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A MINING institute open to all men interested in any branch of the mining industry will be held at the Col-lege of Mines, University of Washington, Seattle, during the week beginning March 5. Prospectors, miners, mine owners, persons interested in metallurgy, investors in min-ing enterprises, and the public generally are invited to at-tend. This institute will take the place of the Winter Min-ing Session which originated at Seattle in 1897 and con-tinued for twenty-eight years. The complete new equip-ment of the Mines Laboratory will be used to give demon-strations of new machines and processes of mining, ore dressing, and metallurgy. This year the ceramic industry, including cement and branches of clay working of special Importance in the Northwest, will be included in the insti-tute. All instruction will be given by specialists. Prominent technical men and managers will give lectures on their special subjects. Among the speakers engaged are G. T. Jackson, formerly superintendent of the Alaska-Gas-tineau and the Chichagof mines, who will speak on the mining of large bodies of low-grade ore; R. F. McElvenny, superintendent of the Tacoma Smelter, on the nature of contracts that a smelter can offer to mines and prospects; M. D. Leehey, mining lawyer, on some popular errors re-garding the mining law; H. H. Townsend, on the explora-tion and purchase of prospects by operating companies; J. L. McAllen, on quartz mining in the Willow Creek dis-trict, Alaska; F. Powell, on gold dredging. In the evenings, lectures illustrated by stereopticon views and moving pic-tures will be given. The week will close with an excursion o mines and plants.

Jan 3, 1928

By Eugene McAuliffe

THE Coal Division undertook its most ambitious program this year at the New York meeting, with six full' sessions and a luncheon on Monday which had a record attendance and at which the newly elected officers for the Division were announced. Eugene McAuliffe, president of the Union Pacific Coal Co., Omaha, Neb., was unanimously selected as Chairman; J. B. Morrow, preparation manager of the Pittsburgh Coal Co., as Vice-Chairman; and H. E. Nold, Ohio State University, Secretary. During the past year two new and interesting activities were conducted by the Division directed at stimulating the interest of junior and student members. Reports were presented at the luncheon meeting by the chairmen of these commit¬tees. J. B. Morrow. chairman of the paper prize awards, and H. N. Eavenson reported on the work of the mining machinery manufacturers fellowship, the work on which was completed the first of the year. Several excellent papers are expected from these two groups for the next meeting of the Division to be held in Pittsburgh some time in the fall. The regular six-session program was filled from start to finish with interesting papers and much discussion, but unfortunately not enough time for the latter. The papers covered the field of prospecting, mining methods, preparation, utilization, mechanization, and safety, and all through the program we were constantly reminded of the value and need of research in the coal industry.

Jan 1, 1936

By R. Buehl

ALTHOUGH the main features of the transformations occurring in 18-8 have been published already,1-4 certain conclusions merit questioning and discussion. The questions may be summarized as follows: PERCENT REDUCTION BY COLD ROLLING FIG. 1.-VARIATION OF FERRITIC INDUCTION AND PERCENTAGE OF FERRITE WITH COLD REDUCTION. Composition of Alloy: C, 0.08; Mn, 0.40; Si, 0.24; P, 0.014; Cr, 18.13; Ni, 8.94. 1. If ferrite is formed by cold-working austenite, what happens to the carbon with which the ferrite and austenite are both pre-sumably supersaturated? 2. What is the nature of the alpha-ferrite formed at grain boundaries by chromium-carbide precipitation at these boundaries?

Jan 1, 1939

By R. P. Alger, C. A. Doh, M. P. Tixier

The principle, the equipment and field operation of sonic logging are described. The tfio-receiver system produces logs independent of hole size and mud. Field experience is given and forms the basis for the interpretation of the log. The derivaiion of porosity values from measured velocities is discussed, according to the type of formations (hard formations, compacted sands, and unconsolidated formations). The time-average equation proposed by M. R. J. Wyllie, A. R. Gregory and L. W. Gardner is uscd as a basis for the computation of porosity in limestones, cemented sandstones and compacted sands. Variations in the lithologic character of limestones do not seem to change the porosity calibration markedly. The compaction of sands is related to the compaction of shale adjacent to them; and, thus, the shale velocity is used for the establishtnent of empirical relations for the computation of porosity in un-consolidated formations. Various forrnu.las are tentatively presented to account for shale and fluid content. Field experience demonstrates that considerable attenuation of sonic energy takes place in unconsolidated formations, particularly when gas bearing, and in fractrured formations. Unusually large attenuation produces skipped cycles, a feature easily recognized. The application of sonic logging to structura1 studies is featured, showing its possible integration with the dipmeter. Correlation and its application to the irrterpretation of seisrmic surveys are reviewed. The paper is illustrated with field examples. Sonic logging is the recording of the time required for a sound wave to traverse a definite length of formation. Sonic travel-times are inversely proportional to the speed of sound in the various formations. The speed of sound in subsurface formations depends upon the elastic properties of the rock matrix, the porosity of the formations and their fluid content and pressure. Below the "weathered" or low-velocity layer extending from 50 to 100 ft or so below the surface, sound velocities may range from about 6,000 ft/sec in shallow shales to as much as 34,000 ft/sec in dolomites. In hard formations (well cemented and/or compacted), the sonic log reflects the amount of fluid in the formations; hence, it correlates well with their porosity. In unconsolidated formations, which are usually of fairly high porosity, the sonic log gives an approach to porosity determination, when its readings are corrected for lack of compaction, shaliness, and fluid content. In such formations the sonic log may also indicate the presence of gas and may distinguish between oil- and water-bearing beds. Field experience with the sonic log in soft formations is more limited than that in hard formations. As a result, interpretation in soft formations is not as well developed at the present time. In all types of formations the sonic log is of considerable value for correlation and for the more detailed and accurate interpretation of seismic data. EQUIPMENT AND PRINCIPLE FIELD OPERATION The basic features of the sonic log" are a two-receiver system and two available short spacings. The log is recorded on film using a standard field unit. An SP curve is run along with the sonic curve to give a more interpretable log and to establish absclute depth control for comparison with other logs run in the same well. If desired, a gamma-ray curve may be recorded simultaneously with the sonic curve. Fig. 1 shows the sonic-gamma ray combination sonde. The sonic portion consists of a sound transmitter and three receivers mounted 3, 4 and 6 ft from the transmitter. When the first and second receivers are used, a sonic log of I -ft spacing (distance between receivers) is obtainea. Use of the first and third receivers provides a 3-ft spacing. The transmitter emits pulses at the rate of l0/sec. After the transmission of a pulse the first arrival of sound energy at each receiver triggers its response system. The differ-

By N. J. Grant, Per Knudsen, J. T. Blucher

The fatigue behavior of three SAP alloys was studied in ternzs of strain rate and temperature, at high strains. The k values in the modified Manson-Coffin equation, Nk4 = C, were less than 0.5 under all test conditions, and change with strain amplitude for the lower-oxide alloys at about 2 pct strain. Lowest k values were near 0.25. Strain rate had no effect on life at 80 F, but had an increasingly greater effect with increasing temperature above 500". Life decreased with decreasing strain rate, above 500"F, and with increasing temperature. Ductility at fracture in a tension test was indicated to be an important factor in determining 1ife in these big+-strain tests with the SAP alloys. INEVITABLY, in the course of mechanical tests at elevated temperatures, particularly if significant time at temperature is involved, there are large changes in structure; these changes make it difficult to relate behavior patterns over ranges of temperature or strain rates at high temperatures. Such changes are to be expetted in low cycle fatigue at low strain rates and high temperatures. Accordingly, it was of great interest to examine the low cycle fatigue behavior of SAP / an aluminum oxide dispersion-strengthened aluminum, a type of alloy which had shown unusual structure stability to temperatures as high as 1000" to 1150°F and resisted recrys-tallization essentially to the melting temperature.'j3 Since the matrix is pure aluminum, there are no complications of averaging, agglomeration, or phase solution. It was also desirable to check the Manson-Coffin equation4?' for the SAP alloys, namely N~E~ = , where ep is the total plastic strain amplitude, k and C are constants, and N is the number of cycles to failure. Here, too, was an opportunity to check the roles of temperature and strain rate with a very stable material. Tavernelli and coffin6 had concluded that k had a value of about 0.5 for many alloys and C was equal to ~/2, where E is the fracture ductility determined from a static tension test. The results were obtained from low-temperature tests where creep and diffusion processes are unimportant. Manson7 found k = 0.6 fitted his data reasonably well; however, in later analyses of a large amount of low cycle fatigue data generated at room temperat~re@"~ he found k to vary from 0.6 for short lives to 0.21 for long-life fatigue tests. In the latter studies,89g Manson separated the total strain range into elastic and plastic components when he found that k was influenced by the nature of the strain. The use of EL (total strain) instead of EP (total plastic strain)4'5 makes a difference in the resultant k value. The ratio of changes with temperature, strain rate, and strain; further, there are the problems in the determination of the elastic strain. Based on these considerations, and the improved fit of points in a plot of by Wells and Sullivan,' is also utilized in these studies. Anderson and wahl,14 using commercial 1100 aluminum, and Blucher and Grant,15 using 99.99 pct pure aluminum, found an increase in life with increasing test temperature. Anderson and Wahl were the first to report low cycle fatigue results from SAP materials. With increasing temperature, the role of strain rate becomes more important. In this regard, care must be exercised to differentiate between frequency (wherein strain rate may vary from zero to a maximum in each cycle, sinusoidally, for example), and constant strain rate, as used in the present study, in a saw-tooth type cycle; in the latter case, the frequency is not specified but can easily be calculated from the strain and strain rate data. It has generally been found that life in low cycle fatigue tests decreases with decreasing frequency16 or with decreasing strain rate at elevated temperatures.15 Coffin,17 reviewing Eckel's work,16 also reported that k increased with decreasing frequency for acid lead, yielding values from 4.0 at a frequency fo 6.6 cycles Per day to 1-46 at a frequency of 7440 cycles per day; the value of k decreased to 0.58 at a frequency of 2.38 x lo6 cycles per day. EXPERIMENTAL PROCEDURE Three SAP alloys, of two nominal compositions, were tested. Alcoa supplied XAP 005 as 2-in.-diam extruded bar, of nominal composition A1-7 wt pct A1203. The Danish Atomic Energy Commission supplied SAP 930 (A1-7 wt ~ct Ala3) and SAP 865 (A1-13 wt pct Al&) manufactured by Swiss Aluminium Ltd., in the form Of $-in.-diam extruded rod. Metallographic comparison of the structures of XAP 005 and SAP 930 showed the former to have a more uniform oxide distribution. Button-head specimens were machined in the longitudinal direction of the bar with 0.4 in. gage length by 0.2 in. diameter, with a fillet radius of j-B in. After machining, the specimens were electropolished in a 1 to 4 mixture of perchloric acid to methanol to remove all machining marks. All test bars were in the as-extruded condition. The fatigue tests were performed on a hydraulically activated, axial strain machine, with complete reversal of strain.15 Test conditions were:

Jan 1, 1969

By J. C. Scully, G. Sanderson

The electrolytic formation of y hydride in thin foils of Ti-5Al-Z.5Sn alloy and four Ti-A1 binary alloys has been studied by electron microscopy and electron diffraction. Two orientation relationships have been found: THE adsorption of hydrogen by titanium alloys from aqueous solutions has been widely reported. This can occur, for example, in both alkaline' and acidic2 pickling baths, in chemical polishing374 and electro-polishing Solutions,3,4 during cathodic polarization5" and under certain corrosion conditions,7,8 Etching reagents may also produce visible precipitates, sometimes after an aging period.9 During an investigation into the stress corrosion susceptibility of a titanium alloys by thin foil electron microscopy many observations have been made of hydride precipitation which has been deliberately promoted by techniques that are described below. The characteristics of hydride precipitation are reported and the observed crystallographic orientation relationships are discussed with reference to distortion in the titanium lattice created by the presence of the hydride. EXPERIMENTAL TECHNIQUE One grade of commercial titanium and five alloys were examined. Their composition and hardness values are shown in Table I. All the materials were in the form of thin sheet, 0.05 to 0.065 cm thick, which had been annealed after cold rolling. Foils suitable for transmission electron microscopy were made in two ways: a) by chemical polishing; and b) by elec-tropolishing. The solution used for chemical polishing was a mixture of 44 pct HF and 73 pct HNO3 in the volumetric ratio 2:3. During this polishing specimens were manually moved up and down in the solution. The reaction was veFy rapid, specimens thinning to foil thickness (2000A) in 5 min. Since chemical polishing solutions tend not to cause hydride contamination if they are kept cool3 no attempt was made to prevent the solution from becoming hot during the thinning operation. Electropolishing was performed at -30° C with a mixture3 composed of 295 cu cm methyl alcohol, 175 cu cm n-butyl alcohol, and 30 cu cm perchloric acid with an applied voltage of 40 v after chemically thinning specimens to approximately 0.017 cm thickness in a cool solution of 44 pct HF, 40 vol H2O2, and water in the volumetric ratio 1:6:3. EXPERIMENTAL RESULTS 1) Ti-5A1-2.5Sn Alloy. The Ti-5A1-2.5Sn alloy was severely contaminated by hydrogen during the chemical polishing. Foils obtained in this way contained large amounts of the y hydride phase. A typical micrograph is shown in Fig. l. The laths were identified as the hydride phase by selected-area diffraction of a large number of foils examined in a tilting stage that could be turned through 40 deg. Using the lattice spac-ings of the alloy obtained by X-ray diffraction as a standard the a value of the hydride was determined fromo the electron diffraction patterns to be 4.38 to 4.40A. The accuracy of this figure is only about ±2 pct. Further evidence of the identification was obtained by vacuum annealing chemically polished foils of the alloy at 500°C. This resulted in the dissociation of the hydride with the production of dislocations and possibly vacancy loops as shown in Fig. 2. The hydride

Jan 1, 1968

By James F. Kemp

Discussion of the paper of D. Foster Hewett, Bulletin To. 27, March, 1909, pp. 291 to 310. JAMES F. KEMP, New York, N. Y.:-Mr. Hewett's paper is one of exceptional interest, because it not only adds an important contribution regarding one of the rarer, valuable elements, but also because it introduces compounds hitherto unknown and in associations no less novel. While we have occasionally dis¬covered and recorded asphaltite in metalliferous deposits, for example in the Joplin and Granby districts, we have not seen a metallic ore in a deposit essentially asphaltite. The source and method of introduction afford a subject well worth serious reflection. Vanadium was first discovered and recognized as a distinct element in the slags obtained in smelting the titaniferous magnetites at Taberg, Sweden. For a long time, therefore, we looked upon the titaniferous magnetites as its hone. Analyses proved, years ago, that it was present in the ores of this type in New Jersey and in the Adirondacks. It was quite rarely determined, but when looked for it was, I think, invariably found, although the Amount seldom exceeded 0.5 per cent. of V,05., In just what combination it exists in the titaniferous ores is uncertain. One might imagine V2O3 replacing some of the Fe2O3 of magnetite; or, since in the lead series vanadates and phosphates are closely akin, one might wonder if a lime-vanadate could take the place of apatite. Yet no lime-vanadate has been found in nature, and apatite itself is usually rare in the titaniferous ores. When percentage-curves are plotted for a series of analyses of the ores, the line of vanadic oxide shows a curious sympathetic behavior with the line of chromic oxide;' but the data are somewhat limited, and no compound has sug¬gested itself which throws light on the matter. Dr. W. F. Hillebrand has discussed the occurrence and dis-

Oct 1, 1909

By B. E. Field

COBALT is a silvery white metal with a slight bluish cast, strongly resembling nickel in its appearance and properties, notably its resistance to corrosion, although its alloys with other metals differ quite decidedly in their properties from those of nickel. The name cobalt was derived from the German "Kobold" meaning goblin and this came to be applied to the cobalt minerals which, although they resembled ores, did not readily yield metal when smelted by the primitive processes available in the Middle Ages. Cobalt minerals were used as pigments by potters and glass workers before the Christian era. Cobalt blue glass was found in the tombs of the Egyptians and in the ruins of Troy, and many colors used by the ancient Greeks and Romans contained cobalt. The ancients were entirely unaware that the colors they used were caused by cobalt and the metal itself was only isolated about the middle of the eighteenth century by Brandt although the preparation of cobalt compounds had been carried on in a small way ever since the opening of the silver-cobalt deposits at Schneeberg, Germany, in 1470. The metal is fairly hard, with a density when pure of 8.81 in the cast state and 8.92 after working. The com¬mercial grade of cobalt has a density of about 8.75 in the cast state. The atomic weight is 58.97. The Brinell hardness of the pure metal is 124; that of the commercial grade varies from as low as 100 to as high as 138, depending upon the impurities present. Pure cobalt has a sharp melting point at 1478°C. The tensile strength of the pure metal in the cast condition is said to be higher than that of any other pure metal. Kalmus gives it as 34,400 lb. per sq. in. for cast unannealed metal; the effect of annealing at 850 to 900°C. is to raise the strength slightly. The yield point is close to the ultimate strength and the reduction in area and elongation are both low. Mechanical working raises the tensile strength of pure cobalt rapidly and in the form of wire it will be over 100,000 lb. per sq. in. The presence of small quantities of carbon in the commercial metal raises the tensile strength to as high as 61,000 lb. per sq. in., the reduction in area and elongation being raised at the same time to approximately 20 per cent.

Jan 1, 1933

By L. L. Davis

Current research by the US Bureau of Mines to develop technology for improving efficiency and productivity in metal/nonmetal mines is described. The research program addresses a wide variety of problems associated with each of the major categories of mining: underground mining, surface mining, m situ mining, and premining investigations. An overview of the Bureau's research activities is given with emphasis on underground mining. In particular, two innovative and promising concepts currently under development are described: a unique shaft sinking system that uses an impact hammer for rock fragmentation, and a low-profile portable crusher for underground hard-rock applications.

Jan 1, 1982

By E. I. Larsen, E. F. Swazy, F. R. Hensel

Experience has indicated that hard bronzes are not suitable for bearing applications where high bearing loads and speeds are involved. It is the general practice to utilize softer materials for these purposes, such as copper, lead, silver, babbitt, lead-base alloys, and more recently aluminum-base alloys, preferably supported by a steel backing. It was the objective of the present investigation to study a new material produced by powder metallurgical methods susceptible to precipitation-hardening. Test MAteriaIs Preliminary tests were made with compacts containing copper, nickel and silicon in quantities sufficient to form 3 to 5 per cent nickel silicide. It mas found that this type of alloy was susceptible to the formation of a soft surface shell when sintered in tank hydrogen. The depth of the shell depended On the length of sintering time and sintering temperature, and varied in thickness from a few thousandths to as much as One eighth inch. This soft shell resulted from the preferential oxidation of silicon, thereby reducing the efficiency of age-hardening by the nickel silicide compound. The body of the sintered compacts below the soft shell could be precipitation-hardened to a hardness of 70 to 85 Rockwell B, by quenching from goo°C. and age-hardening at 450°C. A series of tests was made with various addition agents, in order to decrease the rate of preferential oxidation, and it was found that phosphorus was most beneficial in this respect. After considerable experimentation, the following nominal com-position was accepted as standard: 2.4 per cent nickel; 0.8 silicon; 0.3 phosphorus; balance copper. The physical propertties and certain bearing properties of this alloy are described in the present paper Preparation of Compacts Several methods of incorporating the hardening ingredient (nickel silicide) were studied. Compacts formed from copper, nickel and silicon powders were found to be inferior to those fabricated from prealloyed nickel silicide master alloys, because of the rapid oxidation of pure silicon during sintering. The use of a prealloyed nickel silicide hardener containing 25 per cent silicon and 75 per cent nickel could be further improved by preparing a master alloy, incorporating nickel, silicon, phosphorus and copper, having the following nominal composition~ 25 per cent nickel; 7 silicon; 3 phosphorus 64 copper. This alloy is brittle in the cast condition and can be readily powdered. Sintering Procedure The blended powders were pressed at '5 to 40 tons per sq' in., the pressure depending on the size and shape of the compacts. Sintering was carried out in hydrogen or cracked ammonia atmospheres at

Jan 1, 1946

By E. I. Larsen, E. F. Swazy, F. R. Hensel

Experience has indicated that hard bronzes are not suitable for bearing applications where high bearing loads and speeds are involved. It is the general practice to utilize softer materials for these purposes, such as copper, lead, silver, babbitt, lead-base alloys, and more recently aluminum-base alloys, preferably supported by a steel backing. It was the objective of the present investigation to study a new material produced by powder metallurgical methods susceptible to precipitation-hardening. Test MAteriaIs Preliminary tests were made with compacts containing copper, nickel and silicon in quantities sufficient to form 3 to 5 per cent nickel silicide. It mas found that this type of alloy was susceptible to the formation of a soft surface shell when sintered in tank hydrogen. The depth of the shell depended On the length of sintering time and sintering temperature, and varied in thickness from a few thousandths to as much as One eighth inch. This soft shell resulted from the preferential oxidation of silicon, thereby reducing the efficiency of age-hardening by the nickel silicide compound. The body of the sintered compacts below the soft shell could be precipitation-hardened to a hardness of 70 to 85 Rockwell B, by quenching from goo°C. and age-hardening at 450°C. A series of tests was made with various addition agents, in order to decrease the rate of preferential oxidation, and it was found that phosphorus was most beneficial in this respect. After considerable experimentation, the following nominal com-position was accepted as standard: 2.4 per cent nickel; 0.8 silicon; 0.3 phosphorus; balance copper. The physical propertties and certain bearing properties of this alloy are described in the present paper Preparation of Compacts Several methods of incorporating the hardening ingredient (nickel silicide) were studied. Compacts formed from copper, nickel and silicon powders were found to be inferior to those fabricated from prealloyed nickel silicide master alloys, because of the rapid oxidation of pure silicon during sintering. The use of a prealloyed nickel silicide hardener containing 25 per cent silicon and 75 per cent nickel could be further improved by preparing a master alloy, incorporating nickel, silicon, phosphorus and copper, having the following nominal composition~ 25 per cent nickel; 7 silicon; 3 phosphorus 64 copper. This alloy is brittle in the cast condition and can be readily powdered. Sintering Procedure The blended powders were pressed at '5 to 40 tons per sq' in., the pressure depending on the size and shape of the compacts. Sintering was carried out in hydrogen or cracked ammonia atmospheres at

Jan 1, 1946

By Hans Lundberq

IINDUSTRY'S attention is now focused on the production of munitions thereby creating a demand for certain minerals which in prewar days were produced only in limited quantities. Now production of these minerals must he increased from the known deposits and new deposits must be found. Can geophysics help? "War minerals" such as tin, vanadium, tungsten, antimony, manganese, chromium, and cinnabar have no physical characteristics sufficiently different front the country rook to permit their direct location by ordinary geophysical methods. As already demonstrated in work on gold and oil, useful information may be obtained indirectly, however, outlining structural features or geological conditions favorable for the deposition of such ores or the accumulation of oil. Recently, more direct and truly qualitative methods have been brought into a useful and practical stage, and by the combined application of old and new methods a technique has been developed which, it is hoped, will be of importance in the search for these vital minerals.

Jan 1, 1941

By A. Bleier, E. D. Goddard, R. D. Kulkarni

The influence of the collector structure on the amine (RNH2, R=alkyl) flotation of quartz has been systematically investigated using a modified Hallimond microflotation cell. This study focuses on the effect of varying chain length, branching in the alkyl group R, polyfunctionality of the collector molecule, and alkyl substitution on the nitrogen atom. In addition, adsorption at the solution/air interface and electrokinetic results for the solid/solution interface were employed to further elucidate the role ad the interrelation of the structural parameters in the flotation process. Estimates of an electrical double layer attractive energy between the bubble and the solid particle are made.

Jan 1, 1976

By Seymour G. Epstein

Using a modified capillary-reservoir technique, electromigration of dilute solutions of silver in liquid bismuth has been measured with relatively good precision. The effects of experiment duration, temperature. current density, and silver concentration have been investigated. Chemical diffusion coefficients of silver in liquid bismuth were also measured at temperatures ranging from 300°to 600°C. The effective valence of silver in bismuth was calculated as a function of temperature from a comparison of electric mobilities and diffusion coefficients. In an alloy containing 1 wt pct Ag, the electric mobility of silver increased from 1.65 x X sq cm per v-sec at 300°C to 2.38 x 10-4at 600°C; the diffusion coefficient in-creased from 3.0 to 17.5 x 10-5 sq cm per sec over the same temperature range. Calculated values of effective valence decreased from 0.28 at 300°C to 0.10 at 600°c. ALTHOUGH there has been considerable progress in the theoretical treatment of electron-transport properties in liquid metals, the mechanisms of mass-transport phenomena in liquid metals are still not clearly understood. This is especially true for the case of electro migration, alternatively termed elec-trotransport or electrodiffusion, which is mass transport induced by an applied electric field. A thorough knowledge of the mechanisms governing electromigration will considerably aid in understanding the electronic state of an impurity atom in a liquid metal. Electromigration has been long observed and studied in liquid metals and alloys. However, no satisfactory theory to explain the observed effects has been developed. The disparity in the present theoretical treatments, summarized by Verhoeven,1 has been attributed to the difficulty in describing the momentum transfer between electrons and ions and to the lack of precise measurements in liquid metals, especially at elevated temperatures. Prior to the last decade most of the electromigration studies were qualitative, in that only the direction of migration of alloy constituents was determined with any degree of reliability. These results have been summarized by schwarz,2 who was able to measure the electric mobility of several elements in mercury. More recently electromigration in liquid metals has been measured by a variety of techniques, with a varying degree of success. Mangelsdorf3,4 made precise measurements on dilute amalgams at room temperature, using a technique relating changes in composition to changes in alloy resistivity, but was unable to make measurements at elevated temperatures. Using a modification of this technique, Verhoeven and Hucke5 measured electromigration and resistivities in liquid Bi-Sn alloys. However, the resistivity technique is not sensitive to small composition changes and is impractical for very dilute alloys. Verhoeven and Hucke6 also measured electromigration of several solutes in liquid bismuth by adapting the capillary-reservoir method for determining diffusion coefficients in liquids. The reported precision of these measurements was poor, however, primarily due to the large uncertainties in the chemical analyses to determine concentration changes. Belashchenko7 has summarized the recent Russian investigations of electromigration, many of which, however, are of questionable accuracy. The present study was initiated to develop an experimental technique which would be both versatile and sufficiently sensitive to yield precise measurements of electromigration of solutes in dilute metal alloys at elevated temperatures. Using this technique, a comprehensive study of silver in liquid bismuth was made to determine the effects of experimental variables on the apparent electric mobilities. Chemical diffusion coefficients of silver in liquid bismuth were also measured over the same temperature range for comparison with the electromigration data. EXPERIMENTAL TECHNIQUE Electromigration Measurements. Electromigration of silver in liquid bismuth was measured by the capillary-reservoir technique, similar to that used by Verhoeven and Hucke,6 but modified to yield more

Jan 1, 1967

By W. M. Pierce

CORRUGATED sheet zinc has been used abroad for a great many years as a roofing material. In this country it has been in use for about 10 years. From the outset it was recognized that zinc sheets required closer spacing of the supporting purlins than steel sheets. Exact data regarding safe maximum fiber stresses were not available, however, and on occasions the span used was excessive and the sheets sagged. This paper describes both service and laboratory tests to determine safe maximum fiber-stress values for various grades of zinc for use in calculating the proper purlin spacings for any gage and profile under given loading conditions. These tests consist of laboratory loading tests on full-size roof sections over extended periods of time; of actual roof installations erected in conformity with the indications of the laboratory tests and observed over a period of years; of careful determinations of the apparent elastic limit of several grades of zinc, and finally of static tests1 (so-called creep tests) to determine the rate of flow of zinc under a variety of static tensile stresses at definite temperatures. Certain of the individual tests extended over a period of more than two years.

Jan 1, 1929

By H. Foster Bain

FROM time to time geologists and mining engineers, impressed by the heavy demands made on our mineral reserves' by modern industry, and particularly by the steadily mounting rate of production necessary to meet that demand, have issued warnings as to the danger of exhaustion. There can be no dispute as to the fact that mineral deposits are exhaustible. New mineral, is not created to replace that taken from the earth and when a crop of mineral is once harvested another cannot be grown in the same area. The evidence of exhaustion 'of particular oreshoots, deposits, or even of whole districts is familiar to all who have mined. If one were to judge solely from the abandoned mills and prospect holes he would rightly conclude that mining is but a short-lived industry. If one were, furthermore, to assemble the data as to known reserves of almost any of the commonly used minerals, and divide them by the annual tonnage mined, he would come to the same conclusion. If, again, one were to consider the most carefully made estimates of competent men seeking to measure the earth's reserves of minerals and plot against them a projection of the curve of past consumption, he would be justified in viewing the situation with alarm.

Jan 1, 1930

By John T. Norton

In recent years, the damping capacity of metals has come to be recognized as an important index of certain types of structural change. In a number of instances, this property has proved to be particularly sensitive, but insufficient work has been done to permit a general interpretation. There is considerable question at the present time as to just what factors are responsible for the internal dissipation of energy when a metal is carried through a cycle of stress, and these factors must be ascertained if the value of the damping method as a metallurgical tool is to be determined. Since internal stresses are among the chief causes of dissipation of internal energy, or damping capacity, it was thought that a study of the changes in damping during the recovery and recrystalliza-tion of a cold-worked metal might throw some light upon the subject, particularly if the damping changes were correlated with other properties that are better understood. Probably more work has been done on the recrystallization phenomena of alpha brass than on any other metal, so this was chosen as the material for the present investigation. Damping measurements on brass have been made by Förster and Köster.1 They showed that the annealing of a brass that had been cold-drawn to 50 per cent reduction produced a rapid fall in the damping, a flat minimum occurring at approximately the temperature of recrystallization. The damping remained at a low value until grain growth was well under way and then it increased rapidly with increasing grain size. Köster and Rosenthal2 continued the work in greater detail. They pointed out that the damping decrease does not correspond to the hardness drop but occurs at a lower temperature, suggesting that the relief or redistribution of internal stresses has a large effect while the actual recrystallization effect is small. They also show the increase in damping at the higher annealing temperatures. Their curves are reproduced in Fig. 1.

Jan 1, 1940

By John T. Norton

In recent years, the damping capacity of metals has come to be recognized as an important index of certain types of structural change. In a number of instances, this property has proved to be particularly sensitive, but insufficient work has been done to permit a general interpretation. There is considerable question at the present time as to just what factors are responsible for the internal dissipation of energy when a metal is carried through a cycle of stress, and these factors must be ascertained if the value of the damping method as a metallurgical tool is to be determined. Since internal stresses are among the chief causes of dissipation of internal energy, or damping capacity, it was thought that a study of the changes in damping during the recovery and recrystalliza-tion of a cold-worked metal might throw some light upon the subject, particularly if the damping changes were correlated with other properties that are better understood. Probably more work has been done on the recrystallization phenomena of alpha brass than on any other metal, so this was chosen as the material for the present investigation. Damping measurements on brass have been made by Förster and Köster.1 They showed that the annealing of a brass that had been cold-drawn to 50 per cent reduction produced a rapid fall in the damping, a flat minimum occurring at approximately the temperature of recrystallization. The damping remained at a low value until grain growth was well under way and then it increased rapidly with increasing grain size. Köster and Rosenthal2 continued the work in greater detail. They pointed out that the damping decrease does not correspond to the hardness drop but occurs at a lower temperature, suggesting that the relief or redistribution of internal stresses has a large effect while the actual recrystallization effect is small. They also show the increase in damping at the higher annealing temperatures. Their curves are reproduced in Fig. 1.

Jan 1, 1940

Exploration by AS&R of the Nuestra Senora lead-zinc-silver property, located in Cosala District, Sinaloa, Mexico, has proved sufficient ore to warrant placing the mine on an operating basis. Installation of mine plant, concentrator, and townsite, is expected to commence late in 1951. Opening of a lead-zinc property in Nigeria is also being contemplated by AS&R. Private enterprise is being urged by Secretary of Interior Chapman to start a synthetic fuels industry, it is reported. Based on tests at the Louisiana, Mo., plant which produces quality gasoline at costs up to 144 per gal, he predicts that a commercial plant would pay for itself in 10 years.

Jan 4, 1951

By G. F. Loughlin

THE matter of grading Indiana oolitic limestone has been under a cooperative study by the Supervising Architect's office, the U. S. Geological Survey, the Bureau of Standards, and the former Indiana Limestone Quarrymen's Association. As the criteria for grading are necessarily based on a number of geologic and related factors of which those quarrying and using the stone had only imperfect appreciation, the first part of the report is a very elementary account of the origin, structure, and the chemical and physical properties of tie stone, and their relations to durability and utilization, and serves as a foundation for the second part, which discusses grading and pro- poses limits for grades established by the quamymen. Salient features of Part I of a report that has been prepared are the variations in uniformity of stone due to cross bedding, and local uncomformities; the relative prominence of weathering effects on the coarser uneven grained surfaces, and its apparent absence on fine, uniform grained surfaces, although the amount of weathering is the same on each; the attributing "crow feet" (stylolites) to solution under pressure, and the explanation that, whereas the thinnest "crow feet" have no noteworthy effect on weathering quality or strength, the thicker ones are likely to weather out rapidly and to promote splitting; the influence of fracturing on the oxidation of the original gray or "blue" to buff color above the ground water level; the interpretation of chemical analyses and the pointing out that both the gray and buff colors are due mainly to organic

Jan 1, 1929