Venezuela, the relationship between stocks of gasoline and gasoline prices has disappeared. The extreme depression of the Group 3 price can only be accounted for by oil which is not being produced but which we fear may be produced at any time. In Fig. 1, the curve of gasoline stocks is simply stocks of finished gasoline. The curve of potential gasoline is made by taking 40 per cent. of all stocks except gasoline, kerosene and lubricants, adding to that stocks of finished gasoline and dividing the sum by total gasoline con-sumption to get the months' supply of gasoline at the current rate of consumption. The price curve is the lower figure given by the National Petroleum News for the first quoted date of each month, with the price scale reversed. Stocks of potential gasoline have decrrased from 17 months' supply at the peak of 1924 to a low of 7 months' supply during the past summer, yet the low immediately precedes the lowest price for gasoline since it was a waste product. The tendency of the price curve to parallel the curve of potential supply is quite pronounced until the summer of 1926, since which time they have abruptly separated. The curve of gasolinct stocks is equally remarkable in relation to price when it is considered that total consumption for the year 1927 is almost exactly twice that of 1924. Clearly a new factor has been introduced. There is no possible factor to account for this distortion except known reserves of oil in ground storage, and therefore, until such time as the Bureau of Mines or the

Jan 1, 1928

By G. H. Ruggles

POPULAR opinion, as it might be termed, has always been of the trend that a flotation reagent added to the ball mill during grinding would be more thoroughly mixed with the pulp and for that reason more effective in the production of low tailing. That there are other effects, inimical to good flotation, when using so-called chemical reagents, is brought out by the series of tests outlined in Table 2. It was defi-nitely proved that if either the T. T. mixture (20 per cent thiocarbanalid-80 per cent orthotoluidin) or po-tassium xanthate were added to the ball mill the result-ing flotation concentrate would be lower in copper and higher in insoluble than the concentrate produced by adding these same reagents without the ball mill cir-cuit. With the T. T. mixture four sets of tests were made. The screen analyses of the flotation feed show that there was very little difference in the original grind-ing. When the T. T. mixture was added to the head of the flotation machine the flotation concentrate had a little over 61 per cent solids -200 mesh. If the mix-ture was put into the ball mill the flotation concentrate had but 40.7 per cent of the solids -200 mesh for one set of tests, and 49.0 per cent for the other set. With the mixture at the head of flotation the total concen-trate was high in copper (34.715 and 36.525 per cent) and low in insoluble (13.20 and 11.61 per cent). The assay of the concentrate when the T. T. mixture was introduced into the ball mill was what might be termed low in copper (29.389 and 30.833 per cent). In one of these 'sets of tests (periods 8 to 11, third column) the insoluble was high, 16.81 per cent. The other run (peri-ods 12 to 15, fourth column) for some unknown reason shows a low insoluble, 12.72 per cent. With similar grinding the addition of potassium xan-thate to flotation produced a concentrate having 62.8 per cent -200 mesh, whereas with the potassium xanthate added to the ball mill the flotation concentrate was very coarse, only 36.4 per cent passing 200 mesh. The difference in the total assay of the concentrate is remarkable ; 35.847 per cent copper when the xanthate went to flotation and 30.44 per cent copper when the xanthate was added to the ball mill; insoluble, 10.94 per cent in the former instance, as 22.15 per cent in the latter.

Jan 8, 1927

By K. Torssell, U. Lindborg

The kinetics of precipitation deoxidation is considered from a theoretical point of view. The size distribution and the total content of deoxidation products are estimated statistically as a function of time, taking into account Stokes and gradient collisions between the particles and separation at the top surface of the bath. The assumption is made that two particles coalesce into one larger particle as a result of a collision. General expressions are derived and calculations are carried out numerically for the case of silica particles in liquid iron. The analysis predicts a three-stage behavior for the removal of oxygen, an incubation stage, a stage of rapid separation, and a slow final stage where the content approaches the equilibrium value. The agreement with experimentally determined size distributions and deoxidation times is considered to be good. A quantitative estimation of such growth mechanisms as diffusion from the melt and redistribution of oxygen from small particles to large ones shows that these latter mechanisms cannot explain the experimentally observed gvowth of inclusions. This also indicates that collisions provide the important growth mechanism. OXIDE inclusions precipitate when a deoxidizer like silicon or aluminum is added to a steel bath. The inclusions grow and the large particles tend to separate from the bath. For each type of oxide the growth determines the sizes of the final inclusions as well as the total inclusion content of the steel. The mechanism of growth is controversial, however. It has been suggested that an inclusion grows principally by diffusion of atoms through the melt to the inclusion particle or principally by collisions and coalescence with other inclusions. Diffusion growth is always present to some extent but recent experiments and calculations by Torssell,' Kniippel et 'a1.,2 Sano et al. and Miya-shita4 indicate that collisions may be more important than previously realized. A detailed analysis has so far been lacking. The present paper is a quantitative, statistical analysis of the growth and separation of inclusions and is based on a collision theory. Nuclea-tion is not considered. The numerical estimates are based on the experimental conditions of Torssell's' investigation and comparisons are made with his observations. Torssell' studied the growth and separation of silica particles in liquid iron. Samples were taken from a 0.6 kg iron bath at various times after the addition of silicon. By a particle-counting technique developed by Bergh and Lindber~the size distribution of the inclu- sions was determined. The number of particles at the first sampling, 10 sec after silicon addition, was of the order of 3 x lo7 to 10' per cu cm, the largest particles having a radius of 2 to 4 pm. The volume fraction was 0.001 to 0.004; i.e., the dispersion was very dilute. During subsequent holding the largest particles increased their radius by a factor of 10 after about a minute, and the whole size distribution was displaced toward larger values. These results were obtained with allowance for precipitation of the equilibrium concentration of oxygen during solidification. The bath contained less than 0.01 pct of C. Figs. 1 and 2 show the typical appearance of the inclusions. Most particles are very closely spherical and appear to have been liquid or semiliquid in the melt. The observed number of inclusions, about 5x 10' per cu cm, is of the same order of magnitude as found by ~er~h.' This is a large value. It follows that the diffusion distances are very short and that the precipitation

Jan 1, 1969

By AIME AIME

ON Thursday a most interesting symposium on "Gases in Metals" was held, with both morning and afternoon sessions. The morning was devoted principally to the considerations of the steel maker, the nonferrous field being taken up in the afternoon period. Dr. John Johnston, as chairman, introduced the subject with "A Short Analysis of the Gas-metal Problem and Its Practical Importance." He then introduced P. H. Brace who explained in considerable detail the various vacuum fusion and other methods in use at present, both here and abroad, in the study of "gases" in metals. He was fol¬lowed immediately by H. W. Graham on "The Effect of Oxygen in Steel." The papers elicited considerable discussion, the point being particularly noted by both Dr. Rawdon and Dr. Sauveur that a knowledge of "total oxygen" alone is not sufficient information for the metallurgist, distribution of oxygen being probably the more important. Dr. Johnston, in commenting on the lack of agreement among many of the methods now in use, such as the Ledebur and vacuum fusion, spoke of the contemplated plan of the Iron and Steel Division to have a number of standard samples analyzed by many laboratories by the various methods, the Bureau of Standards acting as a clearing house, so that more definite information may be obtained on the comparative accuracy of the method.

Jan 1, 1933

By R. L. Moment

The anisotropic elastic behavior of rolled beryllium sheet has been measured, using a pulse echo technique, and compared with X-ray diffraction data. Calculated elastic stiffness constants compared favorably with published values for beryllium single crystals which were attributed to the strong (0002) rolling plane texture. Variations of Young's modulus in the yolling plane could be associated with the velative distribution of (0002) planes out of their ideal position in the rollitzg pkule. WHEN a metal is subjected to cold working such as drawing, forming, or rolling, a crystallographic texture develops which can significantly alter its physical properties. One method for detecting this texture is X-ray diffraction, but Alers and Liu' have recently pointed out how the prediction of anisotropic physical properties from pole figures alone is not always accurate due to differences in interpretation. Variations in Young's modulus with orientation or, more completely, the values of the effective elastic constants of the worked metal, also serve to indicate the presence of a texture. In fact, as Alers and Liu' pointed out, calculated variations in Young's modulus for assumed orientations, when compared with experimental data, can be used to eliminate some of the uncertainty in interpretation of X-ray pole figures. Thus, elasticity measurements can serve not only to clarify any unusual elastic behavior of worked metal, but also to detect and in part determine the nature of its texture. X-ray determination of the texture of rolled beryllium has been reported by Smigelskas and Barrett,2 who found a strong texture of (0002) in the rolling plane with (1070) planes normal to the rolling direction. In the case of metal rolled at room temperature, they reported that [1010] directions also appeared at positions 60 and 120 deg from the rolling direction in the rolling plane, while in more recent work Keeler3 found these directions were also tilted towards the rolling plane. The texture for beryllium rolled at 80O0C, however, only showed (1010) planes normal to the rolling direction and the spread of (0002) planes out of the rolling plane was less. In looking for elastic anisotropy one might consider unidirectional rolling of a metal as introducing an or-thorhombic symmetry through reorientation of the grains, since the three deformations, compression, extension in the rolling direction, and extension in the cross direction, are orthogonal to each other and unequal in magnitude. Thus the rolled sheet could be treated like an orthorhombic single crystal and the nine stiffness constants of the elasticity tensor used to calculate the anisotropy of Young's modulus, the shear modulus and Poisson's ratio. In this case we could write: which is symmetric about its diagonal. Borik and Alers4 have recently used this approach on rolled die steel with very good results. They found, however, that instead of displaying orthorhombic elastic symmetry their specimens could be considered tetragonal in which case Cr1 = c22, c13 = Ca, and c44 =cjj. This conclusion was made solely on the basis of the measured tensor elements, and serves to point out the advantage of this method for studying the anisotropy of rolled metals. Their calculated values for Young's modulus as a function of angle in the rolling plane also checked very well with direct measurements made on different specimens using the resonance technique. In the present study, cross-rolled beryllium was used which had been unidirectionally rolled about 11 pct for the final reduction. This imparted a slight anisotropy in the rolling plane which was detected both by X-ray techniques and elasticity measurements. For purposes of discussion in this paper, the rolling direction is that direction in which the most reduction passes were made and cross direction is the normal to the rolling direction in the rolling plane. It was also decided to consider the rolled sheet as displaying orthorhombic symmetry for the purpose of obtaining elasticity samples with the direction defined as in Table I. Any change in the final symmetry attributed to the sheet would then be made on the basis of the measured elastic stiffnesses. The final data would then be compared with that expected from the X-ray study and that reported for beryllium single crystals. EXPERIMENTAL PROCEDURE Rolling Schedule. The samples used in this study were taken from a large sheet which, because of its size, had to be unidirectionally rolled for the final reduction. The resulting texture was that of cross-rolled metal with a slight unidirectional texture superimposed. A cast beryllium ingot, 9.500 in. sq by 3.325 in. thick, was cross-rolled to 81 pct reduction followed by unidirectional rolling for an additional 11 pct to give a total reduction of 92 pct. The thickness of the final sheet ranged from 0.265 to 0.280 in. Reduction up to 67 pct was done at 980°C and the final 25 pct at 870°C. Analysis for metallic impurities showed aluminum 0.06 pct, iron 0.19 pct, and silicon 0.11 pct, giving a beryllium purity of 99.64 pct.

Jan 1, 1968

By R. J. Sandrea, S. M. Farouq Ali

The results of an experimental and theoretical study of the effects of rectilinear impermeable barriers and highly permeable channels on the sweep efficiency and conductivity of a five-spot network are presented. The study was carried out using Hele-Shaw, and conductive sheet analogs for both. normal and inverted flood patterns. A functional relationship was developed which provides quantitative prediction of the above parameters; i.e., sweep efficiency and conductivity, for the nonhomogeneous system. To evaluate this, it is necessary only to measure the interference modulus of the obstacle using a simple expression. The results indicate that impermeable barriers, with an interference modulus greater than zero, always cause a decrease in the conductivity and the sweep efficiency of the pattern. On the other hand, permeability channels do not have a significant effect on these parameters, unless they are located along the streamlines. The study also discusses a method of formulating the difference equations pertaining to the two-dimensional Laplacian in a system containing rectilinear barriers. In addition, a technique is described for tracing the progress of a free surface, using marked particles, in a stream containing discontinuities SuCh as those occurring at the extremities of barriers. The above computational scheme was used in a digital computer program to simulate results of the Hele-Shaw analog. The computed values of sweep efficiency mere in good agreement with the experimental values. INTRODUCTION At the present time waterflooding remains the most widely used technique for the secondary recovery of oil. Among the numerous factors that affect the performance of a waterflood, the areal sweep efficiency constitutes one of the most critical parameters. It is a function only of the geometric distribution of the wells for a homogeneous medium and unit mobility ratio. Geological considerations, however, such as the presence of sealing faults or solution channels in the rock matrix, would generally exert an adverse effect on the areal sweep efficiency of a waterflood network. Surprisingly little information is presently available on the quantitative implications of such permeability interferences. It was the object of this investigation to consider the presence of rectilinear, impermeable and highly permeable interferences in an otherwise homogeneous five-spot pattern, and to analyze their effects on the resulting sweep efficiency and pattern conductivity. The experimental phase of the study was conducted using two different models: the Hele-Shaw flow cell and the field plotter. For experimental convenience, the geometric boundaries of the five-spot were assumed to constitute streamlines even in the case where the interference was asymmetrically placed with respect to a repeated five-spot pattern. A second object of the study was to develop a computational scheme for numerically calculating the pressure distribution in a five-spot flow pattern containing rectilinear, impermeable barriers, and to use this distribution to compute the sweep efficiency. EXPERIMENTAL PROCEDURE HELE-SHAW ANALOG The Hele-Shaw analog was used both as a visual model and for determining the sweep efficiency for systems involving impermeable barriers. The physical limitations of this model as a means of experimentally studying the motion of a fluid in porous medium have been adequately discussed elsewhere.2,7 Likewise, it can be easily verified that the analogy remains valid when a portion of the region between the plates contains an obstacle of the same thickness as the distance between the plates. The model used in this study was composed of

By C. R. Masson, M. L. Pearce

The nitrogen contents of seven specimens of iron and steel were determined by the three methods. Good agreement won generally observed between the results of the isotope -dilution and Kjeldahl determinations, tltzts establishing the reliability of the isotope -dilutzon technique. For some specimens, the vacuum-fusion values at 1650 °C were lower than the corresponding Kjeldahl values by up to 0.0015 pct absolute. These differences were eliminated for a specimen of "pure" iron by performing the vacuum-fusion analyses at 2100 ° to 2240 °C. The reason for this relatively high temperature required m the vaczium-fusion analyses is discussed. ThE determination of nitrogen in iron and steel has been the subject of numerous investigations and a concise review of the extensive literature in this field has recently appeared.' Two methods of analysis are most commonly employed, the vacuum -fusion and the chemical or Kjeldahl method. Except in special cases where the presence of certain alloying elements may present difficulties, both methods are generally regarded as applicable, although the vacuum-fusion method is more sensitive and is often preferred for samples of very low-nitrogen content. The method of isotope dilution, first employed for the determination of gases in metals by Kirshenbaum and Grosse,2 has recently been applied to the determination of nitrogen in iron and steel.3,4 The method is attractive in that it does not require the quantitative extraction of gas from the metal specimen. Staley and Svec3 modified the standard Kjeldahlpro-cedure by introducing, along with the steel sample, a measured amount of ammonium sulfate enriched in the isotope 15N. The nitrogen content was obtained by measuring the isotopic ratio 15N/14N in the resultant solution. The technique involved the distillation of nitrogen as ammonia from alkaline solution and subsequent oxidation of NH4+ in the distillate to gaseous nitrogen. The results for iron and steel samples of commercial origin were often in reasonable agreement with values quoted by the suppliers, although occasional marked discrepancies were observed, particularly with the results of vacuum-fusion analyses. Preliminary work in this laboratory4 on the determination of nitrogen by isotope-dilution in the gas phase yielded results for three samples which were significantly higher than the values obtained by vacuum-fusion. The present paper describes an extension of this work to a wider variety of samples. Analytical results by the Kjeldahl method are also reported. EXPERIMENTAL The technique employed for the isotope-dilution determinations was similar to that described elsewhere.4 Several minor modifications were made to the apparatus. These included the use of molybdenum instead of platinum-rhodium suspending wires when crucibles were degassed at temperatures above 1600°C. The circulatory system used previously for converting CO to CO2 was replaced by a single chamber, the walls of which were cooled directly in liquid nitrogen. Temperatures were measured with an optical pyrometer which had been recently calibrated and, as in the previous study, were minimum values obtained by sighting on the center bottom of the crucible. Temperatures obtained by sighting on the interior walls were always higher by 100' to 130°C with the design of crucible employed. Flat-bottomed crucibles exhibited an even larger temperature difference. To check the efficiency with which crucibles were degassed in the isotope-dilution apparatus, several experiments were done in the vacuum-fusion apparatus, suitably modified4 for isotope-dilution studies. Faster pumping speeds and higher degassing temperatures were possible, the latter due to the use of a generator with a higher power output (10 Kva at 398 kc per sec). In these experiments the combustion of CO was omitted and a correction4 was made for the contribution of CO to the ion current at m/e 28, used in determining the isotopic ratio R = l5NP4N. This correction did not seriously influence the re-

Jan 1, 1962

By L. C. Graton, Joseph Murdoch

I. Introduction......................... 26 1. The Relations of Scale in Geologic Work........ 26 2. General Characteristics of Copper Sulphide Ores..... 29 3. Scope of Present Study................. 31 11. Description of the Important Minerals............ 36 1. Pyrite....................... 36 2. Pyrrhotite....................... 41 3. Chalcopyrite...................... 41 4. Bornite........................ 40 5. Covellite....................... 50 6. Chalcocite....................... 52 7. Enargite...................... 59 8. Tetrahedrite and Tennantite.............. 61 III. Conclusions.......................... 62 I. Introduction. The Relations of Scale in Geologic Work. Many features of human accomplishment rest upon the possibility of representing natural objects on a scale of different magnitude from the actual one. Most drawings, for example, are of very different scale from that of the object depicted, and indeed are useful mainly 011 this account. More important than the question of mere convenience, however, is that of meeting the physical limitations of vision.' Thus, a mural

Jan 1, 1914

By ERNEST A. HERSAY

ACCURATE ore-sizing with screens is drawing attention to certain details that now, more than ever before, require attention. There are many tests that must be preceded by careful sizing. The assayer often could profit by a more careful selection of screens. In milling, more attention is given the slimes produced. Cement-manufacturers are pulverizing and screening finer than they formerly did, and others are reducing materials to fine sizes at high cost, with screens used to govern the fine¬ness of the pulverized product. Fine screens are expensive, easily injured by mis-use, are carried in stock sparingly by most dealers, and are handled often by those who know little about them except their designated number. More attention, on the whole, needs be given the actual size of the mesh-openings, and less emphasis placed upon any custom or conventionality in numbering. An effort to classify wire screens, in this respect, leads at once into computations, where one is confronted with details of sizes and standards, of different wires, different gauges, and different customs. There is always uncertainty about the exact working-size of a screen until one gives the matter special attention, and devotes more time to it than its simplicity seems to demand. To know only the number is not sufficient for all uses. Often, in sets, superfluous sizes are used; and sizes are omitted that are of critical importance. In wire screens, the use of different standard sizes of wire makes important differences in dimensions that must be taken into account. The dealer usually grades screens by the number of openings per linear dimensions, regardless of the size of the openings or of the wire. Certain 100-mesh screens in use are found, by measurement, to he actually coarser than others of 90-mesh, a result which is due, of course, to the use of larger

May 1, 1906

By H. G. Doll

A new electrical logging method. called MicroLaterology is described. whereby the resistivity R of the invaded zone close to the wall of the bore hole is measured. This method essentially utilizes a system of concentric circular electrodes iml,edded in an insulating support which is applied to the wall of the hole. A beam of current of very small diameter is focused horizontally into the formations by means of an automatic control device. and then opens widely at short distance from the wall. with this method, R most often can be recorded directly. except when the mud cake is very thick. in which case a correction is easily provided. The basic role of factor R in the quantitative analysis of electrical logs in terms of fluid saturation and of porosity is explained. The paper is illustrated with field examples. INTRODUCTION In electrical logging. the resistivity of that part of the penneable and porous formations which is invaded by mud filtrate is an important factor in the interpretation. Measurements made with the conventional devices — normal. lateral — and also with improved systems as the Laterolog and induction logging' — are very often more or less affected by the presence of the invaded zone. and the knowledge of the resistivity of this zone is useful in the evaluation of the true resistivity of the beds. which itself is a basic element for the determination of fluid saturation. Moreover. the comparison of the resistivity of the invaded zone with the resistivity of the mud filtrate gives valuable indications on the magnitude of the formation resistivity factor — which in turn is necessary for the quantitative interpretation of the logs. both in terms of fluid saturation and of porosity. On the other hand. it is generally admitted that the invaded zone is not a homogeneous medium separated from the uncon-tamirlated part of the bed hy a well defined cylindrical boundary. but that the fluid distribution—filtrate. connate water. hydrocarbon — and hence. the resistivity. in the invaded zone varies progressively with the distance from the wall of the hole. The term "resistivity of the invaded zone" therefore corre-sponds to an average value which is a function of the distribution of the fluids Inasmuch as the law of this distribution is not exactly known, the resistivity of the invaded zone is not a well defined factor. A much better definition is obtained if the medium under consideration is limited to that part of the formation which is within a short distance from the wall of the hole. It seems likely a within a distance of at least two or three in., most of the fluids in in the pores of tile formation have been displaced by the mud filtrate. The connate water has almost certainly been flushed out. and the oil. if any has generally been reduced to a comparatively small amount. The resistivity witliir~ the radial limit of two to three in. is. therefore. prac.tically constant at an). given level: its value. at least when the proportion of conductive solids in the formation is negligible. is chiefly dependent on the resistivity of the filtrate and on the porosity of the formation, and is affected only to a relatively small degree by the presence of the small amount of residual oil. This part of the formation close to the wall of the hole will he designated in the following as the "flushed zone." a-distinguished from the more general term of "invaded zone'. which relates to the part of the formation extending from the wall out to the distance where the formation is completely uncontaminated. The symbol R,, will he used for the resistivity of the flushed zone. (The notation R is related to the radial distance from the hole. If x designates this distance. xo is the initial value of x, i.e., the value corresponding to the region very close to the wall.) The determination of R is difficult, if not impossible. from logs made with the conventional devices. The long normal and the long lateral are. of course. not suited for this purpose because their radii of investigation are by far too large. The short normal. and the limestone sonde—-after correction for the effect of the hole hole — give resistivity values which corre. spond to materials situated within a comparatively short distance from the hole, but this distance is still several time. as great as the thickness of tire flushed zone. The only value which can be obtained with these devices corresponds to an average resistivity of the invaded zone- — and this only provided the invasion is deep enough, since otherwise the meas "red values would also be affected by the uncontaminated region beyond the invaded zone. It should nevertheless be recalled that despite these limitations. the measurements given by the short normal and or the limestone sonde are always very useful for qualitative interpretation. and also in favorable cases for the qantitative analysis of the logs in terms of saturation and porosity. The MicroLog. which was primarily developed for the detection of permeable beds and for an accurate determination of their boundaries. provides a good approach towards the evaluation of R. In the case of hard formation.. however. The

Jan 1, 1953

Discussion of the paper of DORSET A. LYON and ROBERT M. KEENEY, presented at the Salt Lake meeting, August, 1914, and printed in Bulletin. No. 92, August, 1914, pp. 1791 to 1800. LAWRENCE ADDICKS, Chrome, N. J.-I read this paper for the first time this afternoon, and it is really worthy of a much more careful reply than I can make with such a short time to consider it, but I just want to say that I differ with Dr. Lyon in his premises and conception of what happens in a refining furnace. He cites steel as an instance where the production of special grades justifies the high cost of power in an electric furnace, and goes on to say the same will be true in the case of copper, for the reason that you will get a better quality of product. I don't think you will get a higher grade of copper,. or a better conductivity, as I will explain in a moment. The cost of fuel in the Eastern plants is somewhere between 30c. and 40c. per ton of copper refined, and, if my memory serves me correctly, in an open-hearth steel furnace it is something like $1.25, so it is evident that steel could be handled to better advantage than copper on the basis of fuel. Now, taking the Great Falls plant to compare with is not quite fair, because that plant operates under peculiar conditions. The furnaces are relatively small; the coal is very bad and is very high in sulphur. No one would think of using a coal with 3.6 per cent. sulphur were anything better available. Due to these conditions, the amount of slag is inordinate, it being quoted as 3.5 per cent., and it is necessary to use lime, as there is a tendency to have troubles from arsenic owing to the very high current density used. I think he has taken about as hard a case as he could pick out. Now as to the conductivity of copper, my own idea about the reason that melted copper does not give as high a conductivity as pieces drawn directly from a cathode, or native copper, is that in the latter case the impurities are present as a mechanical mixture, while after melting they are chemically combined with the copper, which is a very different condition. Further, it is necessary to take the sample from a relatively smooth and consequently pure part of the cathode, as otherwise it would not draw. The same with the mass of copper; you pick out a good solid part of the copper, which is not representative. In fact, the refiners have all found they could not take fair samples of cathodes for a chemical analysis. It is always customary to use wire-bar copper -for the purpose of sampling, and the impurities are several times as great as shown by samples taken from .the cathodes. I think if we examine all of the examples he has given of cases where copper is higher in conductivity, it will fit with that explanation. For example, the Elmore process is a direct electrolytic deposit. Incidentally, at the present time there are a number of ex-

Jan 12, 1914

By John W. Buch

IN my review a year ago I pointed out that a small coal-mining companies as well as large had decided that the so called ?central shop? was a benefit. These central shops replaced in a large measure the commercial shops operated by those who have no direct connection with production of cod. Central shops in this time of salvage and major repairs have proved their worth. In addition, many of the larger companies had in their central shops equipment available for the production of many thousands of parts for our vast war machine and, as subcontractors, are doing this type of work. This is a real contribution to the war endeavor. Lack of new supplies has resulted in exhaustion of those stocks formerly stored or hidden in underground shanties. This means that the small stock of repair parts likely LO be available to any mine

Jan 1, 1943

By A. Lee Barrett

MINE power systems are quite different in many respects from those usually found in industrial plants. Wide areas are served, usually by a circuit which is connected continuously throughout the mine. In some mines one circuit may run for several miles. There are usually a small number of branch circuits involved considering the areas covered. In all mines circuits are sectionalized at approximately 2500 ft by means of switches. All, or at least most branch circuits, are sectionalized by manual switches. In some mines automatic sectionalizing gear is used to give automatic overload protection at various strategic points in the system. However at the present time this practice is by no means general. Circuit hazards in mine electric systems are much greater than those encountered in industrial installation. Falls of roof or coal form a prominent hazard which may break the wire and may cause ground faults or partial ground faults. Ordinarily electric cables in mines cannot be insulated, there- fore n fall can easily cause a short circuit. The humidity in most mines is greater than 95 pct and at many points the floor is wet and water may be dripping from the roof over insulators, increasing the difficulties at that point. All electrical circuits must be contained in the mine entries and space must also be provided for moving equipment and men. Consequently, because of the proximity of the power circuit to the locomotives and other moving equipment a considerable hazard is introduced. Mine haulage track is not always good so that wrecks are not unusual. A wreck frequently does consider- able damage to the power circuit. A ground fault frequently results in heavy arcing which may be sustained. If the damage to the circuit is mechanical it may mean that a trip of coal has wrecked and a great deal of coal dust could be thrown into the air as a result of the wreck. The arc resulting from the ground fault could ignite the coal dust and a mine explosion would result. A continued ground fault, even if high in resistance, also may ignite the coal which may be on the bottom of the entry and a mine fire may result. The fire hazard is one of the most serious hazards in any coal mine. Since the mine circuit is completely interconnected, any power interruption resulting from a fault seriously affects the whole operation. Unless the mine is completely sectionalized the whole mine will be shut down until the fault is located and the proper switches are opened to isolate the fault; even then large areas may still be without power if they are supplied by a single power circuit which may be opened in isolating the fault. Further, mine power is usually supplied from a relatively small number of substations and the fault may be on a stub feed circuit, in which case power cannot be restored until the fault has been cleared. Practice varies widely with respect to placement of substations. Usually they will be spaced from I to 2 miles in 500V operations, and at 1 mile intervals or less, in 250 V operation. Actual mining operations govern substation placements and no general rules can be followed.

Jan 1, 1948

By D. C. Hilty, W. Crafts

J. Chipman—It has been my privilege to discuss this work with the authors on several occasions and to observe at first hand the experimental methods employed. I wish, therefore, to emphasize certain points which they have mentioned only briefly with regard to the experimental techniques. The rotating induction furnace as here employed interposes liquid metal between slag and refractory thus preventing the two nonmetallic parts of the system from reaching equilibrium with one another. It is therefore impossible for the metallic phase to be completely in equilibrium with both the slag and the crucible. The metal also acts as a partially permeable membrane allowing certain components, including oxygen, to diffuse from slag to crucible. This transfer results in building up on the face of the crucible a layer of material whose composition is in part dependent on that of the bath. Reactions between the layer and the solid refractory are slow, as evidenced by the rather good life of the crucible. Hence it seems probable that the layer is more nearly in equilibrium with the metal than with the underlying crucible material and that, once it is established under a bath of a given composition, its further reactions with that bath are slow. Additions to slag or bath may be followed by changes in the layer; and time must be allowed for virtual completion of such changes, before it can be assumed that slag and metal are in equilibrium. We may judge from the results reported that, in general, this was the case and that the data represent at least quite close approximations to slag-metal equilibrium. Data on deoxidation and on oxygen solubility are no better than the analytical methods employed. The vacuum fusion method as used by the authors seems entirely adequate for the samples analyzed. I have had frequent occasion to compare results with their laboratory, always with very satisfactory agreement. The determination of aluminum at very low concentrations is perhaps an even more difficult procedure. Here also the colorimetric method used has been worked out with great care and is undoubtedly the most dependable method available. The discrepancy between observed and calculated deoxidation or solubility lines is not to be explained as the result of experimental errors, either in the sampling or analysis of the metal. Nor is it to be blamed upon inaccuracies in the several kinds of indirect data upon which the calculated results were based. It is true that both the observed and the calculated lines admit of some uncertainty as to their exact locations, but the uncertainties are small compared to the wide gap which separates the two lines. The authors have pointed out the real cause of the discrepancy. In all of their experiments the solid phase was not Al2O3 but a mixed oxide containing iron and aluminum. This suggests an extension of the calculated values to include equilibrium with the spinel FeO . A12O3. The free energies of FeO and A12O3 are known, that of the spinel is not. However, it cannot differ greatly from that of its component oxides for even in the more stable spinel, chromite, the free energy of formation from the oxides is less than 10,000 cal. For purposes of calculation we shall call this free energy X and solve for values of X lying between zero and 10,000 cal. The other data required are taken from the forthcoming revision of "Basic Open Hearth Steelmaking" and are given in the following equations in which underlined symbols indicate elements dissolved in liquid steel and the standard concentrations are 1 pct. ?F° at 1600°C, cal ?LA = 2 Al + 3 O; + 107,200 FeO = Fe + 0; + 5,460 FeO + A12O3 = Fe + 2A1 + 4 0; + 112,660 — X The corresponding equilibrium concentrations are shown in fig. 21. The line marked A12O3 corresponds to the first equation, those marked FeO . AL2O3 correspond to the last, with X = 0, 5000 and 10,000 cal, respectively. The two upper lines represent the data of Hilty and Crafts and of Wentrup and Hieber. The points are the observations of Hilty and Crafts in the presence of 0.50 pct Mn.

Jan 1, 1951

By Herbert Hoover

IT is always a pleasure for me to join in the Ameri-can Mining Congress, for not only has my own professional life been closely linked with the industry, but the Secretary of Commerce is specifically enjoined in the organic act creating the office to promote and foster the interests of the mining industry. And it is a vital part of our national life. It is one of those indus-tries without which. the nation could not go on for a week. It ranks second only to the agricultural industry in its contribution to our raw materials. Its production amounts to nearly 6 ½ billions annually, providing direct support to probably ten millions of our people through employment to about two million workers. But the in-dustry has a greater importance than even these figures indicate, for with agriculture, forestry, and water power it furnishes the raw materials upon which the whole work of our civilization rests. When the raw ma-terials of our mines emerge. from manufacture with the added expenditure of labor and capital upon them, they have a wholesale value of over fifteen billions of dollars. And in this, the second stage of their application, they give employment to another two million workers and support to about ten million more of our people. A large portion of these manufactured commodities must filter through the retail trade; their total value when delivered to the consumer exceeds twenty billions of dollars. And from this distribution arises the support of many more millions of our people. It is estimated that the products of agriculture when they reach . the consumer, with transportation, manu-facturing, and distribution costs added, have about the same value as the mineral industries-each of them thus contributing about one-quarter of our total na-tional income. No other continent has demonstrated its possession of such a magnitude of minerals as has ours, and such a bountiful distribution over our whole land. But our mineral resources differ in one essential from our other natural resources-they are not renewable. Agricul-ture, forests, and water power replenish their supplies from season to season. Some people conclude from the non-renewable character of the mineral supply that they must shortly be exhausted. The practical question is ,one of time, and time in these matters needs to be measured in generations, and apprehension of exhaus-tion needs to be tempered with many probabilities in-cluding the advance in technical methods of extraction. In some of our minerals, such as coal, iron, and building materials we can, through a knowledge of their geologi-cal structure and occurrence, make fairly good estimates of our reserves. We. know that they will outlast many generations of Americans. In non-ferrous metals and oil, geology affords us no great basis for an estimate of future supply. We only know of the occurrence of minerals of this type by actual exposure of them, and we can thus make no estimates except upon reserves which have been proved by actual development by the process of mining. To develop them ahead merely for national satisfaction of assured future supply would imply an unbearable waste of capital. The consequence is that in these groups there is never a demonstrable assurance of more than a few years' supply ahead of us. Yet we have never failed from year to year to find new deposits and extension of old deposits.

Jan 1, 1928

CONTENTS RUSSIA-R. C.-BECKSTROM 3 VENEZUELA-F. H. KAY 9 TRINIDAD-W. J. MlLLARD 20 RUMANIA-1. I. GARDESCU 26

Jan 1, 1932

By H. G. Turner

The coals mined in the area known as the anthracite fields of Pennsylvania have always been recognized commercially as anthracites. In the literature, however, some of these anthracites have been called semi-anthracites by various writers. The coals mined in Sullivan County, especially those from the Bernice field, have been recognized commercially both as anthracites and semi-anthracites. In the literature they have almost always been referred to as typical semianthracites, although Franklin Platt,1 in his report to the Pennsylvania Geological Survey, uses the terms semibituminous, semianthracite, and anthracite in describing them. The purpose of this paper is to endeavor to dispel the confusion of names used to describe these coals and to supply further information that will permit a logical and definite classification. Most of the confusion of the past has been due to the impossibility of securing enough fresh face samples from which to draw sound conclusions; some of it was due, no doubt, to lack of standard methods of analysis, and of course, to the ever-present lack of definition of boundaries from the standpoint of classification. Map Showing Lines of Equal Volatile Matter and Lines of Equal Specific Gravity As a foundation for this work the writer constructed a map showing lines of equal volatile matter and lines of equal specific gravity throughout the anthracite and semianthracite regions. The points on these lines were determined from a study of analyses of 214 face samples from 28 mines and composite analyses from 18 different breakers. These samples were collected through the joint efforts of the U. S. Bureau of Mines and the Anthracite Institute. The Bureau of Mines standard method of sampling was used in all cases. All analyses were made by the Bureau of Mines and are used here with its permission. The

Jan 1, 1934

By Scott Turner

IT has been considered that the training of an engineer is too often vocational training; that it is a pity all engineers cannot have had a period of liberal training before taking up' pure engineering. Offhand, the so-called liberal courses should bring more ready adaptability to deal with the unexpected, to face with assurance situations which have had no parallel in one's experience, and to move without hesitation under conditions which were heretofore unknown to one, than the specialized course in mining engineering. We hear increasing talk as to the necessity of making the engineer articulate and bringing him into public life. The social implications, and responsibilities of engineering are pointed out, as of equal importance with the prodigious marvels of engineering ingenuity. You often read of this as the logical result of the in¬creasing consciousness of the engineer as to his rela¬tive position in our modern industrial civilization. , Some wag has noted that man is the noblest work of God, but that man is the only one who has said so. Perhaps engineers are the only claimants as to the necessity of their going in for public life and service; at any rate, some liberal educators' still maintain that a well-rounded general education is the better training.

Jan 1, 1930