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By I. Iwasaki, K. A. Smith

A chlorination process for treating metal sulfide flotation concentrates is described. The process involves low temperature chlorination combined with sulfur chloride conversion and selective oxidation to produce nonferrous metal chlorides, elemental sulfur, and ferric oxide in a three-stage fluidized bed reactor. The nonferrous metal chlorides may then be water leached, separated, purified, and electrolyzed to recover copper and nickel metals and to regenerate chlorine for recycling.

Jan 1, 1986

By D. A. Schemnitz, O. W. Ellis

Certain alloys1 that, as a result of quenching, are retained in the form of homoaeneous solid solution are known to increase in hardness and strength on standing at room temperature or on heating at slightly elevated temperatures. Other alloys2 that, on rapid cooling, are held in the form of homogeneous solid solution, as, for example, certain steels, behave in like manner on heating to somewhat higher temperatures. The observed increase in the hardness and strength of these alloys, referred to as " aging"' or as "secondary hardness," is widely accepted as being occasioned, either in whole or in part, by the precipitation in submicroscopic form of such constituents as were held in supersaturated solid solution as a result of cooling in excess of a certain critical rate. In earlier discussions of the cause of age hardening or secondary hardness, the question of the hardness of the precipitated particles does not appear to have been raised. At present, however, the general opinion appears to be that age hardening and secondary hardness are occasioned by the precipitation of hard particles within the supersaturated solid substance.3 The authors may be wrong in their belief that the last is a prevailing opinion. Nevertheless, it is thought that the following experiments,

Jan 1, 1925

By J. Lindbo, B. Vigeholm

IN transmission electron microscopy, specimen thicknesses quoted are frequently based upon either traditionally familiar values or a few evaluations representing the whole material. Taking aluminum in 100 kv TEM as an example, average and maximum values are widely accepted as being 2000 to 2500 and 6000 to 7OOOÅ, respectively. It is the purpose of this note to revise these figures and to point out the importance of evaluating individual specimens carefully. All evaluations have been based upon slip trace widths and lattice orientations as determined from diffraction patterns. In many cases where two or more slip systems have been operating the geometrical method described by Crocker and Bevis1 has been applied as a check. The foils were usually oriented to within 2 deg from the exact Bragg angle. Kikuchi patterns were used as indications of correct orientations but not applied in the evaluations. The tilt of the foil surface relative to the beam normal may with certain geometrical relations between the tilt axis and the operating slip plane lead to substantial errors.2'3 Where these geometries were inevitable the samples were omitted in the investigations. Various measures were taken in order to overcome ambiguities, e.g., comparison with neighboring grains, tilts, evaluations based upon two or three slip systems,' and comparison with extinction contour evaluations where s = 0 conditions were obtained. Errors caused by misinterpretation of the slip traces on a micrograph are easily avoided by considering the bright-dark sequence on opposite surfaces and by taking into account the tapering of the foil usually leading to a distinguishable divergence of the pair of traces. In the investigations described here the interpretation was further facilitated as the slip trace formation was observed on the microscope screen and sketches taken down. In a few observations slipping was so violent that the distinction of pairs was considered dubious and consequently given up. To assess average values, thickness evaluations carried out in two independent investigations were analyzed: I) 99.998 pct A1 extruded, cold-drawn, and recrys-tallized to grain sizes between 35 and 500 um were deformed in tension at room temperature. In order to determine the dislocation densities as a function of strain,4 specimens prepared by spark machining and electropolishing in a PTFE holder were analyzed in the electron microscope at 100 kv. Thicknesses were evaluated for 569 selected areas. Histogram I in Fig. 1 shows the results, the average thickness being 4900Å. II) Electropolished specimens prepared from 99.9999 pct A1 with magnesium contents from 0.005 to 0.5 pct rolled to foil and annealed were subjected to fission fragment irradiationa2 For volumetric dose and defect concentration determinations thickness evaluations were performed on 123 areas. Histogram II in Fig. 1 shows the thicknesses of these areas averaging 4250Å. Whereas in investigation I no selection related to thickness has been made, some thin as well as thick areas have been omitted from I1 for experimental reasons. This and the application of two different microscopes although of the same type may account for the difference in average thickness. Assuming a mean error of 10 pct for a single evaluation, the error of the average should be negligible. In order to investigate the maximum transmissible foil thickness in aluminum, specimens were prepared from single crystals with (111) and (110) orientations parallel to the beam, and from polycrystalline material. Maximum values of thickness that could be measured were given by the stopping of the dislocations. The visibility often extended far beyond the end of the slip trace, but with no means of knowing the

Jan 1, 1970

By A. H. Geisler, R. F. Mehl, C. S. Barrett

The complicated nature of the property changes that accompany age-hardening has made it necessary to reconsider and to elaborate the simple dispersion theory.l It has been apparent for some time that more direct information is needed concerning the atomic mechanism of precipitation from solid solution if the theory of age-hardening is to be developed past a purely qualitative stage.‡ Fortunately, in recent years information has been developed which allows us to trace in detail the lattice changes accompanying the process of precipitation from solid solution. This information relates chiefly to the sequence of the several stages of lattice alteration by which the matrix lattice is transformed to the equilibrium precipitate lattice, and permits reasonable inferences to he drawn concerning the states of internal strain that accompany these stages. This information is most complete for the solid solution of copper in aluminum. The equilibrium precipitate is the 0 phase, "CuAl2." This forms in plates, parallel to the {100} matrix planes. The atom pattern and atom spacing on the plane in 0 lying parallel to this plane are roughly similar to those opposite it in the matrix.3 The formation of 0, however, is preceded by the formation of a transition lattice 0': which again lies parallel to the matrix {100} plane, but in this case the matching of atom pattern and spacing across the matrix-precipitate interface is nearly periect; thus there is lattice coherency across the interface and the interface is a plane of separation in only a very limited sense.'8 Particles of 0' may be recognized microscopically and form a well-defined Wid-manstatten figure.* The 0' lattice is recognized by the occurrence of diffraction lines on powder photo-grams or of spots on Laue photograms which may be analyzed in the usual ways to determine the lattice type and the lattice spacings. Very recent research 6, 7, 1 has shown, however, that streaks occur on the Laue photogram at an earlier point in time during the aging process. These streaks have been attributed to a preferential clustering of copper atoms into small platelike elements of only a few atoms in thickness and a lew hundred atoms in diameter, probably of the composition of " CuA12," which may be designated as Guinier-Preston zones or aggregates.1 It is difficult if not impossible to determine the lattice type and lattice spacing in these aggregates. It is possible1 that these aggregates are in fact ?' in a high State of dispersion; the inclination to argue this is strong, as we shall see later. Never-

Jan 1, 1941

By R. F. Mehl, C. S. Barrett, A. H. Geisler

The complicated nature of the property changes that accompany age-hardening has made it necessary to reconsider and to elaborate the simple dispersion theory.l It has been apparent for some time that more direct information is needed concerning the atomic mechanism of precipitation from solid solution if the theory of age-hardening is to be developed past a purely qualitative stage.‡ Fortunately, in recent years information has been developed which allows us to trace in detail the lattice changes accompanying the process of precipitation from solid solution. This information relates chiefly to the sequence of the several stages of lattice alteration by which the matrix lattice is transformed to the equilibrium precipitate lattice, and permits reasonable inferences to he drawn concerning the states of internal strain that accompany these stages. This information is most complete for the solid solution of copper in aluminum. The equilibrium precipitate is the 0 phase, "CuAl2." This forms in plates, parallel to the {100} matrix planes. The atom pattern and atom spacing on the plane in 0 lying parallel to this plane are roughly similar to those opposite it in the matrix.3 The formation of 0, however, is preceded by the formation of a transition lattice 0': which again lies parallel to the matrix {100} plane, but in this case the matching of atom pattern and spacing across the matrix-precipitate interface is nearly periect; thus there is lattice coherency across the interface and the interface is a plane of separation in only a very limited sense.'8 Particles of 0' may be recognized microscopically and form a well-defined Wid-manstatten figure.* The 0' lattice is recognized by the occurrence of diffraction lines on powder photo-grams or of spots on Laue photograms which may be analyzed in the usual ways to determine the lattice type and the lattice spacings. Very recent research 6, 7, 1 has shown, however, that streaks occur on the Laue photogram at an earlier point in time during the aging process. These streaks have been attributed to a preferential clustering of copper atoms into small platelike elements of only a few atoms in thickness and a lew hundred atoms in diameter, probably of the composition of " CuA12," which may be designated as Guinier-Preston zones or aggregates.1 It is difficult if not impossible to determine the lattice type and lattice spacing in these aggregates. It is possible1 that these aggregates are in fact ?' in a high State of dispersion; the inclination to argue this is strong, as we shall see later. Never-

Jan 1, 1941

By John B. Cook

Most of today's open pits take the form of conical-shaped excavations in the relatively flat or undulating terrain surrounding them. Ore is usually hauled uphill from the pit bottom by truck, rail, or skip to crushing, beneficiation, railroad loading, and stockpiling facilities near the edge of the pit. There are, however, a few orebodies whose locations in mountainous terrain causes special problems that generate different technical solutions. LAMCO's 10.5 million metric tons per year high-grade iron mine in the Nimba Range in tropical Liberia is probably one of the most extreme of these exceptions (Fig. 1). At Nimba there is a 2,000-ft difference in elevation between the upper- most levels of the orebodies and the start of the railroad below at the foot of the mountain. Haulage to the crusher is usually downhill at grades of up to 12% dictated by the topography of the rugged terrain. Ore is transported from the crusher down the mountainside by a conveyor sys- tem 10,096 ft long, whose average grade is 18%. The belt is braked by asynchronous generators, feeding power into the local network. The original crusher must be relocated at a lower elevation outside the final pit limit to allow that part of the mountain on which it now stands to be excavated. HISTORY The LAMCO Joint Venture is owned 75% by the Liberian-American- Swedish Minerals Co. (LAMCO) and 25% by Bethlehem Steel Corp. LAMCO is comprised of a 50% interest by the Liberian Government and 50% interest by Liberian Iron Ore Ltd (Fig. 2). This joint venture was launched to develop the high-grade iron ore deposits of the Nimba Range.

Jan 1, 1969

By Nathaniel Herz

(San Francisco Meeting, September, 1915) THE use of zinc dust for precipitating the precious metals from cyanide solutions is well established now in many places, and has many advantages over the shavings method of precipitation. Although much work has been clone on methods of testing zinc dust, as yet no absolutely positive test has been devised to determine the value of the material. Certain facts are known, but often it happens that results on a working scale are not as expected from the laboratory tests. The purpose of this paper is to record some observations made while testing. a large variety of zinc-dust samples in the laboratory. W. J. Sharwood1 has described standard analytical methods, which have been followed, with the changes noted. The regular determinations include zinc oxide, by solution in ammonia and ammonium chloride, lead, and precipitating efficiency. In some cases cadmium was determined by a method similar to that described by J. E. Clennell.2 I will discuss the precipitating-efficiency test in detail. The procedure is as follows: "A solution of potassium silver cyanide is prepared by dissolving 10 grams of silver cyanide (AgCN) and 5 grams of `99 0' potassium cyanide in a little water and diluting up to 1000 cc. It is then adjusted by addition of a little more KCN or AgCN until the solution indicates from 0.12% to 0.15% free KCN by titration with standard silver nitrate. The titration is best made by using a 10-cc. or 20-cc. sample, adding 1 cc. of 2 % potassium iodide, and a slight excess of ammonia, as the end point is then sharper. Or 15 grains of pure crystallized KAg(CN)2 may he dissolved in a liter of water and 1.5 grams KCN added. "Weigh out 0.5 grain zinc dust into a 300-cc. beaker. Add a few cubic centimeters of water and stir until, zinc is well mixed, then pour in 250 cc. of the prepared solution, stirring vigorously. See that all lumps are broken up, and continue stirring for fully five minutes. Stir occasionally (at least every 10 minutes) until the end of two hours from the addition of the solution. Then filter upon an 11-cm. filter, wash precipitate thoroughly, sprinkle with test lead, wrap it carefully in the paper, plaice in a scorifier with about 20 grams test lead, burn paper cautiously in muffle, scorify five minutes, cupel at low temperature and weigh silver. Milligrams silver obtained from 0.5 gram zinc X 0.0606 = percentage precipitating efficiency."'

Jan 8, 1915

By H. Shafick Hanna, Carl Rampacek

Wastes generated by the mining, mineral processing and metallurgical industries now total about 1.8 billion tons annually. The wastes include gases, dusts, solutions and a variety of massive solid mineral materials such as tailings and slags all of which now must be disposed of with a minimum of environmental degradation and at an acceptable cost. Some of the metal and mineralconstituents have potential economic value and their recovery can augment our primary mineral and metal resource supply base. The resource potential of wastes generated by the iron and steel, aluminum, clay, phosphate, copper, coal mining and processing, nonmetallic, and selected secondary metals industries is identified. Information on current efforts being made to recover these resources and the technology now employed or under consideration are presented.

Jan 1, 1980

By R. Casting, J. Philibert, and C. Crussard

APPARATUS described in this paper uses the properties of X-radiation, emitted by substances under electron bombardment, as a means of rapid chemical point analysis. The method is based upon the principles of emission X-ray spectrography pioneered by Moseley in 1913. A very finely focused beam of electrons—the electron probe—is projected on the surface of a sample, which has a very large area compared with the beam diameter, at the point where it is desired to know the chemical composition. The minute volume of the sample which is thus irradiated emits a complex X-ray spectrum consisting principally of the characteristic radiations of the elements present in the volume. Measurement of the wavelength and intensity of each component of this spectrum thus affords a simple method of determining the chemical identity and concentration of these elements. The volume of sample which is analyzed at each position of the beam is limited by the diffusion of electrons in the sample. For an accelerating potential of the electron beam of about 30 kv, which is a convenient value for producing the characteristic radiation, this diffusion extends over a diameter of about 1 µ normal to the beam, and about 2 µ in the direction of the beam. Thus a beam of 1 µ in diameter leads to a volume of about 2 µ in diameter being irradiated. The limits of the analyzed region are thus considerably smaller than those obtained by using spark or arc emission spectrometry, which must extend to about 50 µ at right angles to the beam, and those obtained in X-ray fluorescence analysis, where the penetration of the specimen is considerably greater. The apparatus itself consists of three main parts: an electron optical system. an X-ray spectrograph and an optical microscope. The electron opticai system consists of a tungsten cathode emitting the electrow and a pair of magnetic lenses which focus the electron beam on the specimen to be analyzed. The specimen is prepared in the usual way, as in optical micrography. The X-radiation, emitted at the focal spot where the electrons strike the sample, is analyzed with a curved crystal, Geiger-Müller counter, vacuum spectrograph. The light microscope, designed to observe the surface of the sample in the region to be analyzed, is provided with a reflecting objective placed on the axis of the second magnetic lens. Its magnification is X450. The quantitative determination of an element A in the analyzed region is made by measuring the intensity I, of a strong characteristic line of the element, as emitted from the sample, and then the intensity I (A) of this same line as emitted from a

Jan 1, 1958

By Lynn G. Howell, Alex Frosch

In a previous article1 we have described a technique for measuring the relative intensities of gamma rays from the radioactive elements occurring naturally in geological formations along the walls of a borehole. The apparatus consisted of two Geiger-Müller tubes mounted inside a pressure-tight chamber. Each counter tube was coupled separately to an amplifier and a frequency meter at the surface by means of a multiconductor cable upon which the chamber was suspended. The output currents of the two frequency meters were recorded on a photographic paper as the chamber was moved in the hole. These traces showed remarkable correlation with the geologic formations, as evidenced by comparison with commercial electrical logs.2 Owing to the penetrating power of the gamma rays, logs may be taken in both open and cased boreholes. The apparatus has recently been changed somewhat. One of the counter tubes has been removed and a stage of amplification has been added inside the chamber. This arrangement seems to give a more favorable signal-to-noise ratio and satisfactory logs can be now made in cased holes and also in open holes as previously. Briefly described, the chamber moving in the hole is made of 3½-in. drill pipe and is about 10 ft. long. There is an additional extension about 2 ft. long at the top, inside which cable connections are made. The Geiger-Müller tube is mounted inside the bottom end of the chamber. Above this is the vacuum-tube amplifier with its batteries and transformer. In the top part of the chamber, small 45-volt batteries are mounted, which in part supply the high voltage for the counter tube. Additional voltage is supplied from the surface through the multiconductor cable upon which the chamber is suspended. Also, the output of the transformer in the single-stage amplifier is coupled to another single-stage amplifier at the surface through this cable. The surface amplifier is coupled to the Thyratron-controlled frequency meter, the tank circuit of which consists of a one megohm resistor across which is a bank of condensers varying in

Jan 1, 1940

By Alex Frosch, Lynn G. Howell

In a previous article1 we have described a technique for measuring the relative intensities of gamma rays from the radioactive elements occurring naturally in geological formations along the walls of a borehole. The apparatus consisted of two Geiger-Müller tubes mounted inside a pressure-tight chamber. Each counter tube was coupled separately to an amplifier and a frequency meter at the surface by means of a multiconductor cable upon which the chamber was suspended. The output currents of the two frequency meters were recorded on a photographic paper as the chamber was moved in the hole. These traces showed remarkable correlation with the geologic formations, as evidenced by comparison with commercial electrical logs.2 Owing to the penetrating power of the gamma rays, logs may be taken in both open and cased boreholes. The apparatus has recently been changed somewhat. One of the counter tubes has been removed and a stage of amplification has been added inside the chamber. This arrangement seems to give a more favorable signal-to-noise ratio and satisfactory logs can be now made in cased holes and also in open holes as previously. Briefly described, the chamber moving in the hole is made of 3½-in. drill pipe and is about 10 ft. long. There is an additional extension about 2 ft. long at the top, inside which cable connections are made. The Geiger-Müller tube is mounted inside the bottom end of the chamber. Above this is the vacuum-tube amplifier with its batteries and transformer. In the top part of the chamber, small 45-volt batteries are mounted, which in part supply the high voltage for the counter tube. Additional voltage is supplied from the surface through the multiconductor cable upon which the chamber is suspended. Also, the output of the transformer in the single-stage amplifier is coupled to another single-stage amplifier at the surface through this cable. The surface amplifier is coupled to the Thyratron-controlled frequency meter, the tank circuit of which consists of a one megohm resistor across which is a bank of condensers varying in

Jan 1, 1940

By C. H. Mathewson

CONSIDERABLE progress has been made during the last few years in analyzing the action of plastic deformation in metallic crystals. This is due largely to the development of X-ray spectrographic methods for studying changes in the orientation of single crystals, or of conglomerates, as they occur during the process of plastic deformation, but partly to the widespread knowledge of suitable technique for preparing large (single or variously combined) crystals for direct crystallographic observation under stress or in various conditions of strain. These two methods of studying changes in the crystalline structure of metals may of course be used in conjunction with features of mutual support, but unfortunately the advantage of direct crystallographic observation is lost when we proceed to the study of severely cold-worked structures, owing to the occurrence of real or apparent crystalline discontinuities which become more and more complicated as the amount of plastic action increases. Furthermore, the X-ray methods do not appear to be adequate, at least in their present stage of development, to fix definitely the character of structural alteration in the parent crystal lattice by plastic deformation. The principal question at issue concerns the nature of the crystalline particles that remain after plastic deformation. These are generally known in our American metallurgical literature as crystalline fragments,1 and they seem, indeed, to diffract as individuals causing the Hull pattern of a, severely cold-worked metal to resemble the pattern of a fine powder,2 with certain features of preferred orientation among the particles determined by the manner and intensity of cold working.

Jan 1, 1927

By Arvid Anderson

THE weathering of copper-bearing ores with the formation of a water-soluble salt and the recovery of the metal by leaching and evaporation or precipitation, are processes long known, which have at various times been utilized with more or less commercial success. It is commonly assumed that the technical principles involved are quite simple and their application to a particular case easy. If these assumptions were true, we should anticipate a long list of uniformly successful leaching operations, which is not the case, and one would be justified only in calling attention to either unique or peculiar features of any particular enterprise; whereas, in studying the problems of the recovery of copper from the old workings of the Ohio Copper Co. in the light of available descriptions of other leaching projects, we have not found the assistance hoped for to guide us to the best realization of our own opportunities. It appears desirable, therefore, to call attention to these guiding principles, together with a description of the facts of accomplishment. Justification lies in the fact that the leaching and precipitation of copper at the Ohio Copper Co. mine in Bingham Canyon, Utah, is successful. This success is measured by an average monthly production of 600,000 lb. of copper at an average operating cost, to date, of 3.85 cents per pound at the company's workings, or 6.32 cents per pound after paying shipping and smelter charges on the finished copper. A total of 17,076,099 lb. of copper had been shipped to the smelter from the beginning of operations, August, 1922, to April 1, 1925. Probably these results can be bettered with further study and realization of the factors involved and the devising of methods of meeting them. It is now an assured fact that the enterprise will have a relatively long and continuously profitable life and that its reserves will not, nor cannot, be suddenly and permanently depleted.

Jan 9, 1925

By Hassell E. Hunter

The Wyoming Minerals - Conoco Crownpoint Joint Venture represents the first time that big hole drilling has been exclusively used to develop a privately financed mine. Three shafts, one ten feet in diameter and two six feet in diameter, have been successfully drilled to depths of 2243', 2188' and 2188' respectively and lined with hydrostatic designed steel casing. The largest shaft is to be used to as a development shaft to handle muck and water from enlargement and station excavation of the other two shafts. A reverse fluid air assist circulation system with potassium base mud was used during drilling. The mud was cleaned by settling in steel lined tanks with assistance from cyclone type sand separators. Deviation was monitored with wireline gyroscopic surveying instruments at 30 foot intervals. Horizontal departure did not exceed 16 inches off perpendicular. Casing was designed to withstand full hydrostatic pressures with a 1.5 safety factor for the large shaft and 1.25 safety factor for the two smaller shafts. All casing welds were x-rayed prior to lowering the casing into the hole. Cementing the annular space completed the operation. The total time to mobilize, drill and move off the three shafts was 363 days. The drilling operation was completed ahead of schedule and under budget.

Jan 1, 1982

By Charles Catlett

The terms " developed " and " undeveloped " are necessarily relative and cover a wide range; but the latter is here applied to cases in which the information at hand falls short of a clear demonstration of values, and conclusions must be reached frorn a study of the geological conditions of the particular deposit, interpreted in the light of similar and closely-related deposits. Such an inquiry might be characterized as an effort to reach reliable conclusions from insufficient data. But the engineer

Jan 1, 1909

By W. Barbarowicz, H. E. Uhland

AT the Noralyn mine and mill of International Minerals & Chemical Corp. in Bartow, Fla., process instrumentation has been incorporated in three departments-mining, flotation, and preparation. Use of the dragline is the most difficult aspect of the mining operation to control automatically. At the Noralyn mine there are two draglines, a Bucyrus-Erie 1250-B with 29-yd bucket and 235-ft boom and a Bucyrus-Erie 1150-B with 21-yd bucket and 215-ft boom. These are equipped with a minimum number of instruments, but further instrumentation would increase the operator's efficiency.

Jan 7, 1957

BECAUSE gold is a compound mineral praised by philosophers and all wise men as being of the highest perfection among all mixed minerals, and because of its great beauty, it is the universal opinion that it possesses extraordinary powers which are beneficial to man. For this reason it is the thing esteemed most highly in this world, after living creatures. Hence, I, too, in order to honor it, wish to begin by speaking of it now rather than of any of the other metals, and I wish in particular to tell you of its generation and of its most obvious qualities, for, although it is a metal very widely known and one that is desired and sought after by all kinds of persons, I know of few who take the trouble to find out what its substance or natural form may be. But, in order that you too may not be one of those who know it only by name or by the appearance that it shows outwardly to us, I tell you that its original and peculiar materials are none other than elemental sub¬stances, with the quantity and quality of each proportioned equally one to the other and very finely purified. From this union of elements which are of equal force there is born a pleasing and perfect elemental mixture,* and then after fermentation and decoction the elements finally become

Jan 1, 1942

By A. C. Fieldner, F. H. Gibson, W. A. Selvig

A foRmer paper1 described in detail various methods of calculating coal analyses to obtain the composition and calorific value of the pure coal substance—that is, of the coal free from its mineral matter. The paper included a table showing calorific values of pure coal, as calculated from float-and-sink portions, by means of the Parr formula for "unit coal" and by the customary moisture-free and ash-free formula. A modification of the Parr formula was proposed, based on the assumption that one-half the sulfur present in Coal occurs as pyritic sulfur and one-half as organic sulfur. In the published discussion of the paper Cady gave a table of results on a large number of Illinois coals as obtained by the Parr formula and the proposed modification thereof. The results obtained by Cady indicate that the Parr formula applies better to Illinois coals than does the modified formula proposed by Fieldner and Selvig. The present paper gives results obtained by applying the modified Parr formula to the analyses of the float-and-sink portions of the coals shown in the former paper, and results obtained by applying the Parr formula, the modified Parr formula, and the simple moisture-free and ash-free formula to various coals of the United States ranging in sulfur content from less than 1 per cent to more than 4 per cent sulfur. A graphic method of estimating the calorific value of pure coal and determining the relation of the coal ash to the mineral matter of coal, as proposed by Stansfield and Sutherland,2 was applied to a number of coals, and the results are given herein. Testing Formulas with Float-and-sink Separations The former paper by Fieldner and Selvig gave heat values of pure coal of the float-and-sink portions of 21 coals, as calculated by the Parr formula

Jan 1, 1932

By H. C. Chang, N. J. Grant, A. R. Chaudhuri

During the creep of coarse-grained polycrystalline magnesium at elevated temperatures, a nonbasal type of slip was found to play an important role in the deformation processes. The nonbasal slip traces were examined metallographically in eight specimens (13 grains) and the observed glide plane located stereographically for each grain. The tests were run at 500&apos; and 700°F at stresses of 148 to 786 psi. Based on these measurements and theoretical calculations, the crystallographic elements for nonbasal slip were determined. WHEN a metal deforms by slip, the conventional appearance of the slip bands on the surface of a specimen is that of straight lines. Such is the behavior of the face-centered-cubic metals, as for example, aluminum. The particular slip system on which slip occurs in these metals is governed by the criterion of resolved shear stress. Work on the body-centered-cubic metals a-iron,&apos;. &apos; molybdenum, and columbium4 has shown that the process of slip is somewhat more complicated than the simple gliding of one close-packed plane of atoms over another in a close-packed direction and that it results in the formation of wavy and irregular slip traces on the surface. The recent reviews and experiments of Vogel and Brick and Chen and Mad-din3 show that, for the body-centered-cubic metals, the resolved shear stresses along the planes and the degree of close-packing do not necessarily determine the slip system. Theirs and other investigations indicate that a complete understanding of the slip process in the body-centered-cubic metals is not yet possible. However, one behavior displayed by all these metals is that the slip direction is invariably one of the close-packed directions <11l>. The wavy nature of the slip-band traces has been explained on the basis of cooperative slip by planes sharing this same slip direction.1&apos;3l&apos; It is generally acknowledged that, when the hexagonal-close-packed metal magnesium (axial ratio c/a = 1.624) deforms by slip at room temperature, it does so by basal slip in the close-packed direction <1I%>. This type of slip has the conventional appearance of straight lines and is governed by the critical shear-stress law. Schmid and coworkers" showed that basal slip was operative in the temperature range of —185" to 300°C (—300" to 572°F). Work by Servi, Norton, and Grant6 has shown that, during the creep of coarse-grained aluminum at high temperatures, new slip systems come into operation. The existence of a new high temperature slip system at temperatures greater than 225 °C (437°F) for magnesium was suggested also by Schmid. This was later indicated by Bakarian and Mathewson&apos; to be slip along the pyramidal planes (10i1) in the close-packed direction <11%>.* They * Mention will be made in the text of pyramidal planes and prismatic planes. The pyramidal planes referred to are the type I. order 1 of the form {10il); and the prismatic planes of the type 1 of the form (10i0). For the sake of brevity, they are termed in the teat as pyramidal (10il: and prismatic (10i0) planes, respectively. Where reference is made to the pyramidal plane type 1, order 2 of the form {10i2), they are referred to as the pyramidal planes of the type (10i2:. observed that this kind of slip resulted in irregular markings on the specimen surface. According to them, a possible cause for the appearance of the markings was due to "limited accessory slip on the pyramidal {10i2) planes." Burke and Hibbard," on deforming a single crystal of magnesium at room temperature, found evidence of slip on a pyramidal plane {1011). They explained it as being due to the effect of grip restraints. It is pertinent to note at this point that, although basal slip has received a fair amount of attention, only two specimens have been investigated, that of Bakarian and Mathewson and of Burke and Hibbard, to establish the elements of nonbasal slip in magnesium. During the study of the deformation mechanisms

Jan 1, 1956

By C. A. Heiland

THE investigations described were made on a portion of Clear Creek basin near Golden, Colo. (A portion of the area under survey is shown in Fig. 1. The photograph was taken in the vicinity of station No. 2 of Line II.) Three principal purposes were in the minds of the investigators: 1. To repeat with modern, more sensitive and more reliable instruments magnetometric placer investigations previously made. 2. To disprove the recently advanced theory that deposits of the glacial period have no pronounced magnetic effects. 3. To develop in detail the theory of the magnetic effects produced by placer deposits. Six years ago, the first magnetic observations were published, which proved that it is possible to locate gold-bearing channels with relatively crude instruments.1 Two years ago, K. C. Laylander published results obtained with similar instruments.2 The measurements of the latter were discussed by the senior author of this paper.3 At that time, however, the material available for such a discussion was somewhat scarce and not made with the most modern magnetic instruments, although very brilliant results were obtained. Therefore, the senior author felt that magnetic investigations should be made on very clear geologic conditions with the most modern instruments.

Jan 1, 1928