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By E. D. Gardner

IN 1947 the metal-mining industry . passed through a year of readjustment; catching up on development work has caused production to suffer. Skilled labor has been short in most mining districts, notwithstanding the highest wage rate paid in the history of the industry. The trend has continued toward increased mechanization and refinements in practices and methods to increase the tons produced per man-shift. Improvements in procedures, however, have not kept pace with rising labor rates; and, in general, labor costs per ton mined have steadily increased since the war years. Prices of base metals have been the highest in a generation, but most producing companies can afford to pay the high wages. Capital expenditures have been approved for improvements to increase the output per man, both to reduce unit labor costs and to increase output. Surveys indicate a continuing

Jan 1, 1948

By E. H. Crabtree

IN an ideal mill, with perfect milling operations, the mineral extraction would be 100 per cent, the, concentrate would be 100 per cent mineral, the tailing would assay zer.0 mineral and the milling cost would be zero dollars. Such an operation can, of course, never be attained. We can only strive to approach it as nearly as possible and in doing so most recognize .the fact that the three primary factors in milling: assay of concentrate, assay of tailing, and cost of operation bear a definite economic relationship to each other. This relation will change from time to time and will be different for different mills, depending on milling equipment, character and quality of feed, market conditions, and other factors. It is granted that for a given operation there is an economic point, but the location of this point is difficult. It is for the purpose of making some of these economic points a little more tangible that this paper has been prepared.

Jan 1, 1930

By Josiah Royce

To evaluate chemically the sample of rock obtained by diamond drilling, it has long been recognized that the analyses of the two components of the sample, core and sludge, must be given appropriate influence in computing the average analysis of any unit of depth. The purpose of this investigation is to set forth what means are available for apportioning the effect of core and sludge on the final analysis, what variables affect the problem, and what combination of applied mathematics will closest approximate the truth under each condition as these variables proceed within their limitations. A drill hole is bored in iron ore ex- ploration principally to test variations in rock composition with depth and is usually directed as nearly normal to the bedding of a horizon to be tested as possible. This practice has a tendency to minimize variation in composi- tion laterally which in any event is not likely to be great. It is obvious that the opportunity for change in analysis of a particular rock is not statistically as great radially in a diamond drill hole where the distance in which such a change may occur is from 0.719 in. (EX bit) to 1.469 in. (NX bit) as there would be longitudinally even in a run as short as 5 ft. Variations in composition of bedded or layered rocks are usually greater normal to the bedding than parallel thereto. Even in massive rocks, like porphyries, varia- tions are functions of distance. Hence, in either case, variations along the hole are of greater effect than across it.

Jan 1, 1949

By Walter E. Lewis

Myriad problems face all of us in the next decade. Vietnam, poverty, and pollution are perhaps the most pres- sing. A lesser one but still vital to us as a Nation is the slow hut apparently relentless extinction of the mining, metallurgical. geological and petroleum engineer. Are we doomed to take our place in the crossword puzzle with the moa. to be defined like it as an "extinct bird"? Or can we reverse the trend perhaps, in the next decade? The plain fact is we are an endangered species, and must resign ourselves to virtual extinction in the 1970's unless the trend is reversed. Probably, many of us have felt the problem will solve itself if left in the in-basket long enough, believing, that the trend will reverse solely on the basis of demand for these disciplines. This approach has not worked up to now, it gives no promise of working in the future, and furthermore, the problem has been in the in-basket much too long. The point is simply this: What can each of us do as an individual, or as part of a company, a State agency, a Federal agency, a university, or an organization such as AIME?

Jan 1, 1970

By S. C. Jones, J. A. Davis

This paper describes displacement mechanisms of micel-lur solution slugs, displuced by a thickened water "mobility buffer", in a glass micromodel and in consolidated Berea sandstone cores. Colored motion pictures, taken through a microscope, recorded interactions on a pore-to-pore bash in the micromodel. Production and differential pressure data from consolidated cores previously waterflooded to residua1 oil saturation revealed displacement mechani.sm.s macroscopically. Oil is displaced miscibly, while interstitia1 water is displaced immiscibly by the injected micellar. solution slug. Part of this water is dispersed and carried near the lead ing edge of the .slug, and some may remain as a residual saturation. Thickened water displaces any residual water. It also emulsifies with the. slug material, thereby displacing it. The displacement sequence forms banks of oil and water with relatively constant fractional flows, saturations, and mobilities. The mobility of oil and water flowing ahead of the .slug defines .slug viscosity required for stable displacement. Equations are presented that describe. several aspecis of the displacement flow behavior: oil breakthrough, oil cut during production of the stabilized bank, breakthrough of banked water and the resulting decreased fractional flow of oil, fluid mobilities, etc. Breakthroughs, calculated from the equations, are compared with experimental data. Slugs of micellar sollution, ranging from 1 to 5 percent PV, produced unusually high oil recoveries (up to 100 percent) in previously waterflooded consolidated cores. Investigation of the effect of mobility buffer size on oil recovery indicated that recovery is reduced in 3-in. X 4-ft cores for mobility buffer sizes .smaller than 50 percent of the pore volume. Introduction A new oil recovery process,* conceived in 1962, utilizes a slug of micellar solution' that has sufficient viscosity to avoid an unfavorable mobility ratio with respect to the oil and water it displaces. These micellar solutions are composed of hydrocarbons, water, and surfactants, and may contain electrolytes and co-surfactants. The micellar solution is displaced by a "mobility buffer". The mobility buffer is a bank of reduced-mobility fluid, preferably an aqueous polymer solution. The entire system is displaced by unthickened water. This paper describes some of the microscopic and macroscopic displacement mechanisms observed during laboratory development of the fluids for a potential field test. Microscopic phenomena were observed photographically in a specially constructed glass flow model and macroscopic data were taken from constant rate, tertiary displacements conducted in Berea sandstone cores. Qualitative Description of Micellar Solution Flooding This section qualitatively describes displacement mechanisms that occur when a slug of micellar solution is injected into a previously waterflooded core. The slug completely removes oil from the portion of core it contacts, and banks oil in the process. The oil saturation in this bank and the flowing WOR reach definite, fixed values that are determined by water and oil mobilities and slug characteristics. This zone of constant WOR and oil saturation will be called "stabilized oil bank" in the following discussion. When this stabilized bank reaches the outlet end of the core, the oil cut jumps from zero to a constant value equal to the fractional flow of oil. Saline water has little or no solubility in the slug. Because of this. the slug displaces in-place brine immiscibly. During slug injection, most of the brine is displaced ahead of the slug, some is carried along in the leading portion of the slug, and part of the brine may become immobile. The immobile, residual brine is later miscibly displaced by thickened water. Displacement of all the oil and only part of the water during slug injection results in a higher fractional flow of oil ahead of the slug than occurs when all the water is displaced after injection of thickened water is begun. The slug spontaneously emulsifies fresh (low-salt content) water. By emulsification, the slug can become infinitely diluted, and hence totally displaced, by thickened water. Fluid saturations in the core are shown schematically in Fig. 1. Parts A and B show conditions before and after the start of the thickened-water injection, respectively. Since thickened water displaces any residual brine by-

Jan 1, 1969

By AIME AIME

AT the Morenci branch of the Phelps Dodge Corporation, of which Frank Ayer is manager, several new types of machines that have been developed by Charles Mitchell, shop foreman in the drill steel shop, invite comment for their time and labor-saving qualities. Foremost of these is an adjustable gage-block and gaging device for attachment to drill-sharpening machines, developed and patent applied for by Mr. Mitchell. It replaces the blocks on the standard Ingersoll-Leyner drill steel sharpener No. 5. Features of the device are gage blocks with a flat surface which can readily be removed when worn and planed in any flat planer; blocks that can be adjusted with a templet to give a far more accurate gage than was formerly possible; and a center stop that is adjustable and can be accurately set to center any standard size drill steel.

Jan 1, 1930

By Paul F. Kerr

The insufficiencies of our mineral resources are becoming well known, and the national political conscience seems to be troubled at last by our dependence upon mineral commodities which must come from other lands. This realization places increased responsibility upon the industrial, educational, and governmental groups whose task it will be to solve the problems of mineral supply. As we all know, from the time that man first sought mineral deposits until recent years, prospectors have been largely responsible for mineral discoveries. Today the era of the prospector is almost over. The human ants that have literally examined all accessible outcrops and have tested the gravels of nearly all stream beds in the United States have left undiscovered few worthwhile mineral deposits within the scope of their recognition. The pages in the history of mineral exploration are now being turned from the era of the surface prospect to the era of the hidden de- posit.

Jan 1, 1949

CONTENTS PAGE BARTON, D. C.-The Eötvös Torsion Balance Method of mapping Geologic Structure (T. P. No. 50) 1 GEORGE, P. W.-Experiments with Eötvös Torsion Balance in the Tri-State Zinc and Lead District (T. P. No. 65). 15 LANCASTER-JONES, E.-The Computation of Eötvös Gravity Effects (T. P. No.75) HEILAND, C. A.-A Cartographic Correction for the Eötvös Torsion Balance-(T. P. No. 52) 17 SLICHTER; L. B.-Certain Aspects of Magnetic Surveying (T. P. No. 120). . . . 18 WEAVER, W.-Certain Applications of the Surface Potential Method (T. P. No.121) LUNDBERG, H.-Recent Results in Electrical Prospecting for Ore (T. P. No. 98). . 20 HOTCHKISS, W. 0., ROONEY, W. J. and FISHER, J.-Earth-resistivity Measure-ments in the Lake Superior Copper Country (T. P. No. 82) 21 LEONARDON, E. G. and KELLY, S. F.-Some Applications of Potential Methods to Structural Studies (T. P. No. 115) 23 MASON, M.-Geophysical Exploration for Ores (T. P. No. 45) 25 The Eötvös. Torsion Balance Method of Mapping Geologic Structure Discussion of the paper of D. C.. Barton, issued as Technical Publication No. 50 with Mining and, Metallurgy, February, 1928. D. C. BARTON.-The field surveys which I have been privileged to use as illustrations for this paper were done for Mr. DeGolyer's companies and were released through his favor. W. J. MILLARD, Tulsa, Okla.-Has any oil been found by the torsion balance in West Texas? D. C. BARTON.-NO new oilfield has been discovered on the basis of torsion balance work. It has had some part in controlling the policy of certain companies in playing the extension of known oil fields. A number of "T. B." structures have been drilled and dry holes obtained. Of those known to the writer, one apparently was a structural high, one is a broad general high but locally low and probably is a deep-seated structural high, one seems normal although the control is poor, and one was considered structurally low but is now suspected by some geologists of being structurally high. E. L. DEGOLYER, New York, N. Y.-A large gravity structure, generally referred to, I believe, as the Crosby County Structure, has been found in West Texas. This structure is perfectly symmetrical with the arrows all pointing toward a common center, very much like the Nash salt-dome pattern in Dr. Barton's paper (Fig. 9). One of the peculiar things about it, from the standpoint of the gravity high, is that it is so

Jan 1, 1928

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 AIME

THE wind howls almost incessantly over the mining engineers working in the near desert that is the Division of Namaqualand, the upper Atlantic coastal corner of South Africa's Cape of Good Hope Province. But when these men at the U. S.-owned mines called Nababeep South and East O'okiep (pronounced Oh-keep) tell you about their achievements, they can be heard above the wind. For their O'okiep Copper Co. Ltd. now produces over half the Union of South Africa's annual output of 30,000 tons of copper metal. Moreover, it is a very decent sample of U. S. geotechnical imagination. financial daring, and managerial skill, all operating successfully in a

Jan 1, 1947

By D. C. Sisti

A technical evaluation of actual performance of the preparation facilities at Beaver Consolidated Coal Co.'s Stinson plant is presented, with special emphasis on sulfur reduction in 1-1/2 x 3/8 in., 3/8 in. x 28 mesh, and 28 mesh x 0 size fractions. Evaluation of the heavy medium section of the plant and the treatment of the 28 mesh x 0 coal is included. Design criteria considered for sizing and selection of equipment required to process 1-3/4 million tpy of raw coal on coals of divergent washability characteristics are summarized.

Jan 1, 1976

By AIME AIME

CHARLIE WARNER, Chairman of the Petroleum Division, is no stranger to the problems of the oil industry or to those of the Petroleum Division, after more than 25 years of experience in locating and producing oil and more than 22 years of membership in the Institute. He was born at Jefferson, N. Y.. April 27, 1894, and educated in the public schools of New York State and at Cornell University where he studied geology and allied sciences from 1913 to 1917 and received a B.A. degree. Immediately upon completion of this training, he was employed by the Empire Gas & Fuel Co. as a field geologist in Oklahoma and Kansas. Two years later he became district geologist for the Emerald Oil Co. in Oklahoma and Kansas, and in 1920 he rejoined the Empire Gas & Fuel Co. in the capacity of district geologist in Oklahoma. In September of 1921 he began his association with the Houston Oil Co. of Texas. He was district manager for the company in the Mid-Continent area until 1932 when he was transferred to the head office at Houston, where he became superintendent of the land and lease department in 1934 and was elected a director of the company in 1941. In these capacities, and also as petroleum engineer for the company, he keeps in intimate touch with all phases of field activity and with the regulation of the industry by State and Federal agencies.

Jan 1, 1943

By Cyril Wells, Robert F. Mehl

The diffusion of carbon in gamma iron plays an essential role in many metallurgical processes. In carburizing, in graphitizing, in homogenizing, in the formation of pearlite from austenite, and in other processes, migration of carbon in gamma iron occurs.1'2 A full understanding of the rate at which these processes occur obviously requires a knowledge of the rate of diffusion of carbon. In carburizing, for example, the depth of carbon pentration is determined by the carbon concentration in solid solution at the surface, and by the rate of diffusion inward of the carbon. Until reliable data on the rates of diffusion of carbon are available it is unlikely that a full quantitative description of this process will be obtained. In the formation of pearlite from austenite, the segregation of carbon and alpha iron from the austenite obviously requires the diffusion of carbon; the rate at which pearlite nodules grow is evidently controlled at least in part by the rate of diffusion of carbon; it is unlikely that we shall understand the factors that determine the rate of growth unless data on rates of diffusion of carbon, and the variation of these with composition, grain size, and temperature are available. Accordingly it was decided: (1) to determine, more accurately than hitherto, the diffusion coefficients of carbon in austenite over a wide temperature and a wide concentration range, (2) to study the influence of grain size and impurities on this diffusion coefficient, and (3) to study the effect of manganese and nickel on the rate of diffusion of carbon in the austenite of manganese and nickel steels, respectively; the influence of carbon on the rate of diffusion of manganese and of nickel will be made the subject of later papers. The rate of diffusion of carbon in gamma iron has been studied by Runge3 by Tammann and Schonert4, by Bramley and co-authors,5-14 and

Jan 1, 1940

By Cyril Wells, Robert F. Mehl

The diffusion of carbon in gamma iron plays an essential role in many metallurgical processes. In carburizing, in graphitizing, in homogenizing, in the formation of pearlite from austenite, and in other processes, migration of carbon in gamma iron occurs.1'2 A full understanding of the rate at which these processes occur obviously requires a knowledge of the rate of diffusion of carbon. In carburizing, for example, the depth of carbon pentration is determined by the carbon concentration in solid solution at the surface, and by the rate of diffusion inward of the carbon. Until reliable data on the rates of diffusion of carbon are available it is unlikely that a full quantitative description of this process will be obtained. In the formation of pearlite from austenite, the segregation of carbon and alpha iron from the austenite obviously requires the diffusion of carbon; the rate at which pearlite nodules grow is evidently controlled at least in part by the rate of diffusion of carbon; it is unlikely that we shall understand the factors that determine the rate of growth unless data on rates of diffusion of carbon, and the variation of these with composition, grain size, and temperature are available. Accordingly it was decided: (1) to determine, more accurately than hitherto, the diffusion coefficients of carbon in austenite over a wide temperature and a wide concentration range, (2) to study the influence of grain size and impurities on this diffusion coefficient, and (3) to study the effect of manganese and nickel on the rate of diffusion of carbon in the austenite of manganese and nickel steels, respectively; the influence of carbon on the rate of diffusion of manganese and of nickel will be made the subject of later papers. The rate of diffusion of carbon in gamma iron has been studied by Runge3 by Tammann and Schonert4, by Bramley and co-authors,5-14 and

Jan 1, 1940

By Alexander N. Mitinsky

UP to a certain limit, the increase of pressure on the diamond-drill increases the rate of progress in drilling. That limit is set by the resistance of the diamonds to compression; and beyond it, the destruction of the stones will involve an. economic loss, both in time and in money. It is, therefore, important to all diamond-drillers to know what is the resistance mentioned. In Europe, operators usually follow an empirical rule, which directs the maintenance of a pressure, on the area-of the bottom of the drilling-tool, of 12 kg. per sq. 4m. For the tools in ordinary use, this is equivalent to 1 kg. per sq. mm. of the diamonds set in the tool So far as I know, American drillers are using pressures as high as 50 to 60 kg. per sq. cm. of the total area of the drill, and the consumption of diamonds (on Denny's authority, 0.2 carats per meter bored) is greater in America than in Europe. But the reason for this difference may be the comparatively larger size of the diamonds commonly used by American drillers. With the assistance of my friend, the late S. Woisslaw, who was the pioneer of diamond-drilling in Russia, I selected from his stock a number of black diamonds, which I subjected in my laboratory to compression-tests. To prepare regular cubes for such tests, as is generally done with other stones, would have been not only costly, but, what is more important, practically useless. I therefore determined, in order to assimilate as nearly as possible the conditions of actual use, to place each sample between a hard plate (corresponding to the rock) and a softer plate (corresponding to the bottom of the tool), into which it would be pressed during the test.

Jan 1, 1906

By P. A. Robbins

FAR NORTH, on the bare Arctic tundra, 11 mi. above the mouth of the Keewalik River where the latter discharges into Kotzebue Sound. several ., Eskimos garbed in parkies and muck lucks mingle with a small group of similarly clad white men. All of them shield their eyes from the white glare of the arc as a gasoline-driven arc-welding set rains molecules of metal on the break in a bull wheel, the large gear wheel which swings the boom and cab of a dragline shovel.

Jan 1, 1937

By F. W. Lee

A GREAT CURTAILMENT of field activities among the geophysicists occurred last year, especially in prospecting for the common metals. In gold, however, an "outstanding achievement . . . was made by the engineers of Consolidated Goldfields. Here the suboutcrop of the Main Reef Series was traced from Middelvlei through properties of the westward area, a distance of from 30 to 40 miles. Here Drs. Reineche and Krahman prospected with the aid of a sensitive magnetometer and established the singularities of the various beds which heretofore had not been sufficiently appreciated. Several underlying shale beds were used to determine this suboutcrop under the dolomite. This area promises to be the equivalent of one-half the size of the present gold fields and to rank in value with the Far East Rand." The present temperature compensated magnetometers permit accurate field observations to less than 5 gammas. Since magnetic anomalies may have their origin due to a change of elevation as well as to the outcropping of a bed of another magnetically different material, intimate geological knowledge is of great assistance in the interpretation of these measurements. To what extent magnetic measurements reflect the basement when the material is homogeneous, consisting primarily of red granite, was determined by members of the Bureau of Mines and described by Dr. J. H. Swartz. Because of the diverse causes of magnetic anomalies, some of which were discussed and correlated by Stratton and Joyce upon known conditions, magnetometer measurements are often difficult to interpret.

Jan 1, 1933

By T. M. Morris

G. L. Simard and D. J. Salley—The authors and ourselves" independently came to similar conclusions both as to the value of tracer methods for the study of flotation and the general nature of collector-mineral interaction. The dodecylamine-quartz system appears to be simpler than the dithiophosphate-galena one, and the results therefore appear clearer. It is evident from a comparison of the two papers, however, that care must be used in extending the results to other more complicated systems. In the case of dodecylamine-quartz, the possible influence of micelle formation is of interest. There is no a priori reason why complete monolayer formation should necessarily occur at the concentration for micelle formation, since sorption depends on the nature of the substrate as well as on the properties of the solute in solution which alone determine micelle formation. Indeed, the fact that the onset of increased adsorption, point B in fig. 2, occurs at a concentration one tenth the critical value for micelles might imply that micelle formation does not have an influence. Interestingly enough, the data may be handled by the methods used for multilayer adsorption of gases on surfaces. Thus, if the amount adsorbed is plotted versus concentration, a sigmoid type curve is obtained, similar in form to a so-called Type I1 isotherm13 generally attributed to multimolecular adsorption. A monolayer value of about 0.12 mg per g may be estimated from the knee of this isotherm. On the other hand, if a plot is made according to the multilayer gas equation for adsorption to an unrestricted number of layers, eq 38,13 assuming the critical micelle concentration as the saturation concentration, the data above 120 mg per liter fall on a straight line from which a monolayer adsorption of 0.3 mg per g results. These considerations suggest that the monolayer may occupy an area somewhat less than the geometric value of 0.4 mg per g, and that micelle formation may indeed be a factor in the adsorption. the angle between the solid-liquid and liquid-gas interfaces, measured through the liquid. The value of the equilibrium contact-angle is uniquely determined by the value of the interfacial energies of the three intersecting interfaces and is independent of other forces in the system. When the liquid-gas interface intersects the solid at an edge—as was the case for all the experiments reported in this paper—the orientation of the solid-liquid interface is indeterminate or varies through 90" for a right-angle edge. Mr. Morris has called the angle between the horizontal and the liquid-gas interface for this edge condition a "static contact-angle." I feel that this term is unnecessarily misleading. In the first place, "static contact-angle" sounds too much like "equilibrium contact-angle." In the second place, the magnitude of the "static contact-angle," which I would prefer to call the "supporting angle," is determined by the forces in the system other than those derived from the interfacial energies, hence "contact angle" is misleading. If Mr. Morris had said that the "supporting-angle" is variable and depends on the weight of the particle and size of the bubble and that it has a maximum possible value equal to the equilibrium contact-angle, his discussion would have been more accurate. T. M. Morris (author's reply)—Mr. Kellogg puts forth a reasonable criticism of some of the terminology used in the paper. I agree that the term "static contact angle" may be misleading. Substitution of the term "supporting angle" or "vector angle" may be more suitable. F. X. Tartaron—In this paper the author presents a very interesting mathematical development of the forces present when a mineral particle adheres to an air bubble. Excellent concordance is obtained between mathematical formulation and experimental results. It is the writer's understanding that when the mineral surface presented to an air bubble is greater than the area of contact, the maximum contact angle is obtained. However, this contact angle represents distortion of the bubble, the normal shape of which is spherical or in cross-section, circular. This distortion produces a force that acts in opposition to the force of adhesion between the bubble and particle. Hence, at maximum contact angle, the force of adhesion between bubble and particle is at a minimum for static conditions. However, when the size of bubble is increased, the size of particle remaining the same (and all other conditions remaining the same), the contact angle decreases, the distortion of the bubble decreases and the force in opposition to adherence of bubble and particle also decreases. Thus, there is stronger attachment between bubble and particle. When this situation is applied to actual flotation conditions, it is doubtful that it has any significance. The reason is that the bubbles are normally so much larger than the particles, that in substantially all cases, it is probable that negligible distortion of the bubble takes place. In table IV, the author makes computations for bubbles from 0.50 to 2 mm diam. This is from 0.02 in. to 0.08 in. Certainly the bubbles generated in a flotation machine are far larger than this. The surfaces of the author's bubbles range from 0.79 to 12.6 sq mm. The area of contact of the glass rod (0.15 mm diam) is 0.017 sq mm. Thus, ratio of bubble surface to mineral area of contact ranges from 47 to 741 in round numbers. If we take a %-in. diam bubble and a 65-mesh (0.208 mm) particle of cubical shape, the ratio of bubble surface to mineral area of contact is 2931. Mineral particles do not readily become attached to air bubbles. Taggart has shown that in pneumatic flotation machines collector-coated particles are only temporarily attached to bubbles. They keep falling off and down in the froth but at a delayed rate as compared with gangue. Spedden and Hannan's motion pictures confirm the difficulty of attaching particles to air bubbles. In the agitation froth process, according to Taggart, air is precipitated from the water selectively on to the collector-coated particles and these

Jan 1, 1951

By T. M. Morris

G. L. Simard and D. J. Salley—The authors and ourselves" independently came to similar conclusions both as to the value of tracer methods for the study of flotation and the general nature of collector-mineral interaction. The dodecylamine-quartz system appears to be simpler than the dithiophosphate-galena one, and the results therefore appear clearer. It is evident from a comparison of the two papers, however, that care must be used in extending the results to other more complicated systems. In the case of dodecylamine-quartz, the possible influence of micelle formation is of interest. There is no a priori reason why complete monolayer formation should necessarily occur at the concentration for micelle formation, since sorption depends on the nature of the substrate as well as on the properties of the solute in solution which alone determine micelle formation. Indeed, the fact that the onset of increased adsorption, point B in fig. 2, occurs at a concentration one tenth the critical value for micelles might imply that micelle formation does not have an influence. Interestingly enough, the data may be handled by the methods used for multilayer adsorption of gases on surfaces. Thus, if the amount adsorbed is plotted versus concentration, a sigmoid type curve is obtained, similar in form to a so-called Type I1 isotherm13 generally attributed to multimolecular adsorption. A monolayer value of about 0.12 mg per g may be estimated from the knee of this isotherm. On the other hand, if a plot is made according to the multilayer gas equation for adsorption to an unrestricted number of layers, eq 38,13 assuming the critical micelle concentration as the saturation concentration, the data above 120 mg per liter fall on a straight line from which a monolayer adsorption of 0.3 mg per g results. These considerations suggest that the monolayer may occupy an area somewhat less than the geometric value of 0.4 mg per g, and that micelle formation may indeed be a factor in the adsorption. the angle between the solid-liquid and liquid-gas interfaces, measured through the liquid. The value of the equilibrium contact-angle is uniquely determined by the value of the interfacial energies of the three intersecting interfaces and is independent of other forces in the system. When the liquid-gas interface intersects the solid at an edge—as was the case for all the experiments reported in this paper—the orientation of the solid-liquid interface is indeterminate or varies through 90" for a right-angle edge. Mr. Morris has called the angle between the horizontal and the liquid-gas interface for this edge condition a "static contact-angle." I feel that this term is unnecessarily misleading. In the first place, "static contact-angle" sounds too much like "equilibrium contact-angle." In the second place, the magnitude of the "static contact-angle," which I would prefer to call the "supporting angle," is determined by the forces in the system other than those derived from the interfacial energies, hence "contact angle" is misleading. If Mr. Morris had said that the "supporting-angle" is variable and depends on the weight of the particle and size of the bubble and that it has a maximum possible value equal to the equilibrium contact-angle, his discussion would have been more accurate. T. M. Morris (author's reply)—Mr. Kellogg puts forth a reasonable criticism of some of the terminology used in the paper. I agree that the term "static contact angle" may be misleading. Substitution of the term "supporting angle" or "vector angle" may be more suitable. F. X. Tartaron—In this paper the author presents a very interesting mathematical development of the forces present when a mineral particle adheres to an air bubble. Excellent concordance is obtained between mathematical formulation and experimental results. It is the writer's understanding that when the mineral surface presented to an air bubble is greater than the area of contact, the maximum contact angle is obtained. However, this contact angle represents distortion of the bubble, the normal shape of which is spherical or in cross-section, circular. This distortion produces a force that acts in opposition to the force of adhesion between the bubble and particle. Hence, at maximum contact angle, the force of adhesion between bubble and particle is at a minimum for static conditions. However, when the size of bubble is increased, the size of particle remaining the same (and all other conditions remaining the same), the contact angle decreases, the distortion of the bubble decreases and the force in opposition to adherence of bubble and particle also decreases. Thus, there is stronger attachment between bubble and particle. When this situation is applied to actual flotation conditions, it is doubtful that it has any significance. The reason is that the bubbles are normally so much larger than the particles, that in substantially all cases, it is probable that negligible distortion of the bubble takes place. In table IV, the author makes computations for bubbles from 0.50 to 2 mm diam. This is from 0.02 in. to 0.08 in. Certainly the bubbles generated in a flotation machine are far larger than this. The surfaces of the author's bubbles range from 0.79 to 12.6 sq mm. The area of contact of the glass rod (0.15 mm diam) is 0.017 sq mm. Thus, ratio of bubble surface to mineral area of contact ranges from 47 to 741 in round numbers. If we take a %-in. diam bubble and a 65-mesh (0.208 mm) particle of cubical shape, the ratio of bubble surface to mineral area of contact is 2931. Mineral particles do not readily become attached to air bubbles. Taggart has shown that in pneumatic flotation machines collector-coated particles are only temporarily attached to bubbles. They keep falling off and down in the froth but at a delayed rate as compared with gangue. Spedden and Hannan's motion pictures confirm the difficulty of attaching particles to air bubbles. In the agitation froth process, according to Taggart, air is precipitated from the water selectively on to the collector-coated particles and these

Jan 1, 1951

By R. W., Ludt

THE use of froth flotation for the separation of minerals has become one of the most important of ore dressing processes. Its particular adaptability to the enrichment of low grade ores has made the process an important factor in the national economy. The methods have been extended to the recovery of a great number of minerals. Among the few minerals which have resisted efforts toward industrial flotation is chrysocolla, a hydrated partly colloidal copper silicate. Chrysocolla, being a product of natural oxidation, has been found to occur in small quantities with many ores which are recovered by flotation methods. In present practice, these small quantities of copper silicate pass off with the tailings and are lost. The advantages to be gained by a satisfactory process for the recovery of chrysocolla is apparent. Any application of principles which points a way toward the satisfactory industrial flotation process for copper silicate would be of advantage. This paper presents an attack on this problem.

Jan 1, 1949