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By F. C. Langenberg

It is the purpose of this paper to present a limited amount of experimental data obtained on the Charpy impact machine. Several concrete examples will be given showing the relation existing between the results obtained upon the Charpy impact machine and the behavior of the parts tested when in service. Although it is pointed out by G. Charpy and A. Cornu-Thenard1 that it is first necessary to determine a satisfactory working process before studying the correlation between the results of these tests and the behavior of the parts tested in service, this ideal course cannot be strictly adhered to. If a certain part repeatedly fails in service and the available tests give no indication of its cause, advantage must be taken of any possible means that will solve the problem; therefore, even though the reliability of the results obtained by the Charpy impact machine have been questioned by many, it was necessary to use this instrument without giving careful consideration to its possible sources of error. It would seem that the conclusions arrived at by Charpy -and Cornu-Thenard justify the assumption that the precision obtained by this machine is comparable to that obtained by the other more common forms of testing. The second general conclusion arrived at by them, namely, that the impact test upon notching does not offer any direct correlation to the ordinary tests, is also borne out by many hundred determinations made in the laboratories at Watertown Arsenal. This statement, however, should be qualified as follows: Other ordinary tests include the static tensile test from bars taken in a longitudinal direction and the Brinell hardness. The author agrees that no law is yet known for the computation of the energy absorbed in the rupture of bars of the same material but of different dimensions. Although Charpy and Cofnu-Thenard do not refer in their valuable article to the use of the Charpy machine in industrial practice, it should be stated that this instrument has been in constant use in the laboratory at Watertown Arsenal for several years, and is now employed for both routine and experimental testing.

Jan 1, 1920

By Dara P. Antia, Morris Cohen, Frank S. Gardner

THERE is a conspicuous lack of information in the literature on the precise role played by residual quantities of austenite in heat-treated steels. While retained austenite may be expected to have significant effects on such important properties as the impact resistance of tools and carburized parts and the dimensional stability of dies and gauges, attempts to study these problems systematically have suffered from the absence of a reliable technique for ascertaining absolute amounts of austenite. With such a technique, not only could the relation between residual austenite and service behavior be investigated, but the chemical and heat-treatment factors that control the quantity of the austenite could also be established. Thus, the retained austenite content could then be regulated in accordance with the results desired. The presence of retained austenite may be inferred by observing the changes in properties (hardness, specific volume, electrical resistance, etc.) due to its decomposition on subatmospheric cooling1 or on tempering,2 but these indirect measurements are not readily translated into percentages of austenite. Quantitative determinations have been achieved in special cases by means of dilatometric3 and magnetic4,5 measurements; but the former procedure requires that observations be conducted during the hardening and involves difficult calibrations that limit its applicability, while the magnetic procedure is very sensitive to extraneous influences and depends upon assumptions that can only be considered as approximate in an absolute sense. Furthermore, both the dilatometric and magnetic effects are volume properties, and cannot be conveniently utilized to explore variations in retained austenite from point to point in a specimen. Some microstructures lend themselves to accurate evaluation of retained austenite contents by metallographic methods,3 but such instances are not too common, and at best, the procedure is tedious. The characteristic X-ray diffraction lines of austenite permit positive identification of its presence; and in the present paper the intensities of these lines, or the corresponding densities* on photographic film, are employed to measure the amount of the retained austenite. In order to cancel the effect of uncontrollable variations in the X-ray exposure and film-development conditions, a standard reference line is superimposed on each film by maintaining a foil of aluminum in the path of the incident X-ray beam during the entire exposure. With different samples of steel and the same foil, the ratio of the density of some one austenite line to the density of

Jan 1, 1943

By George J. Young

(San Francisco meeting, October, 1911.) THE nature of slimes handled in the treatment of gold- and silver-ores has been discussed in technical literature to a considerable extent. The subject of slime-filtration from the practical worker's stand-point has also received much comment, and scattered through the literature of the subject are descriptions of many slime-filtration installations. Articles of this nature serve a valuable purpose and assist materially in the design of new and the improvement of old plants. The subject of the physics of slime-filtration has been touched upon to only a slight extent. The underlying principles are worthy of more intensive study and experimentation than they have received, and the main purpose of this paper is to present the results of such study and experimental work as will serve to make clear in part at least many of the principles which control the filtration of slime. Nature of Slime. Much has bean written concerning an accurate definition of the term ? slime," but no comprehensive definition seems to be generally accepted. The reason for this is clear. A slime consists of at least three different substances, each, when separated, possessing distinctly different physical and to a certain extent chemical properties. These substances are extremely fine sand, a colloidal material which may be and generally is in a coagulated condition, and a colloidal material which is in a non-coagulated condition. Suspending a slime in a relatively large volume of water by shaking and allowing sedimentation to take place, results in the fine sand settling out with comparative rapidity, followed by the coagulated material, which settles much more slowly and finally a certain portion remains

Nov 1, 1911

By G. H. Lair, B. J. Langford, S. H. Rockwood

Volumetric reservoir analysis is dependent upon a firm relationship between porosity, connate water, and net pay. Capillary presswe data on core samples interrelate these three factors. It is shown that other reservoir problems may be resolved: (I) whether water production is indigenous or extraneous to the oil producing interval, (2) an oil-water contact is being approached, and (3) whether the oil-water contact is remotely situated. INTRODUCTION Volumetric analysis of carbonate reservoirs challenges the ingenuity of the reservoir engineer due to an absence of data on the minimum oil-bearing and oil-producing pores of a given reservoir rock. Many studies with this as the ultimate objective are available on the physical characteristics and fluid-flow behaviors of the carbonate reservoir. Some of these publications are: Hassler, Brunner and Deahl's1 study of the role of capillarity in oil production; Jan Law's' and A. C. Bulnes3 statistical treatment of core analysis data; Chalkley's method4,5 or estimating specific surface areas and porosity; Walter Rose's9 report on porosity, reserves, and recovery; Archie's78 tex-tural classification of carbonate rocks; Stewart and Spurlock's9 large core analysis; Purcell'sl0 mercury injection method in studying capillary pressure phenomena; Stewart, Craig, and Morse's" model multiple-phase flow test in investigating the relative permeability effect; and Fatt's12 illumi-nating network model of porous me-dia. The present study shows that the static reservoir parameters of porosity, connate water, and net productive thickness may be interrelated by utilizing a statistical arrangement of mercury capillary pressure data in addition to routine core analysis. This report summarizes the techniques that are followed to obtain these relations which are applicable to carbonate and sandstone reservoirs that do not contain clays. Capillary pressure statistical studies may be extended to include clay-bearing rocks by utilizing water capillary pressure data. POROSITY It is necessary that the laboratory determine the porosity value that includes the pores that are filled with hydrocarbons and water in the reservoir. This is the reservoir's total porosity. When true total porosity values are not available, correlations between porosity and capillary pressure characteristics lose their significance since they cannot be related through oil-base mud core data to the porosity and connate water values found in reservoirs. Methods used to obtain reliable porosity data will not be discussed; however, care should be exercised in selecting samples for measurement. In homogeneously porous formations, small core plugs sampled frequently will furnish adequate information. Where heterogeneity, particularly vugginess, is present, large-core porosity data may be required; in such reservoirs a suite of capillary pressure samples may be selected from small plugs. CAPILLARY PRESSURE Capillary pressure data provide a method for relating two carbonate reservoir parameters, porosity and connate water saturation, which in turn permit delineation of productive rock types necessary for selecting the third parameter, productive thickness. Specific applications of capillary pressure data to petroleum reservoirs were suggested by Archie8 and Pur-cell."' Their work demonstrated that in preferentially water-wet rock, porc

Jan 1, 1958

By D. R. McCord

Data of a known statistical quality has been successfully used in a system of conventional fluid mechanics equations essentially free of empirical "conformance factors to prediet early detailed field 03 in a reservoir where gravity drainage is important and oil and rock properties vary con. siderably. The system is useful where comparative recovery predictions for one or more cases of natural depletion and gas cap pressure maintenance are needed and the reservoir is not too heterogeneous. INTRODUCTION Many authors, have examined various facet* of the gravity drainage-gas cap pressure maintenance problem over the last several years. Two of them. Burtchaell and Elkins, have published practical studies. In the case described in the present paper the best development and operating plan for one of the important reservoirs of the Bolivar Coastal Field in Western Venezuela was urgently needed. It was requested that sound comparative economics be presented along with an engineering evaluation of no additional drilling, maximum drilling. several cases of gas pressure maintenance, of water flooding and combination cases. A rapid analysis of the effect on recovery of the range of crude and rock properties indicated that none of the published methods using average properties would yield adequate comparative predictions. This paper covers the predictive system developed to deal with natural depletion and gas cap pressure maintenance. The large amount of data available for this field permitted statistically reliable correlations to be made of most rock and oil properties, and the evident smooth areal variations of these properties encouraged the construction of a lineal mathematical model of material balance and fluid flow equations, which could be manipulated by a modified iterative procedure. The manipulation is much more adaptable to computing machines than manually operated calculators and subsequent studies have been prepared for the IBM Card Program Calculator. A matrix as opposed to linear model has been tentatively worked out by other members of our group to deal with more heterogeneous reservoirs. It is more adaptable to computers such as IBM-701 or the Remington-Rand Univac. In 1950, when the system reported below was developed, no rapid computing machines were available to the author. Their existence and promise encouraged an initial approach by hand. Some details of oil and rock Property correlation are included because there are a surprisingly large number of medium-sized reservoirs in the world that show systematic property variations which are significant for a rigorous analycon. All large reservoirs (over half a billion barrels recovery) with which the author is familiar contain at minimum a significant temperature variation. Using the rock and oil property correlations, past pressure and production, the gas-oil ratio history of the reservoir was computed and found to be in close agreement with field measurements. The future performance under cases of natural depletion, gas injection of 100 MMcf/day, and of 130 MMcf/day, was then computed; a 70 MMcf/day case was also carried far enough to provide data for comparative economics. The 130 MMcf/day case proved to be the most attractive. A 50,000 horsepower gas turbine driven centrifugal compressor plant to take this quantity of adjacent field gas from 30 to 1,950 psia and inject it into the reservoir is under construction. The total cost of the project will exceed 20 million dollars.

Jan 1, 1953

By R. D. Longyear

[Some Problems Involved in the Interpretation of Diamond-drill-hole Sampling and Surve ing (paper by J. J. Collins, Mining Tech., Jan. 1946). ............... I Geologic Interpretation of Magnetic Exploration on the Mesabi Range, Minnesota (paper by R. H. B. Jones, Mining Tech., July 1946) ................... 2] DISCUSSION R. D. LONGYEAR.*-Mr. Collins is to be commended very highly for the brief summary he has made of the currently used methods of taking diamond-drill sludge samples and the principles involved in evaluating the results. This paper should stimulate further discussion and research on this vitally important problem. It is particularly imperative that geologists and engineers know when assay results on sludge recovery can be accepted quantitatively and when they must be considered only qualitatively. In most cases where the sludge recovery is less than 95 per cent or more than 125 per cent, it is safest to consider the assays as of qualitative value only. Certain cases, however, are known where a relatively small proportion of the sludge sampling will give a reasonably accurate measure of the value of the total sample. One such case is ore in which the valuable mineral is of approximately the same specific gravity as the waste mineral, such as chalcopyrite in a massive pyrite body. The essential point is to determine the degree of accuracy of sludge sampling in any given drilling project and to weigh the results accordingly. It should be emphasized, however, that sludge sampling can be made reliable in many localities where careless practice produces unreliable results. In many instances, it is desirable to empty the core barrel in the core shack instead of at the drill, so that the engineer can examine the core as it first comes from the core barrel. It should be pointed out, however, that the drill * E. J. Longyear Co., Minneapolis, Minnesota. runner should be permitted to study the core to guide his future drilling. It is hoped that with the return of more normal conditions after the war geologists, engineers, contractors, and manufacturers will be able to carry on more research along the lines of improved core-barrel design and drilling technique with the objective of increasing core recovery so as to eliminate as far as possible the necessity of relying upon sludge samples. H. M. ROBERTS.*-Whoever in the future will have to do with the search for ore bodies and their exploration will have frequent occasion to refer to the clear and comprehensive summary on diamond-drilling methods by John Collins. His review of the experience of the last 40 years in this technique is invaluable. As Dr. L. D. Ricketts wrote in 1932, "The principles on which an art is founded are usually few and necessarily basic in nature, but he who wishes to achieve the power to select his aides and give success to important undertakings that may be intrusted to him in the future must ordinarily undergo years of drudgery in order to gain the experience that will enable him to distinguish such fundamentals through the haze of reinforcing detail that clothes and tends to disguise them."[t] Ricketts went on to say that since the beginning of the century there has been much

Jan 1, 1946

By R. K. McGeary, B. Lustman

The textures produced in zirconium by cold and hot rolling, and by recrystallization above and below the transformation temperature were determined. Thermal expansivities were measured in the thickness, transverse, and rolling directions of preferentially oriented zirconium and were correlated with the texture scatter in these directions. REVIOUS investigations have indicated that minor differences between hexagonal close-packed metals of similar axial ratio may appear with respect to the textures produced both on cold rolling and on subsequent recrystallization. In the case of magnesium, beryllium, and titanium, metals of axial ratio similar to that of zirconium, the ideal orientations produced by rolling are fundamentally the same, although marked variance is reported in the degree and type of scatter about the mean orientation; in those instances where recrystallization textures were observed, they were reported to be similar to the rolling textures. Measurement of the anisot-ropy of thermal expansion of both rolled and re-crystallized zirconium could not be correlated satisfactorily with the textures reported for the above metals, and therefore a study was made of the preferred orientations produced in zirconium. Reported below are the textures produced in zirconium by cold and hot rolling, and recrystallization above and below the transformation temperature, together with the results of thermal expansion measurements. Determination of Preferred Orientation Two types of zirconium were investigated: 1— "crystal bar" zirconium obtained from the Foote Mineral Co., produced by the thermal decomposition of zirconium tetraiodide, and 2—zirconium ingot obtained from the Bureau of Mines prepared by melting sponge zirconium in a graphite resistor vacuum furnace in a graphite crucible. The major impurities present in the two materials used are listed in Table I. Several of the pole figures were later checked with 0.03 pct hafnium crystal bar material and the results were identical with those to be shown for the 1.5 pct hafnium material. The materials were cold rolled to 0.014 in. in thickness as shown in Table 11. Specimens were cut from the 0.014 in. thick rolled sheets and etched to thicknesses of 0.002 to 0.010 in. Such specimens were used for exposures up to a 50' to 60" angle between the beam and plane of the specimen; for higher angles a wire shape, similar to that described by Bakarian,' was formed on an end of the original 0.014 in. sheet. A fine-bladed abrasive cut-off wheel was used to slot the sheet and to form the cylindrical cross-section. The wire shaped ends were then etched to 0.006 to 0.010 in. in diam. Although absorption of X-rays in the wire-shaped specimens does not vary with angle of rotation, the line width around the diffraction rings was not uniform, because the wire was narrower than the X-ray beam, and this condition caused some uncertainty in the estimation of azimuthal intensities. Furthermore, scanning was not practicable with this type of specimen so that spottiness of the rings due to large grain size was excessive for specimens which had been heated above about 650°C. Nevertheless, satisfactory information could be obtained for high angle exposures from the negatives by the use of both types of specimens. Transmission Laue photograms were taken using unfiltered molybdenum radiation (47.5 kv, 18 ma) and a 0.025 in. pinhole. With the film 8 cm from a 0.005 in. thick specimen exposures of about 30 min were adequate. For specimens with a coarse grain size, a device that scanned about 0.15 sq in. of sheet surface was used. An attempt was made to plot the pole figures by use of an X-ray spectrometer as described by Norton.' However, for the particular technique used, the intensity variations obtained were not considered definite enough to give reliable results, especially for the large grained recrystallized and transformed specimens. This method was therefore abandoned in favor of the standard photographic method. Nine exposures were taken of each specimen: seven exposures with the beam perpendicular to the rolling direction and at 0°, 10°, 20°, 35", 50°, 65", and 80" to the transverse direction, and two exposures with the beam perpendicular to the transverse direction and at 60" and 80" to the rolling direction. Additional exposures were then made where necessary. The intensity variations of the diffraction rings were estimated by eye. It was usually possible to estimate 3 degrees of intensity from the photograms but in some cases 2, 4, or 5 degrees were estimated. Experimental Results The preferred orientation was determined for the following treatments: 1—cold-rolled, 2—low temperature rolled, 3—cold-rolled surface layer, 4— cross-rolled, 5—hot-rolled, 6—recrystallized below the transformation temperature, and 7-—recrystallized above the transformation temperature. I—Cold-Rolled Textures: The slip plane in hexag-

Jan 1, 1952

By C. E. Turner, J. R. Elenbaas, R. D. Grimm, J. A. Vary, D. L. Katz

A technique is presented by which well samples and core plugs of dolomite formations are classified by microscopic examination into seven different porosity grades. Quantitative values of porosity and permeability are determined for each grade by a statistical correlation of the core plug test data with the porosity grading system. These quantitative values are applied directly to the grades exhibited in the well samples for the purpose of estimating the reservoir void space for wells that were not cored. The procedure is described for estimating the gas reserves per unit area lor the South Hugoton gas field. but a reserve estimate for the field is not given. INTRODUCTION The miscroscopic examination of well sample; and the graphic recording of their lithologic qualities and other distinguishing characteristics of various geologic formations drilled is both a science and an art of long standing and wide application. Usually the primary objective of a geologist who "sits on the well" and examines the samples are: to identify the formation being drilled, determine the total depth, casing point. and completion interval. In most cases the porosity is described. if done at all, in general terms. such as: trace, scattered, fine, poor, fair, medium. good, excellent, or in some other relative terms. In fields where various geologists have examined samples and recorded observations on many wells considerable variations in lithologic terms and porosity descriptions occur unless there is primary effort to establish uniformity of logging observations and standards of recording observable porosity. When an estimate of the pore volume of a reservoir is made a geologic concept of the processes that control the magnitudes of porosity and permeability is developed by microscopic examination of well samples. The characeristics and appearances are then mentally related to rather general quantitative units of porosity based on physical core data from the same reservoir or on such data or experience in other reservoirs that have similar qualities. The reliability of such estimates depends largely on the variations of the lithology of the formations, the geometric properties of its void system. the extent of comparisons of sample appearances with porosity data, as well as the uniform recording of all relevant characteristics. This statement is particularly significant for dolo-mitized limestone formations of substantial thicknesses and heterogeneity such as the Permian Dolomites of the Hugoton gas field. Jn this field, as well as in most of the Permian Dolomite fields, the producing formations are of relatively great thicknesses in which the porosity and permeability of the reservoir varies substantially in all directions, depending on the crystalline structure. degree and kind of impurities, kind of fossils anti cementation thereof, degree of dissolution. and fracturing. The variations of the lithologic texture of the dolomites and post deposition alterations have resulted in porosities and permeabilities of such magnitudes that only a part of the gross thickness can be counted as "pay." At the time of this study insufficient gas production had been experienced to apply the pressure decline production method in the South Hugoton Field and the electric logs are not definitive enough. The problem of estimating gas reserves in the south part of the Hugoton Field is primarily one of determining the pay thickness and porosity from well samples and core data. The area studied embraced all that part of the field lying south of an east-west line through Guvmon, Okla., anti containing approximately 1.000,000 acres. This paper describes a technique of correlation of physical core data with well samples so that quantitative values of pay thickness, porosity. Permeability, and connate water may be assigned to well samples that are representative of a given interval, and thereby permitting the estimation of gas reserves lor a given unit area. The procedure was developed by a uniform microscopic qualitative porosity grading of the dolo. mite core plugs.. and relating these grades to the respective physical core data on a statistical basis The well sample-were also graded in a Similar manner in order that the quantitative values established lor the core plugs could be applied to the well Sample for wells that were not cored. GRADING OF DOLOMITE A group of experienced geologists was given the assignment of examining the samples on all wells in South Hugoton in order that they could log their observations in a uniform and standardized manner and grade the observed porosity so that it could be related quantitatively to the core data. The group initiated the study 011 chips from cores which bad been tested for porosity and permeability. This study continued until all of the geologists developed a common knowledge of lithologic terms and of the characteristic appearances of the samples and their relations to measured porosity. The characteristic appearances of the dolomite samples under twelve-power magnification as related to their qualitative porosities afforded a classification of the dolomite into :even grades of porosity, ranging from dolomite of no-visible porosity under twelve-power magnification to dolomite of excellent porosity. The assigned grade for a specific 10-ft interval is a weighted average of all visible grades of porosity exhibited by the cuttings representing that interval. The porosity characteristics were recorded by a color graph adjacent to the lithology column in conjunction with a numerical system for further definition of relative porosity as shown in Fig. 1. The three vertical lines to the right of the lithology column each represent 33 1/3 per cent. which lines were used to record the percentage of the samples, for any particular interval. that showed porosity under the microscope. The colors were used to denote actual pore size. i.e., orange. blue and I-ed for pore diameter of one-fourth or less. one-fourth to one-Ilalf. and greater than one-half millimeter, respectively. The area colored 1)). one or more colors represents the percentages of the samples exhibiting pores of the respective size or sizes. The numerals from one to six inclusive shown on the log in

Jan 1, 1952

By Gerald Sherman

MINING asbestos ore by caving at Thetford Mines, Quebec, has been described in the Transactions of the Canadian Institute of Mining and Metallurgy in papers presented by the staffs of The Asbestos Corp. Ltd., in 1934, and Johnson's Co. Ltd., in 1941. The production by caving prior to 1949, in round figures, has been 14,500,000 tons of ore by The Asbestos Corp. and 5,500,000 by Johnson's Co. They are the only caving operations in asbestos at the present time. The Jeffrey mine of the Canadian Johns-Manville Co. at Asbestos, 40 miles southwest of Thetford, is well along in preparations for caving, and The Bell Asbestos Mines Ltd. at Thetford Mines, will follow their examples later. GERALD SHERMAN, Member AIME, is Consulting Engineer, Johnson's Co. and Canadian Johns-Manville Co., New York, N. Y. AIME San Francisco Meeting, Feb. 1949, and New York Meeting, Feb. 1950. TP 2828 A. Discussion (2 copies) may be sent to Transactions AIME before May 31, 1950. Manuscript received Nov. 2, 1949. Nearly all of the asbestos produced by the western hemisphere is mined in those districts of Canada. Since it has been the subject of a number of technical papers, this contribution is offered as a review of progress. Some introductory information seems appropriate, for few members of the American Institute of Mining and Metallurgical Engineers are familiar with the mineral, or how asbestos deposits differ from others in caving characteristics. Asbestos is found in peridotite, a basic intrusive rock irregularly altered to serpentine and erratically fractured, well enough to cave in bulk, but leaving many blocks of solid ore of all sizes scattered through the deposit. Chrysotile is the variety of asbestos produced in Canada. Its fibers are the most valuable commercially, having a good proportion of long fibers, strong, silky, flexible, and suitable for spinning. The fibers occur in all lengths, from the microscopic to 3 in., or more, the shorter are more abundant. Their values depend on length combined with other qualities noted above. They occur as veinlets filling fissures in the peridotite, with crystals compactly arranged in parallel across the cracks. They are sometimes lightly frozen to the walls but the partings are distinct, often marked by particles of magnetite adhering to the fiber ends. Sometimes they break away from the rock in slabs an inch or more in thickness. In wide fissures the fibers are not always continuous, the "broken fibers" being separated by lines of parting with occasional scattered grains of magnetite, which is an injurious mineral to be elirninated when possible. In addition to the chrysotile ''Cross fiber," some "slip fiber" is found in fault fractures in limited quantities of less valuable character. With the exception of the Asbestos Corp, ore, in which the content is said to be more uniform, asbestos is eccentrically distributed through the peridotite. It is the general impression that the higher grades are more often found in hard rock. There are rich pockets and leaner areas which range down through various grades to minor barren sections. Wholesale mining is necessary to make sure of recovering all the high grade for there are no reliable indications of its existence. Ore selection only appears in constructing assay-grade limits for caving. The mill yield of the Thetford ore body in 1934 was 6 to 10 pct of the ore milled, made up of all classes, with occasional runs up to 15 pct or so. Quotations for Canadian asbestos* are as follows: Per Ton No. 1 Crude (% in. and longer) $896 @ $960 No. 2 Crude (Y8 to % in.) 350 @ 545 Spinning (less than % in.) 204 @ 378 Other classes, price diminishing with length. Shorts or "refuse" 24 @ 46 • From Eng. and Min. Jnl., Nov. 1948. Asbestos of even superior quality for electric insulation is found in Arizona limestone. It is white, containing very little combined iron, but occurs only in small quantities.

Jan 1, 1951

By Gerald Sherman

MINING asbestos ore by caving at Thetford Mines, Quebec, has been described in the Transactions of the Canadian Institute of Mining and Metallurgy in papers presented by the staffs of The Asbestos Corp. Ltd., in 1934, and Johnson's Co. Ltd., in 1941. The production by caving prior to 1949, in round figures, has been 14,500,000 tons of ore by The Asbestos Corp. and 5,500,000 by Johnson's Co. They are the only caving operations in asbestos at the present time. The Jeffrey mine of the Canadian Johns-Manville Co. at Asbestos, 40 miles southwest of Thetford, is well along in preparations for caving, and The Bell Asbestos Mines Ltd. at Thetford Mines, will follow their examples later. GERALD SHERMAN, Member AIME, is Consulting Engineer, Johnson's Co. and Canadian Johns-Manville Co., New York, N. Y. AIME San Francisco Meeting, Feb. 1949, and New York Meeting, Feb. 1950. TP 2828 A. Discussion (2 copies) may be sent to Transactions AIME before May 31, 1950. Manuscript received Nov. 2, 1949. Nearly all of the asbestos produced by the western hemisphere is mined in those districts of Canada. Since it has been the subject of a number of technical papers, this contribution is offered as a review of progress. Some introductory information seems appropriate, for few members of the American Institute of Mining and Metallurgical Engineers are familiar with the mineral, or how asbestos deposits differ from others in caving characteristics. Asbestos is found in peridotite, a basic intrusive rock irregularly altered to serpentine and erratically fractured, well enough to cave in bulk, but leaving many blocks of solid ore of all sizes scattered through the deposit. Chrysotile is the variety of asbestos produced in Canada. Its fibers are the most valuable commercially, having a good proportion of long fibers, strong, silky, flexible, and suitable for spinning. The fibers occur in all lengths, from the microscopic to 3 in., or more, the shorter are more abundant. Their values depend on length combined with other qualities noted above. They occur as veinlets filling fissures in the peridotite, with crystals compactly arranged in parallel across the cracks. They are sometimes lightly frozen to the walls but the partings are distinct, often marked by particles of magnetite adhering to the fiber ends. Sometimes they break away from the rock in slabs an inch or more in thickness. In wide fissures the fibers are not always continuous, the "broken fibers" being separated by lines of parting with occasional scattered grains of magnetite, which is an injurious mineral to be elirninated when possible. In addition to the chrysotile ''Cross fiber," some "slip fiber" is found in fault fractures in limited quantities of less valuable character. With the exception of the Asbestos Corp, ore, in which the content is said to be more uniform, asbestos is eccentrically distributed through the peridotite. It is the general impression that the higher grades are more often found in hard rock. There are rich pockets and leaner areas which range down through various grades to minor barren sections. Wholesale mining is necessary to make sure of recovering all the high grade for there are no reliable indications of its existence. Ore selection only appears in constructing assay-grade limits for caving. The mill yield of the Thetford ore body in 1934 was 6 to 10 pct of the ore milled, made up of all classes, with occasional runs up to 15 pct or so. Quotations for Canadian asbestos* are as follows: Per Ton No. 1 Crude (% in. and longer) $896 @ $960 No. 2 Crude (Y8 to % in.) 350 @ 545 Spinning (less than % in.) 204 @ 378 Other classes, price diminishing with length. Shorts or "refuse" 24 @ 46 • From Eng. and Min. Jnl., Nov. 1948. Asbestos of even superior quality for electric insulation is found in Arizona limestone. It is white, containing very little combined iron, but occurs only in small quantities.

Jan 1, 1951

By T. Smales, P. L. Wright, K. Barron

The results of field measurements using an air injection technique to investigate the integrity of three pillars in the Mclntyre Mines Ltd. 114 seam at Crande Cache, Alberta, are reported. These pillars are shown to be stable and an estimate is made of the strength of these pillars. Using these results, together with Hustrulid's pillar strength formulae, a general pillar strength equation for the 114 seam is developed. This equation takes into account the probability of failure that may be deemed tolerable within the design requirements. The variation of the minimum pillar dimensions with depth below surface for uniform pillar layouts is then examined for a range of tolerable failure probabilities. A general equation of the form B = 2.60 +B Z relates the minimum pillar design width, B metres, with the overburden depth, Z metres, where B is a parameter related to the tolerable failure probability. This equation only applies for 3.05m high pillars with 6.lm wide entries. Finally, the question of what failure probability is tolerable within the design of mine pillars is discussed. This will depend on the support role required of that pillar and the anticipated period over which the pillar must perform that role. Five categories of coal mine pillars are defined, each with a somewhat different role to perform. Tentative design criteria in the form of "tolerable probabilities of failure" are suggested for four of these five categories of pillar. The fifth category of pillar has no reliable support function to perform and support must be obtained by other means.

Jan 1, 1983

By Voyle R. McFarland, Robert A. Burmeister, David A. Stevenson

The distribution of lead between phases in the Ag-Sb-Te system was studied using microautoradio -graphy. Two compositions were investigated, both containing an intermediate phase Known as silver antimony telluride as the major phase, and one containing AgzTe and the other SbzTes as the minor phase. For both compositions, two thermal treatments were used: nonequilibrium solidification from the melt and long equilibration anneals of the as-solidified structure. For each composition, lead was segregated in the minor phase of the as-solidified structure, but was distributed in the matrix after anneal. The electrical resistivity and carrier type were insensitive to the distribution of lead in the two-phase structure. ThERE has been considerable interest in the Ag-Sb-Te system because of its thermoelectric properties. The major interest has been in compositions on the vertical section between AgzTe and SbzTes, particularly the 50 mole pct SbzTes composition AgSbTez (compositions are conveniently expressed as mole percent SbzTes along the AgzTe-SbzTes section). One of the major problems in the proper evaluation and utilization of this material is the inability to control the electrical properties through impurity additions: all alloys prepared to date have been p-type, even with the addition of large amounts of impurities. It has been shown Wit all the compositions previously studied contain an intermediate phase of the NaCl st'ructure as a major phase (denoted by b) and a second phase, either AgzTe or SbzTe3, as a minor phase.'-3 One explanation for the unusual electrical behavior of this material is that the impurity additions have a higher solubility in the second phase than in the matrix; the impurity would segregate to the second phase, leaving the bulk matrix essentially free of impurity.4 In order to investigate this mechanism with a specific impurity element, the distribution of lead between the two phases was determined using autoradiography. Lead 210 was chosen because of the suitability of its 0.029 mev 0 particle for autoradiography and also because of the interest in lead as an impurity in this system.5'6 EXPERIMENTAL PROCEDURE Two compositions were taken from the vertical section between AgzTe and SbzTes, 50 mole pet SbzTes (Viz. AgSbTez) and 75 mole pct SbzTes, in which AgzTe and SbzTes appear, respectively, as the minor phase. Lead containing radioactive lead (pb210) was added to the above compositions to provide a concentration of 0.1 wt pct Pb. The material was placed in a graphite crucible in a quartz tube which was then evacuated and sealed. The samples were melted and solidified by cooling at a rate of 8°C per min and then removed and prepared for microa~toradiography. After autoradiographic examination of these samples, they were again encapsulated and annealed in an isothermal bath at 300°C for a number of days and prepared for examination. An alternate method of preparation employed a zone-melting furnace; the molten zone traversed the sample at a rate of 1.2 cm per hr and the solid was maintained at a temperature of 500°C both before and after solidification. This treatment had the same effect as solidification at a slow rate followed by an anneal for several hours at 500°C. In order to obtain the best resolution, thin sections of the alloy were prepared by hand lapping to a thickness of approximately 20 p. Other samples were prepared for examination by lapping a flat surface on the bulk sample. The resolution, although somewhat better in the former procedure, was adequate in both instances and the majority of the samples were treated in the latter fashion. A piece of autoradiographic film (Kodak Experimental SP 764 Autoradiographic Permeable Base Safety Stripping Film) was stripped from its backing, care being taken to avoid fogging due to static-electrical discharge. A small amount of water was placed on the sample, the film applied emulsion side down on the surface of the sample, and the sample and the film dipped into water in order to assure smooth contact. After drying, the film was exposed for 2 to 5 days, the period of time selected to give the best resolution. The film was developed on the specimen and fixed and washed in place. Two major factors must be considered in establishing the reliability of an autoradiograph: the in-

Jan 1, 1964

By D. W. G. White

The surface tension of zinc has been determined by the sessile-drop method in a progvam emphaszzing detailed experimental care. The surface tension oj. the pure metal was measured over a range of ternperature from the melting point (419.6"C) to 540°C. At the melting point, the suvface tension of zinc was found to be: 1) 99.99+ pct Zn - 757.0 5 dynes per cm 2) 99.999+ pct Zn - 761.0 5 dynes per CI 3) 99.9999 pct Zn - 76'7.5 5 dynes pev cna From experiments carried out in a closed, isothermal cell, the temperatuve coejyicient of the surface tension (6y/6T)p, , of zinc xas found not to be negative but to be postiue. A positive tenzperatre coefficient indicates a greater depee of order in the surface than in the body of the lquid. Houlezer, by delibevately inducing continuous zaporization, a temperature coefficient of su)face tension with a negative slope can be produced. The work reported herein was undertaken as part of a larger program of fundamental research on the properties of molten zinc and zinc alloys. This program grew out of a continuing interest at the Mines Branch in the behavior of liquid metals in the foundry and of a desire on the part of the zinc industry for reliable basic data. The work was originally begun in cooperation with the Consolidated Mining and Smelting Co. Ltd., Trail, B.C., and was subsequently continued from 1960 to date in association with the Canadian Zinc and Lead Research Committee and the International Lead and Zinc Research Organization. Although the surface tension of liquid zinc has of course, been measured before, as Table I and Fig. 1 demonstrate, there is not good agreement among the existing values. Such disparities arise because sources of experimental error are insufficiently controlled. This situation places the reader in doubt. One result may be correct within narrow limits—even fortuitously—yet, because there is not agreement between several values, none can be accepted with conviction and all become suspect. It seemed, therefore, in the circumstances, that there was room for further work embodying considerable emphasis on experimental care in order that, within a small margin of error, an accurate value might be obtained. It was in this spirit that the work was undertaken. METHOD The sessile-drop method -as adopted for this work. In this method, when applied to liquid metals at elevated temperatures, the outline of the meridional section through a drop resting freely on a horizontal surface is recorded photographically. Certain parameters

Jan 1, 1967

By T. W. Guy

THE increased moisture due to water¬spraying for coal dust control is of interest even for mines from which the coal is to be wet-washed before screening, because in many cases wet coal dust materially decreases the loading efficiency of men an equipment at the faces. It also causes serious increase in the normal wear and deterioration of all equipment with which it comes in contact. It is important to the consumer if it increases his as-receive moisture. No attempt will be made in this paper t cover the entire subject of water-spraying of coal for dust control. It will be confine to discussion and data on (r) percentages c dust in bituminous coals, (2) moisture increases due to spraying for dust control in mines or plants by methods which have proven satisfactory for periods of one to five or more years, and (3) a few suggestions for research. SIZE AND PERCENTAGE OF COAL DUST The U. S. Bureau of Mines1 classifies a coal dust all bituminous coal passing 20-mesh sieve (0.0328 in. square opening; The percentage of such dust to be found is ROM coal, of course, varies widely wit. the characteristics of the seam, and with the methods used in the mining and in the preparation of the coal. ROM screen analyses of 12 U. S. coals selected at random from personal files given in Table I show: A few other screen analyses examined indicating 40 pct or more of 2o-mesh X o dust in 3/8 in. X o-sizes were not included because of uncertainty that they were representative. The number of results in Table I is not sufficient to give a reliable estimate of the average, or of the range to be expected, but it indicates that in every case the coal dust is a relatively large percentage of the total ROM coal, and, of course, a progressively larger percentage of resultants as the larger sizes are separated for marketing.

Jan 1, 1948

By Richard W. Markley

A centralized online data acquisition system has been developed by the U.S. Bureau of Mines Pittsburgh Mining and Safety Research Center for rapidly digitizing, storing, and processing experimental signals originating up to 1100 feet away from a central computer. This system, which services seven laboratories, is currently based on a CDC System 17 1/- computer with 56K of semiconductor memory, four disk drives (one shared online with a CDC 1700), two magnetic tape drives, high-speed A/D hardware, and other input/output peripherals. The laboratories are linked to the central computer by 15-pair cables and signal conditioners and to the computer's communications controller by modems and current loops. The A/D throughput rate is approximately 30,000 samples per second (9 bit plus sign resolution) and permits scanning about 30 instruments once every millisecond for up to 100 seconds, being limited only by disk capacity. The laboratories serviced by this facility conduct explosions research and include such facilities as an Experimental Coal Mine Explosion Facility (45 channels), a Constant Volume Combustion Laboratory (4 channels), and a Simulated Coal Mine Laboratory (15 channels). Personnel support includes one systems analyst, two applications analysts, one operator, and a hardware technician. The system has performed adequately for burst-type data acquisition, but due to a lack of long-term reliability (24 hours) of the real-time multiprogramming operating system and unpredictable power failures, slow phenomena signals are generally digitized and stored offline. This latter data is input to the computer through peripherals such as a high-speed paper tape reader, or high-speed asynchronous communications ports. Processing of data is done either in real-time (as soon as data is collected) or in batch mode. Smaller batch jobs are run on this computer, and all others are transmitted by means of the system's high-speed UT 200 terminal simulator to a CDC-6000 series computer.

Jan 1, 1977

By C. E. Violet, R. J. Borg, E. M. Howard

The miscibility gap in the Au-Ni system has been determined by Mossbauer spectroscopy, with used as a probe. The phase boundaries were determined from the compositional dependence of both the isomer shift and Curie temperature. X-ray diffraction measurements were also used to confirm the Mossbauer results. 1 HE purpose of this research is to demonstrate the application of Mbssbauer spectroscopy to the determination of phase boundaries and to redetermine the miscibility gap by an independent and novel technique. The techniques evolved in this study are readily applicable to other polyphase systems and are generally as quick and accurate as the more conventional methods, e.g., metallography, X-ray diffraction, thermal analysis, and so forth. To be sure, not all polyphase systems will lend themselves favorably to Mijssbauer investigations, but this is a problem met in the use of conventional methods as well. The Mbssbauer spectrum responds to a different set of physical parameters, and consequently provides an entirely independent method of analysis. It is especially useful if the system has either a ferromagnetic or an antiferromagnetic transition. The Au-Ni system was selected because alloys containing more than -60 at. pct Ni become magnetically ordered at low temperatures; also the miscibility gap is quite well established (see Ref. 7 for a compilation of pertinent references, also Fig. 11, and thus provides a reliable test of this novel procedure. As Fe is the most commonly used Mijssbauer isotope, there exists a wealth of information concerning its behavior in iron-containing alloys and compounds. However, as yet there have been relatively few experiments using it as a probe to investigate nonferrous systems. By choosing a nonferrous alloy system, we are able to demonstrate that its use is not restricted to systems containing iron as one of the major constituents. Wertheim and ~ernick' have used the same method to investigate Cu-Ni, and demonstrated that one can obtain a systematic variation in the isomer shift and magnetic hyperfine field. However, we believe this to be the first time these techniques have been used to establish phase boundaries. Two hyperfine interactions were measured and used to determine the phase boundaries, viz., the magnetic hyperfine splitting and the isomer shift which in this alloy system are both strong functions of composition. Calibration curves were established based upon single-phase solid solutions obtained by quenching from temperatures well above the maximum of the miscibility gap, see Fig. 1. Solid solutions containing 25, 50, 65, 75, 85, 92, and 96 pct Ni as well as pure nickel were used in the calibration procedure. Fig. 2 shows the Curie temperature, TC, and the isomer shift, v,, as determined from the Mbssbauer spectra, and variation in lattice parameter as determined by X-ray diffraction, as functions of composition. The compositions of the two-phase systems quenched from temperatures within the miscibility gap are obtained by comparing their respective values of TC and v0 with the calibration data. I) EXPERIMENTAL Mbssbauer sources were made by fusing the component metals in a tungsten arc melter, which has a water-cooled copper hearth. Both nickel and gold were 99.999 pct pure, and the melting was done in an atmosphere of purified argon. The alloys were rolled, diced,

Jan 1, 1969

By Takashi Katsura, Avnulf Muan

Equilibrium relations in the system FeO-Fe2O3 Cr2O3 have been determined at 1300°C at oxygen pressures ranging from that of air (0.21 atm) to 1.5 x 10-11 atm. The following oxide phases have stable equilibrium existence under these conditions : a sesquioxide solid solution with corundum-type structure (approximate composition Fe2O3-Cr2O3); a ternary solid solution with spinel-type structure (approximate composition FeO Fe2O3-FeO Cr2O3) and a ternary wüstite solid solution with periclase-type structure and compositions approaching FeO. The metal phase occurring in equilibrium with oxide phase(s) at the lowest oxygen pressures used in the present investigation is almost pure iron. The extent of solid-solution areas and the location of oxygen isobars have been determined. ThE system Fe-Cr-O has attracted a great deal of interest among metallurgists as well as ceramists and geochemists. Metallurgists have studied the system because of its importance in deoxidation equilibria, ceramists because of its importance in basic brick technology, and geochemists because of its importance for an understanding of natural chromite deposits. Chen and chipman1 investigated the Cr-O equilibrium in liquid iron at 1595°C in atmospheres of known oxygen pressures (controlled H2O/H2 ratios). The main purpose of their work was to determine the stability range of the iron-chromite phase. Hilty et al.2 studied oxide phases in equilibrium with liquid Fe-Cr alloys at 1550°, 1600°, and 1650°C. They reported the existence of two previously unknown oxide phases, one a distorted spinel with composition intermediate between FeO Cr203 and Cr3O4, the other Cr3O4 with tetragonal structure. They also sketched diagrams showing the inferred liqui-dus surface and the inferred 1600°C isothermal section for the system Fe-Cr-O. Koch et al3 studied oxide inclusions in Fe-Cr alloys and also observed the distorted spinel phase reported by Hilty et al. Richards and white4 as well as Woodhouse and White5 investigated spinel-sesquioxide equilibria in the system Fe-Cr-O in air in the temperature range of 1420" to 1650°C, and Muan and Somiya6 delineated approximate phase relations in the system in air from 1400" to 2050°C. The present study was carried out at a constant temperature of 1300° C and at oxygen pressures ranging from 0.21 atm (air) to 1.5 x 10-11 atm. The chosen temperature is high enough to permit equilibrium to be attained within a reasonable period of time within most composition areas of the system, and still low enough to permit use of experimental methods which give highly accurate and reliable results. These methods are described in detail in the following. I) EXPERIMENTAL METHODS 1) General Procedures. Two different experimental methods were used in the present investigation: quenching and thermogravimetry. In the quenching method, oxide samples were heated at chosen temperature and chosen oxygen pressure until equilibrium was attained among gas and condensed phases. The samples were then quenched rapidly to room temperature and the phases present determined by X-ray and microscopic examination. Total compositions were determined by chemical analysis after quenching. In the thermogravimetric method, pellets of oxide mixtures were suspended by a thin platinum wire from one beam of an analytical balance, and the weight changes were recorded as a function of oxygen pressure at constant temperature. The data thus obtained were used to locate oxygen isobars. The courses of the latter curves reflect changes in phase assemblages and serve to supplement the observations made by the quenching technique. 2) Materials. Analytical-grade Fe2O3 and Cr2O3 were used as starting materials. Each oxide was first heated separately in air at 1000°C for several hours. Mixtures of desired ratios of the two oxides were then prepared. Each mixture was finely ground and mixed, and heated at 1250" to 1300°C in air for 2 hr, ground and mixed again and heated at the same temperature for 5 to 24 hr, depending on the Cr2O3 content of the mixture. A homogeneous sesquioxide solid solution between the two end members resulted from this treatment. A Part of some of the sesquioxide samples thus prepared was heated for 2 to 3 hr at 1300°C and oxygen pressures of 10-7 or 1.5 x 10-11 atm. Reduced samples (either iron chromite

Jan 1, 1964

By Thomas T., Read

E DUCATION for the mineral industry was at first a single comprehensive curriculum, but it was early recognized that the main basis of mining is physics, while that of metallurgy is chemistry. The first school to offer curricula leading to degrees in mineral industry education in the United States (1853) had separate ones in mining and metallurgy. The Columbia School of Mines (the first really successful one) had only a single curriculum when it opened in 1864, but within a few years had so reorganized its work that it offered curricula in mining, metallurgy, geology, chemistry, and civil engineering. Interest in the metallurgy or geology curricula was slight at first, and for the next 30 years the great majority of Columbia students took the mining curriculum, probably partly because it contained nearly as much geology as the geology curriculum, practically all the metallurgy, and most of the chemistry, and partly because of the degree awarded for it. Other schools kept their mining curricula equally broad, and as late as 1900-1910 men were graduating as mining engineers who were practically as well prepared to make geology or metallurgy their life work, as they were for mining. Gradually, however, the subject matter of mining geology and metallurgy became so enriched through research and development that separate curricula in them became worth while; their progressive development is the subject of another chapter. Mining curricula also began to be somewhat diversified, and schools in areas where coal mining was of outstanding importance began to offer options in coal mining, the earlier curricula having been chiefly aimed at metal mining. The petroleum industry began its meteoric rise about the same time as mineral instruction in this country, but little more of applied science attended its birth than had attended such ancient practical arts as copper and iron

Jan 1, 1941

New York Meets first Wednesday after first Tuesday of each month. J. E. JOHNSON, JR., Chairman EDGAR RICKARD, Vice-Chairman D. M LIDDELL, Secretary, 7 Wall St., New. York, N. Y C. A. BOHN, Treasurer JOHN V. N. DORR _ LEWIS W FRANCIS Boston Meets first Monday of each winter month. R. L. AGASSIZ, Chairman - JAMES G. CARLETON, Vice-Chairman E. E. BUGBEE Secretary-Treasurer, Mass. Inst. of Technology, Cambridge, Mass. W. E. C. EUSTIS G. A. PACKARD Columbia Holds four sessions during year. Annual meeting in September or October. S. S. FOWLER, Chairman J. C. HAAS, Vice-Chairman LYNDON K. ARMSTRONG, Secretary-Treasurer. P. O. Drawer 2154, Spokane, Wash. W. H. LINNEY

Jan 2, 1918

By A. V. Bradshaw, R. I. L. Guthrie

The behavior of large bubbles in the size range 4 to 25 cm3, rising through molten silver, has been studied. It was found that rising velocities were equivalent to those in aqueous systems of low viscosity. Mass transfer coefficients for oxygen bubbles dissolving in silver were found to be 0.036 ± 0.007 cm sec-1, being close to those predicted for transfer through the front surface of the spherical cap bubble only. It is suggested that the surface active nature of oxygen in silver could account for the relatively low coefficients obtained. MANY metallurgical processes involve interactions between gas bubbles and liquids. Examples include the removal of carbon monoxide in Open Hearth Steelmak-ing, the removal of sulfur by blowing air through copper matte during converting, and the removal of hydrogen from steel during vacuum degassing or inert gas flushing. The steps involved in such refining processes include; transport of the dissolved species to the bubble interface, adsorption and chemical reaction of the species at the interface, desorption of product molecules from the interface, and transport of product gas into the bulk gas phase of the bubble. It has been concluded1 that all the interfacial steps involved proceed so rapidly at steelmaking temperatures that transport of the solutes, present in the metal, become the important rate controlling factors provided nucleation phenomena are not restrictive. The O-Ag system was chosen for the investigation into gas bubble-molten metal interactions due to the relatively high solubility of oxygen that enables rates of oxygen transfer to be measured from changes in bubble volume. Other advantages of this system include the absence of a stable oxide phase at an oxygen pressure of 1 atm and the relatively low melting point of the metal which permits the use of a metallic container, providing that it is resistant to oxidation. In those metallurgical processes where bubbles have an important influence, bubble volumes are usually greater than 5 cm3. For this reason the present study relates specifically to single large bubbles of oxygen rising in silver. These bubbles adopt the characteristic spherical cap shape similar to that shown in Fig. 1 for a 30 cc bubble rising in water. After an initial investigation to determine the velocities of inert (nitrogen) bubbles rising in molten silver, experiments were carried out with oxygen and the rates of mass transfer between the oxygen bubbles and the silver were measured. EXPERIMENTAL Apparatus. The apparatus, Fig. 2, for containing molten silver, was constructed from "Nimonic 75" Alloy (75 pet Ni, 20 pet Cr, 5 pet Fe, Mn) and provided for the release of single bubbles from an hemispherical cup, situated at the bottom of the column. The cup was turned by translating the rotation of the drive shaft through 90 deg. This was accomplished by the use of a bevelled gear system, and a smooth drive was provided by the lubricating action of the silver on the gears. Since reliable high temperature seals at 1000°C were found to be impracticable, the filling and drive shaft tubes were extended outside the 3.5 kw resistance wire tube furnace, where connections were made using easily accessible O-ring seals. The apparatus remained gas tight to the atmosphere at pressure differentials far in excess of those used. The filling tube was connected via a small bore tube to the differential pressure transducer. Gas could be bubbled into the inverted cup from two i-in. tubes which passed down the inside of the column to preheat the gas. The temperature of the silver was maintained at 1020°C during all experiments. Measurement of Bubble Volume. In order to calculate mass transfer rates, it was necessary to obtain a continuous record of the bubble's volume during its passage through the column of molten silver. The method adopted for measuring the bubble volume involved closing off the top gas space to the atmosphere prior to each experiment, and recording the variation in gage pressure of this space during the formation and rise of the bubble. Since any change in bubble volume results in an equal change in top space volume, Boyles Gas Law may be applied (for isothermal con-

Jan 1, 1970