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By P. A. Larssen, P. R. Gage, R. W. Bartlett

The kinetics of formation of intermediate sili-cide compounds from MoSi2/Mo and WSi2/W couples were studied using a cylindrical sample configuration. Concentration profiles of the constituent metals were deter mined from electron-microprobe analysis of cross-sectioned samples after isotlzernzal diffusion annealing. These data also yielded hand widths of phases. Growth of intermediate phases depends on diffusionin them and obeys a parabolic rate law. The rates of formation of the intermediate phases decrease in the order Mo5Si3 > W5Si3 > Mo3Si. Crowth rates. for the isomorphous phases Mo5Si3 and W5Si3 had the same activation energy. 43 kcal per mole. SILICIDE coatings employed to protect refractory metals from high-temperature oxidation are usually formed by a diffusion process requiring concurrent transfer of silicon to the refractory metal surface. For a simple binary system and a coating thickness of one or two mils, the coatings on molybdenum and tungsten are primarily the disilicides WSi2 and MoSi2, respectively. During use of the coated re- fractory-metal system at high temperatures, in the absence of the silicon source, further diffusion causes growth of lower silicide compounds and depletion of the disilicides. Recent investigations have shown that the lower silicides are less effective than the disilicides in forming a glassy oxide film which impedes oxidation.' Consequently, failure of coatings at high temperatures may coincide with complete conversion of the disilicide phase. The purpose of this part of the study is to investigate the growth kinetics of the intermediate compounds in the W-Si and Mo-Si systems. There are three intermetallic compounds in the Mo-Si system: MoSi2 with a tetragonal structure

Jan 1, 1964

By R. F. Mehl, J. K. Stanley

THE recrystallization of cold-worked metals is studied ordinarily by determining the temperatures required for complete recrystallization to occur within a given arbitrary time period, usually within 15 min. to 2 hr. The results obtained are conventionally assembled in a three-dimensional diagram relating this temperature to the amount of cold-work (percentage deformation) and the resultant grain size, though sometimes other modes of representation are employed.1 Such three-dimensional diagrams are not complete, for the number of variables exceeds the number represented. The process of recrystallization is characterized by a time-rate, a fact that is not portrayed upon ordinary recrystallization diagrams. It is known that recrystallization consists in the formation of new nuclei and the growth of these nuclei, a process that continues until the matrix is completely consumed and the original set of grains entirely replaced by the new. This knowledge is old.2 Truly heterogeneous reactions invariably proceed by nucleation and growth; the decomposition of eutectoid solid solutions provides an example about which much is known,3 and freezing, originally studied by Tammann, provides the classic example. Although recrystallization is not a heterogeneous reaction within the orthodox meaning of the term, the mechanism of the process is the same. As in eutectoid inversion and freezing, it should be possible to study the rate of isothermal recrystallization as a function of time, and it should also be possible to analyze the isothermal reaction curve into the component rates of nucleation and growth that determine them.* Other methods, not employing the rates of nucleation and growth, have been used to represent the rates of such reactions, but these in general have been artificial and have not led to progress .4,5† The theory of recrystallization is not in advanced state; if recrystallization data were obtained in terms of the rate of isothermal recrystallization, and in terms of the rate of nucleation and the rate of growth of recrystallized grains, and in particular if the temperature coefficients of these rates were measured accurately, an adequate theory should be more readily developed .27 Such an effort requires proper experimental technique, but especially requires suitable methods of mathematical analysis to convert measurements made upon a surface of polish into values for the rate of nucleation and the rate of growth and to combine these into a rate of isothermal recrystallization. These methods are now

Jan 1, 1942

By B. Silliman

The regions of New Mexico referred to are in Socorro, Grant, and Dona Ana counties, and a portion of Lincoln County, embracing in the aggregate a very large area, of most of which our knowledge is as yet very fragmentary and superficial. It is only very recently that large portions of this region have been accessible. It has been full of danger from hostile bands of wandering Apaches, whose murderous raids have slain many adventurous miners and seriously prevented developments. But this evil has now been largely abated, and in many of the mining camp of this region there is no longer any danger from this cause. SOCORRO MINES. About three and a half miles back of the old Mexican town of Socorro, on the Rio Grande, chief town of the County of Socorro, are two or more large veins of heavy spar, cutting across the fat* of Socorro Mountain in a northeast and southwest direction, and dip ping at an angle of about forty degrees into the body of the mountain. These veins are in rhyolite, and, so far as could be seen in openings on the Torrence Mine, which I examined, are without any clay parting or selvage. The average thickness of the Torrence rein may be about five feet, the thickness varying from pne or two feet to thirteen feet. Upon the cleavage planes of the heavy spar occurs, in visible patches, of a waxy Iustre and gray color, silver chloride, which gives value to the vein, from a few ounces up to one hundred and twenty ounces to the ton, averaging about forty ounces, as I

Jan 1, 1882

By Lauren A. Wright

SINCE the early nineteen-thirties the production of talc* in California has increased five-fold to a yield in 1947 of about 76,000 tons (fig. 1); conse- .' Unless otherwise qualified, the term "talc" in this paper will imply a mixture of the pure talc with such related minerals as commonly occur in the commercial material. quently the state is now one of the nation's three principal talc producers. The 1947 output, which represented about one-sixth of the national total for that year, was approximately equal to production from Vermont, and was second in value to that from New York. New York has an annual output of about 130,000 tons. Three factors have been mainly responsible for the expansion of talc production in California. (1) Technical advances and innovations, particularly in the ceramic industry, have increased the demand for certain California talcs. The nation's high-qual- LAUREN A. WRIGHT, Junior Member AIME, is Associate Geologist, California Division of Mines, San Francisco, Calif. Los Angeles Meeting, October 1948. San Francisco Meeting, February 1949. TP 2622 H. Discussion of this paper (2 copies) may be sent to Transactions AIME before Feb. 28, 1950. Manuscripts received Dec. 7, 1948; revision received Aug. 29, 1949. This paper is Contribution No. 508 of the Division of Geological Sciences, California Institute of Technology, Pasadena, Calif. the industry, mainly through demand for the urgently needed steatite. Fibrous talc, used as a paint extender by the armed forces, also was produced in quantity. (3) Expanding western industry has continued to draw heavily on California talc deposits, and has extended the upward production trend into the postwar period. Considerably more than half of California's current talc output is used as ceramic raw material. The paint, rubber, paper, and textile industries are the more important consumers of the remainder. Smaller amounts are used as insecticide carriers, and in cosmetics, and various minor industrial applications. During World War I1 the principal steatite deposits were studied in detail by members of the U. S. Geological Survey; other sources of commercial talc in the state have in the past received but scant geologic attention. The following discussion is essentially a preliminary report based on research currently in progress by the California Division of Mines, and includes a brief outline of previous steatite studies by the U. S. Geological Survey. Distribution of California Talc Deposits: The principal talc resources of both California and Nevada are confined to an elongate belt that extends from the vicinity of Baker, in north-central San Bernardino County, northwestward to include the southern Death Valley region, the Inyo Range, and the Palmetto-Oasis district of western Nevada (fig. 2). This belt, of which all but the northernmost tip lies in California, is approximately 200 miles long and 30 miles in average width. Included in the belt are four contrasting areas. The deposits within each area are geologically similar and yield talcs that have characteristic properties and applications. Three of these local "talc provinces" lie within California's portion of the talc-

Jan 1, 1951

By Lauren A. Wright

SINCE the early nineteen-thirties the production of talc* in California has increased five-fold to a yield in 1947 of about 76,000 tons (fig. 1); conse- .' Unless otherwise qualified, the term "talc" in this paper will imply a mixture of the pure talc with such related minerals as commonly occur in the commercial material. quently the state is now one of the nation's three principal talc producers. The 1947 output, which represented about one-sixth of the national total for that year, was approximately equal to production from Vermont, and was second in value to that from New York. New York has an annual output of about 130,000 tons. Three factors have been mainly responsible for the expansion of talc production in California. (1) Technical advances and innovations, particularly in the ceramic industry, have increased the demand for certain California talcs. The nation's high-qual- LAUREN A. WRIGHT, Junior Member AIME, is Associate Geologist, California Division of Mines, San Francisco, Calif. Los Angeles Meeting, October 1948. San Francisco Meeting, February 1949. TP 2622 H. Discussion of this paper (2 copies) may be sent to Transactions AIME before Feb. 28, 1950. Manuscripts received Dec. 7, 1948; revision received Aug. 29, 1949. This paper is Contribution No. 508 of the Division of Geological Sciences, California Institute of Technology, Pasadena, Calif. the industry, mainly through demand for the urgently needed steatite. Fibrous talc, used as a paint extender by the armed forces, also was produced in quantity. (3) Expanding western industry has continued to draw heavily on California talc deposits, and has extended the upward production trend into the postwar period. Considerably more than half of California's current talc output is used as ceramic raw material. The paint, rubber, paper, and textile industries are the more important consumers of the remainder. Smaller amounts are used as insecticide carriers, and in cosmetics, and various minor industrial applications. During World War I1 the principal steatite deposits were studied in detail by members of the U. S. Geological Survey; other sources of commercial talc in the state have in the past received but scant geologic attention. The following discussion is essentially a preliminary report based on research currently in progress by the California Division of Mines, and includes a brief outline of previous steatite studies by the U. S. Geological Survey. Distribution of California Talc Deposits: The principal talc resources of both California and Nevada are confined to an elongate belt that extends from the vicinity of Baker, in north-central San Bernardino County, northwestward to include the southern Death Valley region, the Inyo Range, and the Palmetto-Oasis district of western Nevada (fig. 2). This belt, of which all but the northernmost tip lies in California, is approximately 200 miles long and 30 miles in average width. Included in the belt are four contrasting areas. The deposits within each area are geologically similar and yield talcs that have characteristic properties and applications. Three of these local "talc provinces" lie within California's portion of the talc-

Jan 1, 1951

By Leon T. Eleiel

Ten years ago a broad knowledge of aerial mapping, coupled with a smattering of geology, qualified one to speak on the subject of the application of aerial mapping to geology. Today, with aerial maps a common tool in the hands of expert geologists on every continent throughout the world, it would be nothing short of presumptuous for the author of this paper, who is not a geologist, to give any geological statements on his own authority. Relatively, today we are only purveyors of general geological gossip, with a definite case here and there by way of illustration. But we can present a story of the really marvellous strides that have been made in the evolution of aerial mapping, built around a skeleton of geological tidbits, from which some useful conclusions may be drawn. The average geologist goes about reading his aerial maps much as one would approach the problem of deciphering a cryptogram. To begin with, typical key expressions appear in recurring sequences and under certain conditions. If once the meaning of these isolated bits of information can be ascertained, the message begins to take meaning. In a similar fashion, the geologist works out his key from aerial maps of territory with which he has some familiarity. He learns that a certain type of thin, white line may mean a vein of quartz. He sees that a certain change in the photographic tone of vegetation on the ground reflects two kinds of soils on opposite sides of a contact. He sees that a certain type of alignment of topographical features often means a fault. He learns that by the erosion pattern he can frequently distinguish soft formations from harder ones. And so, bit by bit, he ties together the information of the picture with his experience on the ground until he develops a reasonably creditable capacity of interpretation. Through the complete gamut of surface conditions, ranging all the way from flat, arid, exposed desert terrain to dense jungle, or rugged mountains, the evidence from which the geologist must make his interpretation varies with bewildering profusion. The quality of photographs which are obtainable may range from perfect pictures in the desert to almost useless smudges in the steaming jungles. One thing he has learned with certainty—the airplane carrying its mapping camera is a superb reconnaissance tool, only awaiting his ingenuity in correlating the pictures with the ground to simplify most exploratory problems.

Jan 1, 1937

By Anson Hayes, John Chipman

The quality of sheet and strip products made of rimming steel is closely related to the structure and chemistry of the ingots. The variation in composition throughout the ingot, as affected by segregation, is of great importance, as are also the form and distribution of the voids that result from the gases evolved. It is because of this importance that the considerable literature in this field has accumulated. No attempt is made in the present paper to compile a bibliography of the excellent work that has already been done, as this has been adequately covered in the many excellent reports on the heterogeneity of steel ingots prepared by a joint committee and published by the Iron and Steel Institute.' From time to time, in any field of investigation new tools and new technique are developed, which make further progress possible. In the field with which this paper is concerned, this is true. The development of the vacuum-fusion method as a means of following oxygen segregation, and a technique for obtaining the volume and composition of the gases evolved during solidification, have opened the way to obtaining data by means of which some considerable progress has been realized in developing more of the detailed mechanisms of solidification and segregation in rimming-steel ingots. General Theory of Segregation The basic cause of segregation lies in the fact that the impurities are less soluble in solid than in liquid iron. The solid that forms from the impure liquid is more nearly pure than the liquid itself. If solidification proceeds slowly enough, or if the liquid and solid phases are maintained in contact with one another for a sufficient time, a condition of equilibrium is set up, which may be represented by a phase diagram. Portions of the

Jan 1, 1939

By Anson Hayes, John Chipman

The quality of sheet and strip products made of rimming steel is closely related to the structure and chemistry of the ingots. The variation in composition throughout the ingot, as affected by segregation, is of great importance, as are also the form and distribution of the voids that result from the gases evolved. It is because of this importance that the considerable literature in this field has accumulated. No attempt is made in the present paper to compile a bibliography of the excellent work that has already been done, as this has been adequately covered in the many excellent reports on the heterogeneity of steel ingots prepared by a joint committee and published by the Iron and Steel Institute.' From time to time, in any field of investigation new tools and new technique are developed, which make further progress possible. In the field with which this paper is concerned, this is true. The development of the vacuum-fusion method as a means of following oxygen segregation, and a technique for obtaining the volume and composition of the gases evolved during solidification, have opened the way to obtaining data by means of which some considerable progress has been realized in developing more of the detailed mechanisms of solidification and segregation in rimming-steel ingots. General Theory of Segregation The basic cause of segregation lies in the fact that the impurities are less soluble in solid than in liquid iron. The solid that forms from the impure liquid is more nearly pure than the liquid itself. If solidification proceeds slowly enough, or if the liquid and solid phases are maintained in contact with one another for a sufficient time, a condition of equilibrium is set up, which may be represented by a phase diagram. Portions of the

Jan 1, 1939

By J. Campbell

The negative pressure developed within a solidifying sphere of pure iron is investigated theoretically assuming an elastic-plastic model. The maximum hydrostatic tension attainable is shown to be an order of magnitude smaller than that required for the homogeneous muclealion of pores in the liquid cove, and four orders of magnilude smaller than that predicted from) a rigid shell model. It is well-known that liquids can withstand large hydrostatic tensile stresses, or negative pressures. The various experimental investigations of the tensile strengths (often called the fracture pressures) of liquids are reviewed by Dean,1 and the theoretical attempts at estimating fracture pressures are critically assessed by wakeshima.2 Using Fisher's3 quation, the fracture pressure of pure liquid iron is about -70,000 atm, which may be too large by as much as a factor of 4, but is certainly correct to within an order of magnitude.' In view of the great importance of the problem of the nucleation of shrinkage cavities in castings it is of interest to determine exactly what tensile stresses can exist in the residual liquid in a solidifying casting; it has often been assumed that, because of the very low strengths of solid metals near their melting points, no interior stresses are developed at all. Nussey4 has determined theoretically the pressure in the liquid core of a solidifying metal sphere assuming that the solidified shell does not deform (i .e., is perfectly rigid), so that because of the contraction accompanying solidification (a) (about 3 pct for most metals) the progressive deposition of solid onto the inner surface of the shell causes the remaining liquid to be expanded to make up this difference in volume. This leads to a relation between the pressure P in the liquid, the initial pressure, PO, the bulk modulus of the liquid, K, and the inner and outer radii of the solid shell, o and b, respectively:

Jan 1, 1968

By Paul E. Richardson, Edwin E. Maust

Cyclic voltammetry and surface potential (photovoltage) measurements have been carried out on galena electrodes in sodium tetraborate solutions with added HC1 and NaOH to adjust the pH over the range 2 to 13. The first technique shows that the surface species formed on moderate anodic polarization and reduced on subsequent cathodic polarization are the same over the entire pH range. At anodic potentials, a soluble metal species and excess sulfur are formed; at cathodic potentials, sulfur is reduced to a soluble species. More importantly, excess surface sulfur is formed spontaneously under zero current conditions in alkaline solutions. This has been shown to occur on both polished surfaces and on virgin surfaces produced by in situ cleavage under the electrolyte. The photovoltage gives some insight into the charge and potential distribution at the galena surface. This is found to depend on past electrochemical history and the n- or p-type semiconducting character of the electrode and is interpreted in terms of changes in the surface stoichiometry that occur during reduction or oxidation. The effect of surface stoichiometry on subsequent xanthate interactions is discussed.

Jan 1, 1976

By M. Van Siclen

THE outstanding fact in connection with dust disease in the United States at present is the growing recognition of its seriousness by state officials and by the more progressive operators of mining, metallurgical and allied industrial plants. The same may perhaps be said of labor in some of its better organized centers, but the average independent non-union workman continues, as of yore, to suffer the toll of disability and even of death from dust inhalation without realization of the source of his ill-being. Progress in the betterment of the handling of sufferers from dust disease and of the conditions creating dust hazards in mining and allied industries is pursuing a course similar to that of the now widespread campaign against accidents, in which the risk is more obvious, more severe, and was naturally recognized sooner. The coming on of dust disease is generally relatively slow and its immediate effects not infre¬quently masked by or attributed to other diseases. Marked exceptions to this general rule have occurred in districts where the dust is particularly pernicious, such as the Rand and Joplin; yet such exceptions, unhappy in themselves, opened the eyes of medical men, and of those in other localities charged with the responsibility for the welfare of industry, to the much more widespread if less spectacular hazard. existing from the inhalation of dust in all rock-excavating operations and all industrial operations creating inorganic dust, whether it be crushing and grinding, sand-blasting, granite-cutting, or what not. Advancement to date in the United States in prevention and treatment has been slow, yet the record shows that quantitative methods for determining the degree of hazard and means for decreasing it were being developed as far back as 25 years ago; and that more rapid progress may be looked for from now on. In 1908, in this country; F. L Hoffman?(1) discussed the mortality from consumption in dusty trades, especially brass foundries; and in 1913 E. R. Hayhurst(2) described the effects of inhalation

Jan 1, 1933

By H. M. Chance

The iron-ore deposits of the Hartville district are located near the new town of Guernsey, about 100 miles north of Cheyenne. The writer has been familiar with them since 1887, having visited the district several times for different clients— his last examination having been made in November and December, 1897. The deposits extend in a general N.E.-S.W. direction from a point in Section 33, Range 65 W., Township 28 N., on the west side of Whalen cañon, through Sections 4, 5, 6, 7 and 8 of Township 27 N. in the same Range, and over into Sections 1 and 12 of Township 27 N., Range 66 W. General Characteristics. The ore is a remarkably pure red hematite, extremely low in phosphorus, and carrying a small percentage of silica, as shown by analyses given below, and similar in many respects

Jan 1, 1901

By L. H. Robinson

Triaxial compression tests have been performed to determine the strength characteristics of limestone, sand-stone and shale rocks subjected to controlled stress conditions. This control tuns exercised by varying the liquid pressures within and around a plastic-encased rock specimen. The pressure in the pores of the rock was varied throughout the range from atmospheric to 15,000 psig; the external pressure was changed over the same range with various positive pressure differences between is and the intertnal pressure. The data show that the rock strength increased and the mode of failure changed as the pressuire. surrounding the rock became greater than the pressure in the pores of the rock. These observations and the resu1ts of microbit drilling experiments indicate that the increased rock strength under pressure may bc an important effect in reducing drilling rare, but that other factors are probably of even greater importance. INTRODUCTION A large part of the research conductcd to reducc thc cost of drilling is directed toward improving present drilling technology and dcveloping new drilling methods. In spite of the fact that drilling is essentiaIly the act of making rocks fail, many details of the mechanism of failure are not known. It seems probable, therefore, that continuing studies of the fundamentals of rock failure can lay a foundation for future improvements in drilling technology. One of the factors which affects rock failure is the stress applied to the rock. This effect has been known for many years.'.'.; As an example, stress studics have been published by engineers' concerned with the strength characteristics of concrete in large dams. More recently, a number of investigators4-12 have explored the effects of stress on the strength of geologic formations and the geologic implications of their findings. During the last few years some research'" on rock strengths has also been conductcd in an attempt to gain additional insight into the factors which affeet rock drillability. In detcrmining the strength characteristics of rocks under different stress conditions, investigators have conventionally used triaxial compression equipment. wherein a jacketed rock cylinder is uniformly loaded from all directions and then compressed longitudinally. The results of this work have demonstrated that the mode of failure (brittle or malleable) is dependent upon the loading pressure, and that the strength of the rock increases as the loading pressure increases. These results clearly manifest that the stress, which is determined by the loading pressure, affects rock strength, and this implies that rocks under stress should be stronger and hence harder to drill. During the drilling of a porous rock the stress conditions are determined not only by the pressure surrounding the portion of the rock undergoing failure (confining pressure) but also by the pressure of the interstitial fluids within the rock (pore pressure). The importancc of both these pressures on the drilling rate of rocks has already been demonstrated by a number of investigators. Murray and Cunningham" found in microbit drilling expcriments that at constant pore pressures the drilling ratc decreased as the hydrostatic pressure surrounding an unjacketed, impermeable rock increased. Later Eckel" found that for jacketed Iimestone specimens the differcnce between hydrostatic (wellbore) pressure and formation (pore) pressure had an important effect on drilling rate. These observations of the effect of pressure on drilling rate emphasize that for drilling studies triaxial compression tests should be conducted under conditions of confining and pore pressure which simulate conditions underground. In the past, triaxial tests have been made under conditions which do not reproduce those underground. In particular, most of the tests on porous materials have keen made at varying confining pressures but with atmospheric pore pressures. In only one group of tests' was any data on the effect of pore pressurc reported, and these few data were on materials not representiltive of those encountered in drilling earth formations. The research described herein was initiated to deter-mine the importance of both internal pore pressure and confining pressure on failure characteristics of limestone. sandstone and shales. Triaxial loading equipment was used to obtain strength data at pressures up to 15,000 psig. An additional objective of this research was to apply these results to drilling rate studies by comparing them with the previously published drilling data of Murray and Cunningham" and of Eckel12. The work reported here is but one step in determining and evaluating the fundamental mechanisms which control drilling rate. Additional research is needed to clarify other aspects of the drilling process. The better

By S. F. Emmons

This mine is situated upon the western slope of the Meadow Valley mountains, about 70 miles by road from the present end of the railroad-track, which is at Uvada, on the UtahNevada boundary. This boundary-line marks fairly well a certain change in type of scenery from western Utah to eastern Nevada,—from a region in which the desert valleys predominate over the mountain ranges to one in which they are in about equal proportion. The railroad from Salt Lake City runs somewhat W. of S., for the most part along the bottom of the ancient Lake Bonneville. The latter part of its present course follows the axis of the southern arm or bay of that lake, now known as the Escalante desert. Along this bay, its line is a mathematically straight one, with no perceptible change of level for two " tangents " of more than 30 miles each, varying but a few degrees in direction. In the four or five hours re-

Jan 1, 1902

By T. A. Rickard

In a former paper* the writer has described the essential features of the general geology of the Cripple Creek region. In the present account it is intended to examine into the occurrence of the ores, the value of which has made this district the most important among existing American gold-fields. The production of Cripple Creek from its discovery, in 1891, to the close of 1901, has reached a valuation of fully $125,000,000. During the past year (1901) the output amounted to $17,285,470. In 1900 it was $18,174,681. The first discoveries, which led to the development of the district, were made in the spring of 1891, but it was not until 1893 that vigorous work was commenced. A great impetus was then given to the exploration for gold on account, of the sudden drop in the market-price of silver, caused by the closing of the Indian mints in the summer of that year. This induced an energetic population from the older silvermining camps of Colorado to go to the new gold-field, which was then beginning to attract attention. Prospecting, at first, was hindered by the comparative absence of outcrops, due to the fact that the surface of the hills is covered with a considerable thickness of shattered rock, resulting from the action of frost at a high altitude; but so much indiscriminate digging was done that a number of rich veins were uncovered, and this stimulated the search for others. The advanced condition of the mining industry of Colorado offered unusual facilities for exploration and reduction; progress was therefore rapid, with the result that the district soon achieved great prominence.

Jan 1, 1903

By N. Mungan

A study was made of the effects of wettability and interfacial tension on the immiscible displacement of a Iiquid by another Iiquid from porous media. The influence of viscosity ratio was also investigated. Porous media used were polytetrafluoroethylene (TFE) cores prepared by compressing TFE powder under different pressures. lt is shown that displacement of a wetting by a nonwetting Iiquid is always less efficient than the displacement of a nonwetting by a wetting fluid, all other things being equal. In the former case, the recovery efficiency can be increased substantially by either reducing the interfacial tension or increasing the viscosity of the displacing fluid. A qualitative discussion is given on the implications of this work to the recovery of crude oil by water flooding. INTRODUCTION The high cost of oil exploration and new recovery schemes makes it imperative that waterflooding be conducted under conditions favoring most efficient oil recovery. To improve oil recovery by waterflooding, it is essential that the role played by interfacial forces in the entrapment of residual oil be studied and understood. Interfacial phenomena in natural rock, connate water and crude oil systems are very complicated because of the complexity of the natural liquids found in petroleum reservoirs, because of our inability to adequately describe the geometrical structure of the porous media and because of a lack of understanding of physical and chemical interactions between the liquids and surface of the pores. The problem becomes further complicated when one tries to elucidate the role of interfacial phenomena in fluid flow. Numerous studies of the displacement of oil by water under different interfacial tension or wet-tability conditions have been made.lm3 These studies have been performed in silica, alundum or sandstone systems using water and paraffin oil and also some surface active material to control the interfacial tension s and the contact angle 0. Unfortunately, the high energies of various interfaces involved favor adsorption and orientation of the surface active material at the interfaces. Also the surface active material concentration at the interfaces exceeds that in the bulk of the liquid phases. Such surface excess may cause the surfactant distribution, the contact angle and the interfacial tension to differ from their measured static equilibrium values and makes interpretation of the displacement experiments difficult. Furthermore, as changes in s also lead to changes in cos 0, the role played individually by one of these parameters in the displacement becomes obscured by the effect of the other. To circumvent these difficulties, a low surface energy solid and true solutions or pure liquids should be used. Use of a low surface energy solid minimizes adsorption and orientation effects at the solid-liquid interfaces. By controlling s and cos 0 through use of selected pairs of pure liquids or true solutions rather than by surfactants, the adsorption effects at liquid-liquid interfaces are eliminated. In the present study TFE cores were used as the porous media. Liquids used were water, sucrose solutions, paraffin oils and benzyl, n-butyl and isobutyl alcohols. The interfacial tension was varied from 40 to 1.1 dynes/cm by suitably choosing the liquid pair. A surface active material was added to the water-oil system only in the case where interfacial tension of 0.5 dyne/ cm was desired. No precise changes of cos 0 were attempted. However, either the displaced or the displacing liquid could be made the one which preferentially wets the TFE surface. Using sucrose solutions and blends of paraffin oils proved to be a convenient way of changing the viscosity ratio between the displaced and displacing liquids. The present investigation examines the effect of interfacial tension, wettability and viscosity ratio on the immiscible liquid-liquid displacement from porous media. Observed data permit a

Jan 1, 1967

By D. A. Dahlstrom

Application of the cyclone to separation of undesirable -200-mesh clay, silt, and high-ash fractions from coal slurries was found to possess many economic and process advantages. Up to 93.3 pct removal was attained at rates of 113 to 155 gpm per sq ft of cross-sectional area.

Jan 2, 1951

By R. S. Hooper

IN attempting to describe recent mining developments at the Bunker Hill mine, it may be well to recall first the old days of hand mining when holes were laboriously drilled by hand to a maximum depth of three feet, and were shot one or two at a time, in order that the miner could take advantage of every slip, crack or bedding plane, and so save as much drilling as possible. Broken muck, of course, was loaded by hand shoveling into wheelbarrows or small cars, and heading advances or stope ton¬nages were governed by the number of men that could find room to work in any given place. The first big improvement over these old methods was the introduction of the reciprocating type of air-powered rock drill. This innovation, crude as it was, enabled the miners to set up a machine and drill a complete round of holes in one shift; but broken muck was still loaded by hand, and the size and rate of advance in headings were limited by time required to remove the broken rock. The next improvement of consequence was the appearance of the hammer-type rock drill, which greatly increased drilling speed over the reciprocating type, and made possible the completion of a full cycle in one shift, by the use of crossbars in headings, and permitted drilling and mucking to be carried on at the same time. Rock drills continued to improve as time passed, and finally the smaller and more efficient mucking machines appeared on the scene, and it became possible to muck out a round of broken rock and have a clean setup for one or more drill columns and machines. A complete cycle of mucking, drilling, and blasting was completed in one shift with an average advance of five feet. These conditions prevailed for several years, but as the mine grew deeper, the distances to transport the workers grew longer, and this fact together with the shortening of the working day, soon presented the problem of attempting to complete a cycle of operations in a shift of only six hours at the working faces. Anticipating this condition, the operating heads at the Bunker Hill had started an intensive study of more and better mechanization, and over a period of comparatively few years have adopted and placed in service methods and machines that make it possible for a three-man crew to consistently advance headings seven by nine feet in cross section, at the rate of eight feet, and more, per shift, doing all the mucking, switching, drilling and loading. These improvements consist of the following major items: I. The development of a light, flexible, easily transported jumbo equipped with pneumatic columns (Fig I), that has decreased the "setting up" and "tearing down" time an average of 1 1/2 hr per shift, or 25 pct of the available working time. These jumbos were developed at the Bunker Hill mine by members of the staff and consist of two pneumatic columns attached to a suitable carriage. They fold

Jan 1, 1947

By R. T. DeHoff, F. N. Rhines

The problem of determining the number of particles of a phase distributed randomly in unit volume c an opaque matrix from measurements made on random plane sections is closely investigated. A formalized derivation for the general case is presented. Applications of this formal result are made to specific types of aggregates dispersed in a matrix; circles, particles with flat circular ends, cylinders, and constant shape aggregates of ellipsoids of revolution. Quantitative measurements of the average geometric properties of these aggregates are developed. In 1953 R L. ullman' developed a technique for determining, from measurements made on random plane sections, the number per unit volume, Nv, of particles imbedded in an opaque matrix. Using meas urements previously developed for volume fraction, vV,' and surface area per unit volume, .SV,= he was able to determine average volume, average surface area, and average dimensions of particles, independent of size distribution, for spheres and circular disks,' as well as for uniformly sized cylinders of any axial ratio.4 The technique is mathematically rigorous for the cases studied. Recent studies of this problem have yielded rigorous solutions for the general case of cylinders, permitting evaluation of NV independent of size distribution and with all axial ratios intermixed. Generalization to shapes having flat, circular ends has been deduced. A solution has also been obtained for the ellipsoid of revolution, independent of size distribution, but requiring a constant axial ratio in the generating ellipses. In the following derivations, as in Fullman's work, it is assumed that the problem is purely a combination of geometry and probability theory,that is,eithe the particles to be measured are imbedded randomly in the matrix, or a sufficient number of random plane sections are taken to make the sample representative. A relationship exists between the number of par- ticles of a given size and shape that may be situated in unit volume (Ny) and the number of intersections a random plane can be expected to make with these particles (Na). It is the purpose of the following section to derive this relationship. The probability of Intersecting Convex Bodies. Consider a convex, closed surface, that is, one for which no two surface normals point in the same direction, situated at some arbitrary position and orientation in a cube of material that is one unit long at each edge. It is not necessary to assume that this surface is symmetrical. Let planes be constructed in the cube parallel to the top face and at random distances from it. Those planes which lie between the two planes which are just tangent to the top and bottom of the surface will intersect it. The probability that a plane will intersect the body may be defined as the limit of the fraction of planes that lie between the two tangent planes as the total number of planes constructed becomes infinite. This fraction, in the limit, is equal to the distance between the two tangent planes, DV, divided by the total length over which planes are constructed, which has been taken as unity. If the body is now rotated to a new orientation, applying the same argument, the probability of intersection is again numerically equal to the distance between tangent planes. Let DV ($, 0) be defined as the distance between tangent planes of a convex body as a function of orientation, Fig. 1. The probability, Pr, of intersecting the body with a randomly oriented and randomly positioned plane, is then equal to the average value of DV (0, $) over all possible orientations. It may be easily shown that for a system of spherical coordinates the probability of finding an orientation between Q and Q + de, $ and $ + d$ is (1/4n) sin $ dB d$, so that This relationship may be applied to each body in an aggregate of convex bodies. In particular, if the bodies in an aggregate are classified according to size and shape, and the ithsuch class is considered, Eq. 111 may be applied to this entire class, the probability of intersecting any body in this class being

Jan 1, 1962

By B. M. Larsen, T. E. Brower, J. W. Bain

A mass of circumstantial evidence is presented to indicate that the main source of alloy losses in open-hearth tapping is oxidation by air, with the steel apparently reacting with an amount of oxygen equivalent to about 30 times its own volume of air. The effect is erratic from heat to heat, depending largely on turbulence and distance of free fall of the stream of liquid metal. THIS paper reports another phase in a general study of oxidation in the open-hearth, various aspects of which have already been discussed in previous papers.1,2,3 It is based on experiments conducted on commercial, basic open-hearth furnaces at various times when opportunity offered, beginning about 1938, in an attempt to determine the mechanism and measure the amount of air oxidation during the flow of the tapping stream through the air into a ladle. This effect is closely connected, not only with alloy losses and control of chemical analysis, but possibly with various questions regarding inclusion content and steel quality and with a true picture of the deoxidation of steel in general. Thus it is believed that discussion of a large part of the results to date may be of assistance to others who are studying problems related to deoxidation or to steel cleanliness and quality. The literature reveals that strangely little attention has been devoted specifically to the effect of pouring steel through open air. Bardenheuer and Henke4 in 1939, in a paper devoted largely to overall losses of manganese in the basic open-hearth, reported that for a number of heats tapped into a tilted ladle held just beneath the runner so that the maximum distance of drop of the stream through the air was held to less than about 30 in., there was in most cases almost no loss of manganese from furnace to ladle. Hultgren,5 in 1945, showed that in high-carbon basic electric steel deoxidized in the furnace and containing no large inclusions as it left the furnace, large silicate inclusions, often rich in manganese oxide, were present in samples dipped from the pool in the ladle; also that the rise in content of large inclusions (above 0.01 mm dim) was greater when the metal stream was made to spray or flow in a turbulent manner. Our interest in this phase of oxidation in the open-hearth was first aroused by a study of alloy efficiencies on ladle additions. The frequency curves of manganese efficiency (net recovery of metal added in ladle) given in fig. 1 are of interest in this connection. Lowest, and also most variable (47 to 95 pct), recovery was in low-carbon heats having no coal additions to the ladle, progressing upward to a maximum average and least variable (82 to 97 pct) recovery in high-carbon heats killed with aluminum and silicon. Both coal additions and higher carbon contents in the tap stream, as well as additions of silicon and aluminum, help to lower the amount of manganese loss. But the most interesting point is the amount of manganese oxidized in many heats tapped at 0.50 to 1.06 pct carbon. It has been shown in a previous paper3 that the amount of oxygen in the tap stream in such heats is very small, usually below 0.01 pct, too small to oxidize any appreciable amount of manganese. Also, the fact that manganese should be oxidized at all in a metal solution containing such more stable oxide-forming elements as aluminum and silicon is an indication of some rather intense oxidizing effect such as could be caused by reaction with the air during ladle filling. Oxygen Balances from Tap Stream to Teeming Stream: Data in the form of alloy efficiencies, such as those shown in fig. 1, are not a proper measure of such a general oxidation effect. Having available

Jan 1, 1951