Search Documents

By A. M. Gsudin, F. W. Bloecher, C. S. Chan-s, P. L. De Bruyn

M ANY elements can now be obtained in radioactive form. The radioisotopes have the same chemical properties as the corresponding inactive forms, differing from them only by their nuclear instability. This combination of properties permits radioelements to act as atomic tracers, the tracer atoms revealing themselves at the time of their decay with emission of electrons and positrons (beta radiation), helium nuclei (alpha radiation), or electromagnetic radiation (gamma radiation). The tracer technique is particularly attractive for the study of surface chemistry problems in general and flotation problems in particular because of its extreme sensitivity. A large proportion of the ionizing events, initiated by the characteristic decay emissions in a radioactive sample, can be recorded by radiation probes of suitable design and geometry. An idea of this sensitivity can be gathered from the following example: assume that 0.001 mg of pure RaD (radiolead), a beta-ray emitter, is used in a flota¬tion tracer experiment. This is 1210 X 10-1 mole; since the fraction trans¬formed per second (the so-called decay constant), is 9.92 X 10-10, the number of ionizing events per second would be (6.023 X 1023 X y,,, X 10-1) X 9.92 X 10-10 = 2.845 X 106. (The decay constant is expressed in sec-'. Its product with the half life, expressed in seconds, is the pure number, natural logarithm of 2 = 0.693. The half life is the length of time required for decay of one half of the total number of radioactive atoms of one particular type.) (See reference (1) at the end of this article.)

Jan 1, 1948

Jan 1, 1879

By K. D. Jacob

MONTANA Phosphate Produucts Co., a subsidiary of The Consolidated Mining and Smelting Co. of Canada Ltd., operates three properties near Garrison, Mont., known as the Anderson, Graveley, and Luke mines. All three are underground operations, mining the same narrow bed at points several miles apart. The Anderson, the oldest and largest of the three, has produced about 700,000 long tons since 1929. The Graveley has produced slightly over 100,000 long tons since 1940, and the Luke, acquired in 1943, is still in an early stage of development. The great bulk of the output has been shipped to the Trail, B. C., plant of Consolidated Mining and Smelting Co. for use in the manufacture of fertilizers. The phosphate seam is the basal member of the Permian Phosphoria formation. In all three mines it has a uniform thickness of 3 to 4 ft. of oulitic phosphate, with a few shaly partings. The overlying part of the formation comprises about 50 ft. of chert and the immediate footwall consists of a few feet of shale and sandstone. underlain by the Quadrant quartzite.

Jan 1, 1944

By AIME AIME

THE program of government drilling, conducted jointly by the U. S. Geological Survey and the Bureau of Mines, has demonstrated the presence in Texas and New Mexico of potash-bearing beds of considerable importance. Information regarding the ex- tent and location of the potash deposits as presented at the non-metallic sessions was of great interest to many engineers. These subjects will be covered in greater detail in later paragraphs. The first session, with about 50 in attendance, convened at 10 a.m. on Feb. 18, with Oliver Bowles, chair- man of the Committee on Non-Metallic Minerals, pre- siding. The first paper was on "Soapstone Mining In Virginia," presented by C. W. Ryan of Lynchburg, Va. The nature and extent of the soapstone deposits of Nelson County were described in some detail. In origin, the soapstone is undoubtedly related to a basic peridotite rock though its mode of formation is some- what uncertain. This main soapstone deposit occurs in three veins, the western, middle, and eastern, the middle vein being of greatest economic importance. Methods of stripping, quarrying and milling the rock were described and the uses of soapstone were enum- erated. In discussing this paper, C. P. Berkey, of Co- lumbia University strongly favored the theory of igneous origin of the soapstone and the need for further detailed geological study. J. L. Gillson of Cambridge, Mass., stated that the Vermont and New York talc deposits were always associated with characteristic minerals, such as, a chlorite of one particular variety, siderite, amphibole, magnetite, and biotite. C. H. Behre of Cincinnati, Ohio, raised the question of parallelism in the soapstone structure and Mr. Ryan stated that such parallelism was in evidence in some parts of the deposits. H. A. Wheeler of St. Louis, Mo., also took 'part in the discussion.

Jan 1, 1929

By William Braden

In view of the current discussion of a proposed change in the United States mining law, abolishing the feature known as the extralateral right of a lode-location, it is an interesting circumstance that in the neighboring Province of British Columbia this feature was tried for eight years and then abandoned. The results of that abandonment have been such as to disprove the proposition, so confidently advanced by many

Jan 1, 1899

By C. J. Sparks, J. C. Ogle, E. A. Starke

DEFORMATION of cold-rolled fcc metals and alloys produces one or the other of two types of rolling textures, usually referred to as the copper type or the brass type. The pure fcc metals, with the exception of silver, develop the copper-type texture when rolled at room temperature. Silver, brass, and many other alloys develop the brass-type texture. Transition from one texture type to another can also occur. Solute additions to pure copper cause a transition from the copper-type to the brass-type texture.' Varying the deformation temperature also produces texture transitions. Copper rolled at -196°C developed the brass-type texture2 and silver rolled at elevated temperatures, 200°C, developed the copper-type texture.374 The work of Haessner,' Smallman and Green,6 and Hu and coworkers3'4 seems to have established an apparent correlation between the type of rolling texture (and the texture transition) and the stacking-fault probability. Thus materials with low stacking-fault energies are thought to develop the brass-type texture while high stacking-fault energy materials develop the copper-type texture. Mikkola and cohen7 measured by X-ray diffraction techniques the stacking-fault probability, a, in the ordered and disordered fcc alloy Cu3Au. Unexpectedly, ordered specimens showed about twice the stacking-fault probability as the disordered ones. Marcinkowski and Zwe118 also found stacking faults in ordered Cu,Au, but not in the disordered CusAu. More recently, Camanzi and coworkers9 have shown that the intrinsic stacking-fault energy of Cu3Au undergoes a considerable decrease (approximately 100 ergs per sq cm) when passing from the disordered to the ordered phase. In general, deformation reduces order'' but some of our measurements showed that some long-range order still remains in Cu3Au after cold reduction by rolling 80 pct. From the above considerations Cu3Au offers the possibility of studying the texture transition in fcc alloys without varying either the temperature or the composition. If the stacking-fault energy correlation is correct, an initially ordered alloy should develop the brass-type texture during rolling while a disordered alloy should develop the copper-type texture. The present communication describes some initial results of experiments designed to investigate this possibility. The rolling textures of ordered and disordered Cu3Au samples were determined after various amounts of deformation. The ordered sample had an initial long-range-order parameter of S = 1, determined from X-ray diffraction. The grain size of both the ordered and disordered samples was the same, and the initial textures of both were also identical and approximately random. No obvious differences in the deformation textures of the ordered and disordered materials were detected up to 35 pct reduction and the (111) pole figures of Fig. 1 resemble that of pure copper. However, with reduction larger than 35 pct and less than 50 pct, a marked deviation from the copper texture was noted in the ordered material. The newly developed orientation was close to the (110)[i12] ideal orientations re-

Jan 1, 1970

By Joseph B. Darby, Paul A. Beck

IN isothermal sections of several ternary systems, the a-phase was found1 to extend in the form of a relatively narrow elongated field, connecting the U-phases that are present in the adjoining binary systems. This was interpreted in accordance with the conception that the U-phase is an electron compound and the ternary U-phase fields were shown in several systems' to extend approximately in the direction of constant average d-shell electron vacancy number per atom. ' However, in the various isothermal sections of the Fe-Cr-Mo system" the ternary a-phase field was

Jan 1, 1958

By R. L., Fullman

During the past year there have been a number of significant investigations that have furnished evidence on the driving forces governing grain growth and on the role played by boundary impurities. Thus Burke has shown that in high purity alpha brass the rate of grain growth in the earliest stages is approximately inversely proportional to the existing grain size. This relation agrees with one derived by Zener assuming that surface energy was the driving force in grain growth. Also in confirmation of the surface energy hypothesis, Burke found that growth virtually stopped when the grain boundaries or even only the grain corners were melted.

Jan 1, 1949

By AIME AIME

COMMITTEES. LOCAL COMMITTEE.-R. C. Crawford, Chairman; Harrison W. Craver, Secretary; Julian Kennedy, Taylor Allderdice, E. W. Pargny, Charles L. Miller, W. H. Rea, S. A. Taylor, M. E. Wadsworth, W. A1. Henderon, A. C. Dinkey, W. L, Jones, E. L. Messier, George Mesta, J. H. Jones, G. H. Riley, S. L. Goodale, D. W. McNaugher. LADIES' COMMITTEE.-Mrs. Taylor Allderdice, Chairman; Mrs. Julian Kennedy, Mr. R. C. Crawford, Mrs. E. M. Herr, Airs. J. W. Marsh, Mrs. T. A. Mellon, Mrs. G. P. Bassett, Jr., Airs. D. M. Clemson, Mr. Charles L. Miller, Mrs. V. L. P. Shriver, Mrs. W. A. Bostwick, Mrs. A. C.. Dinkey, Mrs. A. P. Childs, Jr., Mrs. F. R. Dravo, Mrs. Hermon Griffin, Mrs. W. H. Nimmick, Mrs. F. H. Lloyd, Mrs. S. G. Cooper, Mrs. S. H. Church, Mrs. E. N. Ohl. The Institute Headquarters was established at the Hotel Schenley, where a bureau of information was maintained for the benefit of the visiting members and guests of the party during the time of the meeting. TECHNICAL SESSIONS. The first session, held Tuesday evening, Mar. 1, 1910, in the large lecture hall of the Carnegie Institute, was called to order by Harrison W. Craver, Secretary of the Local Committee. Mr. Craver introduced Dr. John A. Brashear, who extended to the members and guests a hearty welcome to the city of Pittsburg, to which David W. Brunton, President of the Institute, responded. The following papers were presented in oral abstract by the authors: Biographical Notice of Dr. Charles B. Dudley, by Dr. R. W. Raymond, New York, N. Y. Biographical Notice of William Metcalf, by Col. II. P. Bope, Pittsburg, Pa. Development of Hindered Settling Apparatus, by Robert H. Richards, Boston, Mass. (Illustrated by lantern-slides.) A Few Mining Districts in the Argentine Republic, South America, by Z. S. Beyl. (Illustrated by lantern. slides.)

Apr 1, 1910

By L. E. Mannion

Sodium carbonate or soda ash is one of the two principal alkalis of commerce, the other being sodium hydroxide. The use of sodium carbonate is recorded in ancient Egypt, where naturally occurring brines or solid salts were the source of impure soda for glass manufacture. In early modern times until the 19th century, soda ash, as well as potash, was recovered mainly by leaching the ashes of plants. In Europe, during the 18th century, a brown lye for laundering was produced by pouring hot water over burned seaweed. One of the better grades of this kind of material was a product from Spain termed "barilla," which analyzed 24 to 30% Na2CO3 (Hou, 1942). The birth of the modern chemical industry may be said to start with the LeBlanc process for making sodium carbonate from salt, sulfuric acid, and lime. Although invented in France in 1691, England made the most extensive use of it. In 1863 Ernst Solvay devised the ammonia-soda or Solvay process, and by 1874 the first of many Solvay plants was built. These were to supplant the LeBlanc method and dominate soda-ash production until the present time. Although of lesser importance, natural sodium carbonate deposits continued to support operations in various parts of the world. Shortages during World War II stimulated production of "natural" soda ash, particularly at Searles Lake, Calif., and at Lake Magadi, Kenya. Within the last ten years in the United States, a notable surge in production has occurred based on the vast trona deposits in Wyoming. Table 1 lists some principal producers of natural soda ash and the character of the source deposits. Uses and Specifications Sodium carbonate (Na2CO3) is a white, crystalline hygroscopic powder, an aqueous solution of which is strongly alkaline. Most commercial soda ash is a product that must meet high standards of purity and uniformity. Two forms are commonly sold: a fine, powdery material called light ash, and a more coarsely crystalline dense ash; these weigh 32 to 39 and 60 to 66 lb per cu ft, respectively. Dense ash may be produced by adding a little calcium chloride to the sodium carbonate solution to control crystal size and prevent agglomeration. Specifications and typical analyses of light and dense ash in the United States are shown in [Table 2]. Sizing generally achieves about 75% of light ash and 90% of dense ash between +30 and -100 U.S. screen mesh. World use of sodium carbonate now exceeds 24 million tpy, of which the United States produces more than 7 million tons. The market for soda ash is dominated by the glass industry, which uses almost half the supply. Inorganic chemicals, including phosphates and silicates, consume about 30%. Other principal uses include the manufacture of soaps and detergents, petroleum, caustic soda, organic chemicals, and paper; and nonferrous and ferrous metallurgy. [Fig. 1] shows the percent consumption by use of soda ash in Europe, Japan, and the United States. The price of soda ash in the United States remained relatively stable during the 1960s at about $33 per ton; in 1972 it reached $35 per ton. The price in 1975 was $42 per ton. Geology Mineralogy [Table 3] is a list of the more common sodium carbonate-bearing minerals. Anhydrous sodium carbonate is almost never found in nature; only natron, thermonatrite, and trona have been used directly as sources of sodium carbonate. At Searles Lake, burkeite and hanksite are important in the reconstitution of

Jan 1, 1975

By J. W. Downey, J. B. Darby, L. J. Norton

THE only previous investigation of the phase equilibria in the Ta-Pd system was reported by Greenfield and Beck.1 Their work (actually a portion of a much broader survey) was limited to the composition range 50 to 75 at. pct Ta and to a single temperature, 1000°C. The results indicated that no intermediate phases were present at this temperature. They pointed out that this was an unexpected result in view of the fact that niobium, which belongs to the same group in the periodic table as tantalum and has essentially the same atomic size, forms a o phase with palladium.' Also, tantalum in combination with rhodium,' iridium,' or platinum' stabilizes the s phase. By analogy, the Ta-Pd system would also be expected to contain a s phase. The present investigation was therefore undertaken to explore more fully the phase relationships in this system. Alloys were prepared by arc melting on a water-cooled copper hearth in an argon-helium atmosphere. The purity of the starting materials was greater than 99.9 pct. The weight losses on melting were less than 1 pct and therefore the alloys were not analyzed chemically. Specimens were wrapped in molybdenum foil, encapsulated in quartz capsules under a vacuum of at least 1 x 10-5 mm of Hg, annealed as indicated in Table I, and water quenched. Optical and X-ray metallography were used for identifying the phases present in the annealed and quenched alloys. The alloys were resistant to attack by several acids; however, a sodium cyanide electroetch and an immersion etch containing 1 part HF, 1 part HNO3, 2 parts H2SO4, and 5 parts H2O by volume were found satisfactory. The X-ray diffraction patterns were taken with a Straumanis-type Debye-Scherrer camera and filtered copper or chromium radiation. A summary of the phases found in this investigation is presented in Table I. No attempt was made to determine the composition limits of the various phases. The present results indicate that this system consists of two terminal solid solutions separated by at least four intermediate phases at the approximate compositions Ta3Pd, -TaPd, TaPd,, and TaPd3. The Ta-rich solid solution, containing less than 10 at. pct Pd at 1150°C, is in equilibrium with a o phase which is stable in the vicinity of 25 at. pct Pd. The latter phase is also in equilibrium with a bct phase at the equiatomic composition. At high temperatures it appears that the Pd-rich solid solution extends to at least 66.6 at. pct Pd and is in equilibrium with the bct phase. When annealed at 900°C, a sample containing 66.6 at. pct Pd transformed to an unidentified phase designated as X. An X-ray diffraction pattern of this phase contained sharp low-angle lines while the high-angle lines were characteristically diffuse. The observed d-spacings and relative intensities for lines in the low-angle region are presented in Table 11. In the vicinity of 70 at. pct Pd an intermediate phase having the TiA13-type structure is formed. It is stable to at least 1100°C, and presumably dissolves congruently into the ter-

Jan 1, 1963

THE members arrived at Ticonderoga, N. Y., at noon, Tuesday, October 15th, and were received by Mr. Cyrus Butler, Chairman of the Local Committee of Arrangements. During the afternoon the works of the American Graphite Company and the Horicon Iron Company were visited under the guidance of Mr. Butler, President of both companies, and of Mr. William Hooper, Superintendent. An excursion was then made, in carriages, to old Fort Ticonderoga, on Lake Champlain, after which the party were driven to the Rogers Rock Hotel, on Lake George. The first session of the Institute was held in the parlor of time hotel on Tuesday evening. Mr. Eckley B. Coxe, President of the Institute, opened the proceedings with the following address: I shall ask your attention, this evening, to a few reflections upon the subject of mining engineering as a profession in the United States, its past, its present, and its future, and its duties and oppor¬tunities with reference to the proper development of our great min¬eral resources. Thirty years ago, there were scarcely any mining engineers in this country, and but few in England, and there were no institutions where young men could be educated for the profession in the Eng¬lish language. France and Germany have been able for about a century to boast of mining schools of a high character, that number among their graduates such men as Humboldt, Weisbach, Rittinger, Combes, and Gruner. Of the few we then had worthy of the name of "mining engi¬neer," some had studied in the continental academies, and others were graduates in the school of practical experience, and had learned their profession in mines and smelting-works. Their work con¬sisted principally in making surveys and maps of mines and mining properties, geological reports, and analyses of ores ; but the mining engineer whom we often meet with now, who has studied chemistry, physics, mineralogy, geology, mechanics, and drawing; who is more or less familiar with machinery and its construction, and with the practical management of mines or smelting-works, and who is an expert in some one branch of his profession, would have been very difficult if not impossible to find in the United States. The induce¬ments held out to ambitious and talented young men to enter the

Jan 1, 1879

INTRODUCTION It has been impossible for the student, the practicing engineer, and the geologist to find all of the essential elements of mineral appraisal and mineral economic analysis in a single text. Indeed, the most recent texts on mine evaluation are over 20 years old. Many of the basic principles of mine sampling and evaluation have not changed over the ensuing years, but with the advent of the digital computer the entire scope of mineral evaluation has been expanded to encompass superior techniques that heretofore were not possible when using manual methods. The old manual methods for ore reserve computations and the techniques for assignment of area of influence to drill-hole samples are now as antiquated as the Model-T Ford. With the computer making possible solutions that had not been practicable in terms of time and effort, it is important for the practicing explorationist and mining engineer to understand many of the new concepts and principles that can be applied with the resolving power of the computer. Many practicing mineral industry professionals have been disappointed by certain computer programs and thus have some reservations about computers being able to solve their very real problems. Often the gap between the practicing engineer and the ivory tower theoretician applying modern computer techniques is too broad to be bridged with scattered, fragmented publications. PURPOSE AND SCOPE OF TEXT It is the intent of this book to update and to unify a great many scattered reference works used in the mineral industry today. The ensuing pages are addressed both to the professional already working in the mineral industry who needs information on computerized methods as well as to the serious student seeking to grasp the fundamentals and modern techniques of mineral appraisal and feasibility. These techniques are based on sound mathematical principles and theory, with the computer as a tool-but a very essential tool-for the solution of the problems involved. The computer can be of value only if it is programmed by those having sufficient expertise to use its inherent problem-solving capability, and the output is interpreted by those who are sufficiently acquainted with its operation to understand the data it produces. In the pages that follow the author intends to outline in considerable detail all the essen-

Jan 1, 1980

By J. Weertman

The paper of Gifkins and Snowden considers the interesting but difficult problem of determining the stress dependence of secondary (steady-state) creep at low stresses. These authors have concluded that at stresses below 250 psi (2 x 107 dynes per sq cm) the secondary creep rate of lead is proportional to the stress (viscous creep) and is not proportional to the stress raised to about a fifth power. The experimental data considered by them were obtained on tests conducted at room temperature and at 50°C. The lowest stress employed was 50 psi (3.5 X 106 dynes per sq cm). The authors pointed out the main difficulty in determining the stress dependence of creep at low stresses. The creep tests must be run for very long lengths of time. However they made no estimates of when an experimental creep rate determination must be rejected because it does not represent a true steady-state or minimum creep rate. In order to be certain that a creep curve is within the steady-state region, the total creep strain should be of the order of 0.1 to 0.2. For a creep test of a year's duration this requirement implies that a secondary creep rate smaller than about 10-3 per hr cannot be measured reliably. The corresponding creep rate for a 10-year test is 10-6 per hr. The creep rates of the tests that were considered by the authors to prove the existence of viscous creep were of the order of or less than 10-6 per hr. One can conclude reasonably that this data does not prove unambiguously that large strain steady-state creep rate of lead is proportional to the stress in the stress range of 50 to 250 psi (3.5 x 106 to 2 X 107 dynes per sq cm). Another technique can be used to obtain the stress dependence at low stress levels. The creep rate is a very sensitive function of temperature. The creep rate can be increased by very large amounts merely by increasing the temperature. We carried out steady-state creep tests on lead single crystals25 at temperatures up to 320°C. We were able to obtain creep rate data down to stresses as low as 35 psi (2.5 x 10' dynes per sq cm). Our smallest creep rate was 8 x 10-5 per hr. Thus we obtained large strain, steady-state creep rates to even lower stresses than were considered by Gifkins and Snowden. No evidence was seen for viscous creep. The creep rate was proportional to the stress raised to about a 4.5 power down to the lowest stresses. Since there is no reason to believe that changing the temperature should change the stress dependence of steady-state creep, we feel that large strain viscous creep does not occur in the stress range quoted by the authors for lead single crystals or large-grain polycrystalline samples of lead. This conclusion does not imply that viscous creep may nat occur in a lower stress range or in the same stress range for fine grain material or at creep strains very much smaller than 0.1. Support by the U.S. Office of Naval Research is acknowledged. Authors' Reply R. C. Gifkins and K. U. Snowden We thank Dr. Weertman for his discussion and although, as we hope to show, we do not agree with his reservations, we do concur in stressing the importance of ensuring that creep rates are reliably obtained. Dr. Weertman appears to be content to accept n = 1 for low stresses with fine-grained material but not for single crystals. We believe our results show that the former result cannot be accepted without also accepting the latter. We will also show that the probable errors in our minimum creep rates are insufficient to alter our conclusions, that the criterion proposed by Dr. Weertman is arbitrarily restrictive and his alternative experimental approach possibly invalid. 1) A principal result of our Fig. 1(a) is that n = 1 for polycrystalline specimens at room temperature and 50°C for stresses below -250 psi. There was evidence that crystal slip and grain boundary sliding contributed approximately equaily to the overall strain in this low-stress regime. This implies that either a) grain boundary sliding controls slip within the grains or b) both grain boundary sliding and crystal slip independently occur according to mechanisms which give n = 1. Alternative a does not seem acceptable, so we were forced to consider b. This led us to reexamine work on bicrystals by Strutt and Gifkins and plot curves Fig. l(b). Previously Strutt et al. (loc. cit.), had merged these points with others using the Zener-Holloman parameter and thus, we now believe, had been led to overlook the behavior where n = 1. Curves C and D in Fig. l(b) did appear to confirm the hypotheses that n = 1 for crystal slip at these low stresses and the sliding curve F was similarly of the expected form. It was comparatively easy to find a quantitative theory to account for n = 1 for sliding and the similarity of curves C and D to curve F (all obtained from the same set of specimens) led us to feel that the single-crystal curves were valid. 2) We believe the secondary creep rates for both the polycrystalline and single-crystal specimens to be in error by factors c2. In Fig. 6 creep curves for polycrystalline specimens of lead(1) and lead(II) are reproduced as curves a and b, respectively, and curve c is for a single crystal at 100 psi. It is clear that, although the attainment of secondary creep rate takes 2 years for a and 150 days for b, thereafter the curve is linear for periods of 7 and -1 year, respectively. The single crystal has a linear portion commencing after 20 and extending to 90 days. Creep extension was measured directly using a traveling microscope reading to 0.01 mm on gage lengths marked on the specimens; the gage lengths

Jan 1, 1968

By Robert E. Green, Edmund G. Henneke

The velocities of the three possible modes of elastic wave propagation have been calculated for single-crystal copper at 1-deg intervals throughout the standard stereographic triangle. The results are presented as isospeed contours. The deviations between the direction of maximum energy flux and specimen axes are presented as arrows drawn on stereographic projections. The orientation factors associated with dislocation motion on the primary slip system only and also on all twelve slip systems have been calculated for all three elastic waves. The orientation factors associated with a longitudinal standing wave resonant specimen have also been calculated. The results of these calculatians are compared with earlier calculations on aluminum crystals and the relevance of these results to ultrasonic attenuation measurements is discussed. GREEN and inton' have recently outlined a procedure for determining the orientation factors for dislocation damping in single crystals. The stress field associated with a given mode of elastic wave propagation is resolved on the slip systems in which it is assumed the dislocations are vibrating due to this stress field. Since, at room temperature, slip has been observed on a limited number of systems in fcc and hcp metal crystals, it is assumed that these systems are the appropriate ones to use for the resolving process. This procedure has been applied to aluminum crystals by Hinton and hreen' and to zinc crystals by Henneke and Green.3 In the present paper the modes of elastic wave propagation have been calculated for copper crystals possessing orientations at 1-deg intervals throughout the standard stereographic triangle. The deviation of the energy flux vectors from the specimen axis have been calculated for each mode. The stress field associated with each mode has been resolved on the (111)(110) slip systems in order to determine the orientation factors for dislocation damping. MODES OF ELASTIC WAVE PROPAGATION For any direction in a linear homogeneous aniso-tropic material three elastic modes can be propagated. In general, each of these modes has both longitudinal and transverse particle displacements associated with it and thus are not "pure" modes. However, there is always one component which is greatest in either a longitudinal or transverse direction and hence the mode may be referred to as quasi-longitudinal or quasi-transverse, accordingly. For certain axes of high symmetry pure modes may be propagated. The phenomenon of refraction of the energy flux vector is also exhibited by elastic wave propagation in ani-

Jan 1, 1969

By D. K. Crampton

Internal stress and season cracking in brass have been studied for many years and the technical literature contains many data on various phases of the subject. A resume of the literature shows certain fairly well established points upon which various authors are mostly agreed: 1. Season cracking is primarily caused by the presence of relatively high internal stresses, or possibly in some cases by external stresses, or both. 2. A specific corrosion is also essential to season cracking. Certain agents, particularly mercurous salts, mercuric salts and ammonia salts, have such a specific corrosive effect. 3. The tendency to season crack under given conditions increases with increasing zinc content, brass containing less than 20 per cent. zinc being relatively immune. 4. In alpha brass the season cracks are intercrystalline; in alpha-beta brass they lie between the two constituents; and in beta brass they are transcrystalline. 5. The ordinary impurities or added elements in special brasses have little or no effect on the tendency to season crack. 6. Internal stresses can be eliminated, or at least reduced to a safe limit by annealing treatments at temperatures that do not produce visible microstructural changes or appreciable softening of the worked brasses. There are, however, some points in connection with the phenomenon of season cracking which have not been thoroughly investigated, or wherein different authors and investigators are not entirely in agreement. The investigations described in this paper were undertaken to determine: 1. The correlation between mercurous nitrate tests and actual season cracking on long-time atmospheric exposure. 2. The quantitative effect of type and degree of drawing operations on the intensity of internal stress and on the tendency to season crack in brass tubes. 3. The possibility of drawing high-brass tubes in such a manner as to prevent the occurrence of harmful stresses rather than to find a remedy for such stresses once having obtained them.

Jan 1, 1930

By Walter W. Bradley

(Three, papers included, in this discussion are classified as Mining Geology and also as one of the following-A, Metal Mining: B, Milling and Concentration: L, Geophysics. These papers are TP 2255, TP 2092 and TP 2038.) CONTENTS [PAGE Review of Fluorescence as Applied to Minerals, with Special Reference to Scheelite. (TP 1967 by J. W. VANDERWILT, Min. Tech., March 1946. Discussion by WALTER W. BRADLEY) I Geologic Interpretation of Magnetic Exploration on the Mesabi Range, Minnesota. (TP 2038 by R. B. H. JONES, Min. Tech., July 1946. Discussion by ROBERT B. SOSMAN) I A Technique for Photographing Difficult Subjects through a Petrographic Microscope. (TP 2092 by DONALD W. SCOTT, Min. Tech., Nov. 1946. Discussion by HORACE WINCHELL) 2 The Search for Concealed Deposits-a Reorientation of Philosophy. (TP 2146 by SAMUEL G. LASKY, Min. Tech., May 1947. Discussion by T. M. BRODERICK)3 Occurrence of Lead-zinc Ore at Iron King Mine, Prescott, Arizona. (TP 21 go by H. F. MILLS, Min. Tech., July 1947. Discussion by HUGH M. ROBERTS)3 Geologic Relations and New Ore Bodies of the Republic District, Washington. (TP 2197 by LAWRENCE B. WRIGHT, Min. Tech., July 1947. Discussion by AUGUSTUS LOCKE and J. A. RICHARDSON) 4 San Manuel Prospect. (TP 2255 by H. J. STEELE and G. R. RUBLY, Min. Tech., Sept. 1947. Discussion by L. KENNETH WILSON, ELDRED D. WILSON and the author) 5] Review of Fluorescence as Applied to Minerals, with Special Reference to Scheelite WALTER W. BRADLEY*-AS I recall, the first portable units for ultra-violet light of practical use with scheelite were developed at the Nevada-Massachusetts Tungsten Mine at Mill City, Nevada, and were used underground. Ultra-violet lamps are also installed there in the mill, above the gravity-concentration tables, for control observations. Geologic Interpretation of Magnetic Exploration on the Mesabi Range, Minnesota ROBERT B. SOSMAN*-When artificial precipitated magnetite is oxidized at a temperature in the vicinity of 100°C, the oxide is converted into a chocolate brown ferric oxide of the formula Fe2O3, free from ferrous iron, yet possessing the same magnetic susceptibility as the original Fe3O4. This form of Fe2O3 is variously called "ferromagnetic ferric oxide," " maghemite," or "gamma ferric oxide," and has been found as a natural mineral. If a body of magnetite in the Biwabik were to oxidize to this form, the oxidized and leached ore body might successfully conceal itself from Mr. Jones' survey by this ferromagnetic pretense. So far, gamma ferric oxide has not been found on the Minnesota iron ranges. I thought I had found some in the Hibbing pit in 1940, in a strongly magnetic specimen of soft ore differing in color from the prevailing hematite

Jan 1, 1947

By Kenneth B. Ray, George R. Gardner

The application of wet cleaning processes for the beneficiation of bituminous coal has created in some localities a problem in the recovery and disposal of fine solids in the washery water. The maximum allowable concentration of these solids in the washery circuit that is consistent with satisfactory operation of the cleaning units remains a controversial point. It has, however, been generally recognized for a number of years that some degree of control should be exerted over the concentration of such material. Early methods of control involved intermittent or continuous discharge of a portion of the plant slurry into near-by streams or settling ponds, and this persisted even after the adoption of settling tanks or cones. The practice is not always economical, for two reasons: first, because of the waste of coal, and, second, because it is sometimes difficult and expensive to obtain an adequate supply of water. The latter condition often is aggravated by chemical treatment of the make-up water that is necessary to prevent excessive corrosion of plant equipment. The modern approach to this problem has been the adoption of continuous thickening devices. However, because such equipment occupies considerable plant space and is somewhat expensive to construct, the practice of loading these thickeners beyond their rated capacity is widespread, therefore often the performance of such units is not altogether satisfactory. In recent years, European washeries have increased the rate of settling of the fine coal from the slurry by the addition of specially prepared starch solutions. These reagents cause flocculation of the solid particles and thereby increase the rate of sedimentation. The first important work on the flocculation and clarification of coal slurry was done by Henry, who developed the Henry process and used it successfully in Belgian preparation plants. Soon after the initiation in Belgium, the process was introduced into England, where subsequent investigation developed similar processes, which were successfully used in

Jan 1, 1940

By George R. Gardner, Kenneth B. Ray

The application of wet cleaning processes for the beneficiation of bituminous coal has created in some localities a problem in the recovery and disposal of fine solids in the washery water. The maximum allowable concentration of these solids in the washery circuit that is consistent with satisfactory operation of the cleaning units remains a controversial point. It has, however, been generally recognized for a number of years that some degree of control should be exerted over the concentration of such material. Early methods of control involved intermittent or continuous discharge of a portion of the plant slurry into near-by streams or settling ponds, and this persisted even after the adoption of settling tanks or cones. The practice is not always economical, for two reasons: first, because of the waste of coal, and, second, because it is sometimes difficult and expensive to obtain an adequate supply of water. The latter condition often is aggravated by chemical treatment of the make-up water that is necessary to prevent excessive corrosion of plant equipment. The modern approach to this problem has been the adoption of continuous thickening devices. However, because such equipment occupies considerable plant space and is somewhat expensive to construct, the practice of loading these thickeners beyond their rated capacity is widespread, therefore often the performance of such units is not altogether satisfactory. In recent years, European washeries have increased the rate of settling of the fine coal from the slurry by the addition of specially prepared starch solutions. These reagents cause flocculation of the solid particles and thereby increase the rate of sedimentation. The first important work on the flocculation and clarification of coal slurry was done by Henry, who developed the Henry process and used it successfully in Belgian preparation plants. Soon after the initiation in Belgium, the process was introduced into England, where subsequent investigation developed similar processes, which were successfully used in

Jan 1, 1940

GENTLEMEN Herewith are transmitted reports from the Treasurer and of the principal standing committees of the Institute. To these special reports members are referred for details as to the year's work. Despite the unfavorable business conditions obtaining throughout the year, the Institute was able to carry on its various activities without curtailment and without drawing on the surplus accumulated through previous years. In fact, small additions were made to the Life, Member¬ship and various other funds. It is highly desirable that such additions should continue to be made, especially to the Life Membership fund, for reasons reported last year. At present, money must be used from current receipts in order to enable the Institute to fulfill its obligations to those who on joining the organization commuted their dues by a single payment. In addition, with the passage of years the number increases of those who have paid dues forty years or more and who, by reason of age or dis¬ability, are unable longer to practise their profession. These men have supported the Institute through their active professional life and it would be a pity to lose them as members through resignation or for failure to keep up their dues. In accordance with the By-laws the Board has authority to advance such members, on application, to the Honor Roll of Senior Members and to relieve them from further payment of dues. It has been the policy of the Board to do this liberally, but to keep up this, as well as to meet other obligations, it is necessary for money to be provided. It has been estimated by the Treasurer that nearly $50,000 additional should be placed in the Life Membership fund as soon as possi¬ble to meet these obligations without using current income and to that end it is necessary, not only to avoid running behind currently but to earn, if possible, some surplus each year. The small amount transferred to the Life Membership fund from surplus this year was, as a matter of fact, made possible by certain members paying personally bills that were properly chargeable to the Treasury. Such generosity is common among those active in Institute work and probably no year would have closed with a surplus except for it.

Jan 1, 1923