Search Documents

By Thomas N. Walthier

ROSPECTING for uranium in the East is hampered by the lack of bedrock exposure due to extensive overburden and residual soil. But, despite the problems of this physiographic province, it has not been ignored in the search for radioactive materials. Since 1951 both the U.S. Geological Survey and the Atomic Energy Commission have had field parties in the eastern U.S. Tempo of private prospecting is increasing, and many discoveries have resulted. AEC work so far has been concentrated in the areas of most numerous discoveries-Pennsylvania, New Jersey, and New York. Accounts of uranium mineralization in the eastern U.S. are found in the old literature and one site in the Mauch Chunk area of Pennsylvania has been known since 1874. In 1949 McKeown examined the original occurrence there and found another southeast of the town. The deposit appeared to have commercial possibilities and a short period of production began in July 1954

Jun 1, 1955

By L. D. Muller, C. P. Sayles

When minerals are mined in arid or semiarid areas where water is at a premium, dry processing is a natural route to take for concentrating or classifying the values. Until recently though, dry processing technique were limited by the lack of suitable equipment. With the advent of the pneumatic pinched sluice at Warren Spring Laboratory, Stevenage, Hertfordshire, England, a new tool emerged to fill this gap and it has the potential of providing industry with a high output concentrator or preconcentrator for dry natural ores and secondary materials. The pneumatic pinched sluice gives every indication of fulfilling these requirements with the added advantage that with homogeneous materials-such as crushed limestone or quartzose sands-it may alternatively operate as a high throughput dry classifier or sizing device. An industrial version of the equipment is now being manufactured by Dryflow Separators Ltd., as sole licensee for the National Re- search Development Corporation.

Jan 1, 1971

By John B. Hastings

THE origin of the watery vapors of vulcanism has always been an object of interest and speculation to the seismologist, and as theories of the genetic origin of ore-deposits have of late years been pretty well narrowed down to the expiring forces of plutonic action, the same question has had a lively interest for mining engineers and geologists, as is well shown by the discussions of the subject in our Transactions. The important part taken by volcanic emanations in the origin of pegmatites and quartz-veins, described in my paper, Origin of Pegmatite,1 and their latent power to concentrate into useful deposits such scattered gold as occurs in the Hartsel granite, make a discussion of their derivation but a natural third and final step. It is conceded that enormous amounts of vapor accompany volcanism, though perhaps we are apt to forget that steam has 1,700 times the volume of water, besides which the column seen over Vesuvius and other volcanoes is greatly mixed with air; the immensity of such volumes compared with solids and liquids is shown by the experiment of Gautier, who, by heating dessicated granite to 100° C., evolved from it uses 20 times, and steam 90 times, its own volume. Dana appraised the average amount of water left in ordinary rocks as 2.5 per cent. T. M. Read estimated that the Mississippi river carries to the sea annually 150,000,000 tons of rock material. If these Mississippi sediments, as deposited, contained 20 per cent. of water, it would be 600,000,000 cu. ft., or 4,500,000,000 American gallons, annually. Allowing the vapor suspended over a volcanic cone to be mixed with 80 per cent. of air, this amount of water converted into steam would replenish anew, every 9 min., a column 15,000 ft. high, 2,000 ft. in diameter at the base, and 10,000 ft. at the top. Read's estimate is only half of the amount given in a more recent and probably correct one .2

Jan 5, 1908

By R. W. Waterfill

MANY existing ore deposits of valuable metals have been worked out in their upper surface levels and the continued productivity of these mines is dependent on their extension to greater depths in the earth. The maximum depths at present reached are about 6000 to 8000 ft. below the surface, with no evidence of an impoverished ore vein. These mines are widely distributed; some of the best known are in South Africa, Brazil, India and in the western sections of the United States. Among the factors which increase the difficulty of working these mines at increasing depths are hoisting, rock pressure and temperature. The manner and effectiveness with which these problems arc met will, no doubt, determine in a large measure the ultimate depths to which any mine can be profitably worked. The most critical of these three factors at present is the increase in temperature with depth. The high temperature and humidity in many of these mines at present are severely detrimental to the health of the workers and greatly hamper their efficiency. Some have almost reached a condition in which the human system cannot survive. The problems involved in the cooling and ventilation of mines have all been ably analyzed and presented in previous articles. For this reason, only a résumé of conditions affecting the cooling and conditioning of deep and hot mines will be given in this paper before attention is directed to possible methods of improving atmospheric conditions in the working levels. Physiological Effects of Temperature, Humidity and Air Motion Many data on the physiological effects of different atmospheric conditions on the human system have been compiled and published through the combined efforts of the American Society of Heating and Ventilating Engineers, the U. S. Bureau of Mines and U. S. Public Health Service. These data were not primarily developed around the conditions existing in deep mines, but the upper temperature limits of the investigations extend into, and are applicable to, mine atmospheric conditions. While the exact values of the standard comfort conditions, established for persons of such habits as those employed in detecting the different degrees of comfort, might not produce identical effects upon persons inured to

Jan 1, 1929

Cobriza can only be described as the Machu Picchu of the mining business. This relatively new mine of the Cerro de Pasco Corp. in Peru, subsidiary of The Cerro Corp., was put on stream in December 1967. The best way to get there is to go in the company's HelioCourier with pilot Paco Perez. The plane is mostly engine and the pilot is without nerves. The trip starts at an elevation of 12,000 ft at La Oroya and ends at the Cobriza air strip near the top of the Continental Divide at 14,200 ft. Perez says this is the highest air strip in the world. The flight is made at an altibude below many of the peaks and it is easy to pick out the Inca Trail which follows the ridge line of the top of the Andes. Inca ruins are also visible from the aircraft. The drainage pattern, with a surprising number of lakes and rivers, can be seen and so, too, can a great deal of structural geology and numerous agricultural settlements dotting the altiplano. Cobriza is in the monta[n]a on the east side of the Andes, which is characterized by tropical climate and vegetation, an abrupt change from the frosty mountain atmosphere. The mountainsides are precipitous and the bottoms of the steep valleys are channels for roaring rivers. Such is the setting of Cobriza, above the swift cataracts of the Mantaro, benched out precariously at about 8700 ft elevation. The mountains rise in majestic splendor and the sun comes up late and sets at 3: 30 on winter afternoons. One of the lowest of the Cerro de Pasco camps, it is the most remote.

Jan 11, 1969

The income of the Institute is derived from dues, subscriptions to MINING AND METALLURGY and sale of publications. These sources are fortunately supplemented by the interest from invested funds now amounting to over $500,000, a considerable portion constituting endowments for especial purposes. Aside from the medal funds the principal endowments are the James Douglas Fund for support of the Library, the Rocky Mountain Fund and the Seeley W. Mudd Memorial Fund. The income from the two last named is available for the support of research and a variety of other purposes. It is allocated by the Board of Directors upon recommendation of standing committees in each case. An active effort is being made to increase the endowments of the Institute, it being felt that unusual opportunities exist for research and public and professional service through the organization and at a minimum of expense. J. V. W. Reynders is chairman of the Endowment Committee.

Jan 1, 1923

By A. Cochardt, D. H. Feisel

HE success of the sintered aluminum powder material (SAP)' in raising the maximum useful temperature of aluminum alloys has stimulated effort in investigating similar systems in which the metallic matrixes have higher melting points. Examples of such systems which have been studied are nickel-alumina,2, 3copper-silica,4 copper-alumina,4 titanium-cerium oxide,5 and 80/20 nickel-chromium,8 cobalt,= and molybdenum7 matrixes with various hardeners. Conventional precipitation-hardened high-temperature alloys are often thermally unstable in service. The original fine particles that are responsible for good strength properties grow in size at elevated operating temperatures, a process termed "over-aging." This growth of precipitated particles causes a gradual loss in strength properties. A previous paperb describes the factors that govern the process of overaging, and estimates the time required for overaging of a nickel-alloy matrix dispersion-hardened by various precipitates such as are found in current high-temperature alloys, and by alumina. These calculations indicate that nickel-base alloys hardened with Ni3Al, Tic, or TiN are quite unstable at 1340" F (727°F). Such alloys should overage within a few hours at that temperature. A nickel-base alloy hardened with alumina, on the other hand, should behave differently. It should not overage appreciably within a thousand years. It was further shown8 that the thermal stability of the oxide-hardened alloy is mainly due to the low solubility of oxygen in equilibrium with alumina in the nickel-base matrix. Since the oxygen solubility is small, little oxygen can diffuse, and structural changes require very long times. This paper illustrates the effects of time and temperature on the structural stability of nickel alloy matrixes hardened by dispersions of Ni3A1, Ni3Ti, Tic, and alumina, and of nickel-chromium matrixes hardened by alumina. Hardness measurements and metallography have been used as a measure of structural stability. EXPERIMENTAL PROCEDURE Using the best information from published phase diagrams,'-l4 compositions of the Ni-Al, Ni-Ti, and Ni-Ti-C alloys were determined so as to have 5 vol pct of precipitate at 1350° F(732°C), the temperature selected to illustrate the effect of time on structural stability. Table I lists the chemical compositions of these alloys. Standard laboratory melting and alloying techniques were used in preparing ingots of the F-Series of alloys. The cast ingots, 1 3/4 in. in diam, were forged to 3/8-in. diam rods.

Jan 1, 1960

By Robert Mehl

A STUDY of the structures arising from the decomposition of the a solid solutions in the Cu-Zn and the Cu-Al systems is of peculiar interest in the study of the mechanism of precipitation from solid solutions. It is possible in these alloys, by varying the composition within the ß field, to precipitate from the same basic lattice phases having different lattice structures. It has been rather generally assumed heretofore that the type of structure originating from the decomposition of a solid solution-the Widmanstätten structure-is determined by the lattice structure of the parent solid solution alone. In the first paper of this series1 evidence was advanced which threw doubt upon this hypothesis; but definite proof of the correctness or incorrectness of the hypothesis should be forthcoming from a study of these alloys, for if the structures originating, for example, from the precipitation of the a phase from ß and of the -y phase from the ß in the Cu-Zn system should be shown to be crystallographically different, the hypothesis would necessarily be held as definitely disproved. Furthermore, the newer proposal enunciated in the first paper of this series-that the origin of the Widmanstätten structure lies in a cooperation between the lattice of the parent solid solution and that of the precipitate-which at present seems the only alternative hypothesis, would in such an event be given added weight. The work here reported shows that the Widmanstätten structures originating in the precipitation of the a phase from the a and in the precipitation of the -y phase from the ß in the Cu-Zn system are indeed crystallographically different; and incidentally presents some new descriptive information on the Widmanstätten structure from a more general point of view.

Jan 1, 1931

By Robert H. Richards

The group of four papers on ore dreseing read at the Butte meeting, all of them dealing with the recent developments at the Great Falls and Washoe plants of the Anaconda Company, form an extremely important contribution to the subject of ore dressing. It proves the efficacy of the new hindered-settling principles first brought out in a paper entitled Close Sizing Before digging' and later elaborated in a paper entitled Development of Hindered-Settling Apparatus: and it is the first large demonstration on this class of mill that has been made. It must be very gratifying to all mill men to have these papers at hand, charged with careful investigations and results pointing to the conclusions reached; the papers cannot fail to be a great help to every designer of mills and to mill men who are working on this class of concentration. The papers have dealt with their subjects so completely and have demonstrated every point from beginning to end in each case so thoroughly it leaves little for the commentator to say in the way of criticism. Therefore it seems best to him to confine himself to adding a few points of history which he believes will be interesting to the readers. Referring to the paper by Mr. Wiggin, and to the fact that the Richards hindered-settling pulsator classifier was turned down, the writer wishes to say that this classifier was the first of its kind that had ever been introduced, and since that time it has undergone great developments which he believes would overcome the difficulties encountered in the test,. In fact, there was one test made at Great Falls which with the Wilfley tables and vanners brought all the tailings down to 0.36 per cent. copper except the fine slime. Since that time, and since the classifier has been further developed, in one Colorado mill it proved a wonderful amalgam catcher, catching in all

Jan 1, 1914

By H. Conrad, V. V. Damiano, G. J. London

The slip mode activated during the c axis compression of single crystals of commercial-purity ingot SR beryllium, high-purity (twelve-zone-pass) beryllium, and Be-4.4 wt pct Cu and Be-5.2 wt pct Ni alloys in the temperature range of 25° to 364°C was determined using two-surface slip trace analysis, slip-step height analysis, and electron transmission microscopy. All three techniques indicated the occurrence of copious pyramidal {1 122) (1123) slip in the alloys over the entire temperature range, the amount increasing with temperature. Pyramidal slip was also indicated in the high-purity beryllium by slip trace analysis and electron transmission microscopy, but the amount was somewhat less than in the alloys. For the commercial-purity ingot crystals, only a very small number of pyramidal slip lines were observed, and these were in the immediate vicinity of the fracture surface. No pyramidal dislocations could be detected by electron transmission microscopy in this material. Dislocatransmissiontions with Burgers vectors [0001] and +(ll20) were identified by electron transmission microscopy inthe (1122) slip bands, as well as those with the j (1123) vector. This was interpreted to indicate that the edge components of the 3(1123) vector dislocations activated during c axis compression dissociate upon unloading according to the reaction i (1123) — [0001] + 3(1120) THE microstrain c axis compression of single crystals of commercial-purity ingot SR beryllium (99.6 pct), high-purity twelve-zone-pass beryllium (99.98 pct), Be-5.24 pct Ni and Be-4.37 pct Cu alloys was described in a previous paper.1 This paper covers in detail the analysis of slip traces observed on two mutually perpendicular lateral surfaces of these specimens, and a detailed description of transmission electron microscopy studies performed on foils cut from the bulk crystals after they had been deformed to fracture in the c axis compression. Observation of slip traces on single surfaces of deformed single crystals are generally insufficient to positively identify slip or twinning modes. The use of two carefully cut and oriented perpendicular surfaces can greatly aid in the positive identification and index- ing of slip traces, although even this technique may be quite inadequate if more than one type of slip system operates and if an insufficient number of traces are observed on the surfaces. The problem is greatly simplified for symmetric cases like that for c axis compression of an hep crystal such as beryllium, in which the operating slip systems are all equally inclined to the direction of the applied stress, and each slip system of a given slip mode has an equal chance of operating. For such cases, the traces of any given slip mode observed on the surfaces cut parallel to the c axis are symmetrically tilted about the c axis. It is therefore possible to quickly determine whether one or more slip modes are operating. Confirmatory evidence in support of the observations made on the external surfaces can be obtained from foils cut from the deformed crystals and examined by transmission electron microscopy. This latter technique serves to identify not only the operating slip plane but also the Burgers vector of the dislocations which participate in the slip. For this purpose, a simplified technique based upon a double tetrahedron notation is used in the present paper. The planes and directions in the hep lattice are all designated by letters rather than indices and extinction conditions are easily determined if the Burgers vector lies in the plane contributing to the diffraction. RESULTS 1) Slip Trace Analysis. The standard (0001) stereo-graphic projection of beryllium is shown in Fig. 1. The two mutually perpendicular, lateral surfaces of the compression specimen are represented by the diametrical planes AA' and BB', also referred to as surface A and surface B. For the specific case represented (a Be-5.24 pct Ni specimen deformed by c axis compression at room temperature), the A surface is tilted 5 deg to the (10i0') plane and the B surface is tilted 5 deg to the (1120) plane. Two surface trace analyses may be facilitated by examining in turn the intersection of various great circle traces of specific pyramidal planes with two surfaces and comparing the angles made with the (0001) plane with those actually observed on the two surfaces. One then identifies the slip traces by trial and error on a best-fit basis. The (1122) type planes (it was found that slip occurred on these planes) are shown plotted on the stereographic projection in Fig. 1. One obtains directly the angles between the (0001) plane and the {1122) traces by measuring the angle from the periphery to the point of intersection along the lines

Jan 1, 1969

By M. B. Ramachandra Rao

THIS paper records the results of the earth resistivity surveys made in the Godavari river in connection with the Ramapadasagar project. After describing the topographical and geological features of the area, the results of the investigation at the several sites have been mentioned. Further, a detailed account has been given of the resistivity methods adopted, the apparatus used and the interpretation of the curves. The resistivity measurements carried out over the water course have been specially outlined, and a review of the verification of the electrical indications by drilling in a number of cases, has also been presented.

Jan 1, 1947

By H. W. Rogers

THE first steam shovels used in this country were built by the Otis Company, of Boston, about 50 years ago, but as they were of very crude construction and rather unsuccessful only a few were built. For possibly 10 years prior to 1884 successful steam shovels were made and used on certain classes of work, but it was not until that time that they were manufactured in quantities and began to play an important part in all classes of excavation. From that time up to the present day there have been gradual but continuous improvements on the original shovel, not only in the mechanical construction, but also in the design of boilers and engines which are best adapted to this class of service. In proposing a change from steam to electric operation we have to deal with a steam equipment which has not only proved its worth but has probably reached its highest stage of development and efficiency. That the electric shovel is a possibility cannot be denied, as at present from 12 to 18 shovels are in operation in this country. These shovels may be divided into three classes: the friction electric, which is operated by a single constant-speed motor with friction clutches; the three or four motor direct-current equipment, and the three or four motor alternating-current equipment. It is the second and third classes that I wish to deal with, as the first class does not compare favorably with the steam shovel so far as speed is concerned, although it may be operated as cheaply. There is probably no other class of machinery that presents a duty cycle as severe as that of the shovel, which is very short, varying from 7 to 12 sec. on the hoist, from 7 to 12 sec. on the thrust, and from 10 to 18 sec. on the swing, making a complete cycle in from 17 to 30 sec., and the motor to meet these requirements must have a sufficiently low armature inertia to permit of rapid acceleration and quick reversals under small power. It should also be a motor of rugged design, as it must be subjected to severe overloads and shocks and frequent reversals. This is especially true of the hoist motors and, to a lesser degree, of the swing motor; the thrust motor being practically stalled during the digging operation, although it may revolve or overhaul, according to conditions, and is operated at full speed only after the hoisting operation is completed.

Jan 2, 1914

By Henry Faul

Measurement of radioactivity of rocks and ores has developed into a complete method of geophysical exploration. The problem falls into three natural categories: (1) surface radiation measurement in the field and underground; (2) radioactivity logging of drillholes; and (3) laboratory analysis of samples. Portable counters are used in the field for tracing radioactive formations and for quanti tative estimates of radioactive content of surface rock. Wartime advances in battery design make it possible to construct small precision counters that can be carried easily. Even the smallest conventional diamond drillholes can be logged, and actual content of the radioactive element can be measured. The exact grade of very thin active layers or veins can be estimated only approximately. Samples may be analyzed for their alpha, beta or gamma activity, and beta assaying is the best suited to rapid routine operation. Simple calibration with standard samples is sufficient for rough work, but a density correction is necessary when greater precision is required. Samples with high emanating power should be fixed and stored for three weeks to reestablish the radium-radon equilibrium prior to precision assaying. Carno-tite can be fixed by sintering or molding with plastics. Among the important new developments, a low-voltage Geiger tube has been 'designed recently, and crystal scintillation counters hold great promise for high-efficiency gamma-ray measurement. Introduction During the last few years we have witnessed an unprecedented rise in the demand for radioactive minerals, coming as a direct consequence of the discovery of nuclear fission and subsequent developments, the full impact of which is by no means in sight even now. It remains certain, however, that radioactive minerals, and especially those which can be used as ores of uranium and thorium, will continue to be of great interest not only to the prospector and mine operator but also to the various inspection parties envisioned by most of the schemes advanced for the control of nuclear energy on a world-wide basis. It is clear, therefore, that the measurement of radioactivity in rocks in the field as well as in samples in the laboratory has become a method of geophysical exploration of some importance. If we consider the recent technological advances in the general fields of nuclear physics and electronics it seems proper to review the present status of the methods and procedures of radiological exploration. General Considerations Equilibrium If we take a fixed amount of uranium that has just been purified, some of it will immediately start decaying into its first daughter element which in turn decays into its own daughter and so on down the line until the last daughter is reached—a stable isotope of lead. The rate at which a radioactive element decays is frequently expressed as the half-life, which is the length of time required for the decay of half the atoms in a given amount. The half-life is inversely proportional to the decay constanl X which is defined as the number of atoms which decay in one unit of time divided by

Jan 1, 1949

By Henry Faul

Measurement of radioactivity of rocks and ores has developed into a complete method of geophysical exploration. The problem falls into three natural categories: (1) surface radiation measurement in the field and underground; (2) radioactivity logging of drillholes; and (3) laboratory analysis of samples. Portable counters are used in the field for tracing radioactive formations and for quanti tative estimates of radioactive content of surface rock. Wartime advances in battery design make it possible to construct small precision counters that can be carried easily. Even the smallest conventional diamond drillholes can be logged, and actual content of the radioactive element can be measured. The exact grade of very thin active layers or veins can be estimated only approximately. Samples may be analyzed for their alpha, beta or gamma activity, and beta assaying is the best suited to rapid routine operation. Simple calibration with standard samples is sufficient for rough work, but a density correction is necessary when greater precision is required. Samples with high emanating power should be fixed and stored for three weeks to reestablish the radium-radon equilibrium prior to precision assaying. Carno-tite can be fixed by sintering or molding with plastics. Among the important new developments, a low-voltage Geiger tube has been 'designed recently, and crystal scintillation counters hold great promise for high-efficiency gamma-ray measurement. Introduction During the last few years we have witnessed an unprecedented rise in the demand for radioactive minerals, coming as a direct consequence of the discovery of nuclear fission and subsequent developments, the full impact of which is by no means in sight even now. It remains certain, however, that radioactive minerals, and especially those which can be used as ores of uranium and thorium, will continue to be of great interest not only to the prospector and mine operator but also to the various inspection parties envisioned by most of the schemes advanced for the control of nuclear energy on a world-wide basis. It is clear, therefore, that the measurement of radioactivity in rocks in the field as well as in samples in the laboratory has become a method of geophysical exploration of some importance. If we consider the recent technological advances in the general fields of nuclear physics and electronics it seems proper to review the present status of the methods and procedures of radiological exploration. General Considerations Equilibrium If we take a fixed amount of uranium that has just been purified, some of it will immediately start decaying into its first daughter element which in turn decays into its own daughter and so on down the line until the last daughter is reached—a stable isotope of lead. The rate at which a radioactive element decays is frequently expressed as the half-life, which is the length of time required for the decay of half the atoms in a given amount. The half-life is inversely proportional to the decay constanl X which is defined as the number of atoms which decay in one unit of time divided by

Jan 1, 1949

By W. Rostoker, A. S. Yamamoto, K. Anderko

ALTHOUGH the corrosion resistance of magnesium and its alloys is closely related to iron content, there has been no direct measurement of the solid solubility of iron in magnesium. Bulian and Fahrenhors;1 and Mitchel]2 agree that pure iron or a limited terminal solid solution crystallizes from the Mg-rich liquid. For this reason a magnetic-moment method was selected to estimate that portion of the total iron content which is not in solid solution. Since iron in solid solution in magnesium cannot contribute to ferromagnetism, the difference between chemical and magnetic-iron analyses should yield the solid solubility. By experimentation it was found that the melting of pure sublimed magnesium (99.995 wt pet purity) in Armco-iron crucibles at about 800°C is a convenient way to introduce small amounts of iron. Melts retained 5, 10 and 20 min at 800°C analyzed 0.003,, 0.005,, and 0.018 & 0.001 weight pet Fe, respectively, after being stirred, heated to 850°C, and cast into graphite molds. The as-cast alloys were pickled in acid (dilute HC1 + HNO3), annealed at 600°C for 3 days, scalped on a lathe to remove the pitted surface, pickled again, extruded at about 100°C to 3-mm wire, reannealed 41/2 days at 500°C, and water-quenched. The specimens were again scalped, pickled, and used both for chemical and for magnetic analysis. Most of the precautions described were intended to prevent iron pickup by contact with tools or superficial iron enrichment by volatilization of magnesium during heat-treatment. It is believed that the specimens ultimately used for test were homogeneous and characteristic of phase equilibria at 500°C. Magnetic Analyses A susceptibility apparatus of the Curie type was used for magnetic analyses. Field strengths of up to 10,400 oersteds could be generated. By this method, an analytical balance measures the force of attraction which a calibrated magnetic field exerts on a suspended specimen. The force equation is as follows f/m = M dh/dy where f/m = force per unit mass of sample M = magnetic moment per unit mass dH/dy = magnetic field gradient The dH/dy characteristic of the instrument is determined by the use of a standard palladium sample, and the calibration is made independently for all values of H. Since a large finite field is required to saturate an assembly of ferromagnets, it is necessary to measure the apparent magnetic moment for increasing steps of H until a saturation value is obtained. The percentage of iron in the sample as free ferromagnetic iron may then be computed simply C= 100 (M1/M1) where C = percent content of undissolved iron in sample M1 = saturation magnetic moment of sample per unit mass M1 = saturation magnetic moment of iron per unit mass taken as 217 emu-cm per gm There is no serious difficulty in applying this method except for the unusual magnetic behavior of very fine particles of ferromagnetic substances. It has been found and is the basis for a widely accepted theory that with sufficient subdivision, the magnetic fields required to saturate and the coercive force after saturation rise to exceedingly high values. Recent work on precipitates of Fe and Co from copper solid solutions8 showed that about 5000 oersteds were necessary to approach saturation. The magnetic moments as a function of field strength measured in the present investigation are listed in Table I. Only the 0.018 wt pet Fe alloy yielded a magnetization curve with a fairly well-defined saturation plateau at 3.76x10 -2 emu-cm/ gm. This corresponds to 0.017 & 0.001 wt pet Fe in the alloy. This indicates that the solid solubility must be of the order of 0.001 wt pet Fe. The magnetic-moment data of the other two alloys are badly scattered, indicating that the amount of ferromagnetic iron in these samples is so low that the magnetic forces acting on them cannot be measured accurately by the analytical balance used. Nevertheless, the fact that even the 0.003, wt pet Fe alloy shows ferromagnetism indicates that the solid solubility must be below that value. Acknowledgment This work was sponsored by the Pitman-Dunn Laboratory of Frankford Arsenal, Philadelphia, Pa. The support and permission to publish are gratefully acknowledged. References W. Bulian and E. Fahrenhorst: Zeic. Metallkunde, 1942, vol. 34, pp. 116-170. 2 D. W. Mitchell: AIME Transactions, 1948, vol. 175, pp. 570-578. 3 G. Bate, D. Schofield, and W. Sucksmith: Philosophical Magnsine, 1955, vol. 46, pp. 621-631.

Jan 1, 1959

By N. G. W., Cook

When an excavation is made underground the original rock stresses are removed from the surfaces of the excavation. These surfaces converge to partially close the excavation and the superincumbent rock mass moves down towards the excavation. If the convergence of the surfaces of the excavation were controlled, energy generated by their motion against the controlling forces could be extracted. Since the total forces in the rock mass are not significantly affected by the excavation, stress concentrations arise around the excavation, which compensate exactly for those stresses no longer transmitted through the excavation. These phenomena give rise to two general principles which provide the basis for analyzing the effects of making any underground excavation. The first of these is that the total force resulting from the stresses across any plane in the rock, including any plane through the excavation, must be the same before and after the excavation is made. The second of these is that energy must necessarily be released as a result of making an underground excavation.

Jan 1, 1969

By William N. Poundstone

To forecast the future of coal intelligently, one must first consider the market outlook. Coal can be used for many purposes, but currently about 25% of it goes into metallurgical coke, while 75% serves as fuel. Coal for metallurgical coke should show a modest growth for at least the next decade, primarily because of increased exports, but the important factor in the coal outlook is energy. Today, this country faces a serious shortage of energy, and its requirements are growing at an almost unbelievable rate. Last year the United States consumed 68 quadrillion Btu, or double the energy it consumed in 1950, and, if projections are correct, this figure will grow to 150 quadrillion Btu by 1990. Thus, in one working lifetime, the nation's energy consumption is expected to increase by roughly five times. The future of coal hinges on its degree of participation in meeting this energy need. The Federal Power Commission predicts that coal consumed by electric utilities will increase about 4-576 per yr, reaching 472 million tons by 1980 and 615 million tons by 1990. If this projection proves correct, 1980 consumption will be double that of last year and, even more startling, the utility industry alone will use more coal in 1990 than the entire coal industry produced in 1970. This is a tremendous increase, but in view of the projected energy growth, it is difficult to see how this country's needs can be satisfied with- out a coal contribution of this magnitude. Unless some new source such as solar energy is discovered, it must be assumed that the projected energy will come principally from the present-day sources-oil, gas, nuclear materials and coal.

Jan 1, 1971

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Jan 1, 1938

By U. N. Bhrany, N. Arbiter

Over the last one hundred years the problem of assessing the efficiency of energy consumption in producing rock breakage has been studied by many investigators from a variety of viewpoints. Their contributions fall into three main categories: (1) those characterized by a priori assumptions of a relation between the energy required for fracture and the degree of fragmentation produced (e.g. Rittinged(l), Kick(2) Bond(3)); (2) those studying simple systems with controlled energy applications (Gross(4)?(5) ); (3) those treating operating data to develop practical relative measures of efficiency (Coghill(6), Taggart(7)). Closely involved in the efficiency problem is the characterization of size distributions produced by comminution. Unless an experimental size distribution can be approximated by a distribution function and its constants, it becomes difficult if not impossible to develop quantitative energy-particle size relationships. While many such functions have been proposed, none are both completely adequate and convenient. The simpler fonns usually describe only a part of the sizing data, while those which apply to a greater extent are cumbersome(8). The thesis underlying the study here reported can be stated as follows: Size reduction in a tumbling mill subjects ore particles to a relatively constant fracture-producing environment. The intensity of the forces is determined by such factors as the mass of the breaking bodies (rods, balls, rock), and the speed and dimensions of the shell. For a particular ore the extent of size reduction will depend both on the intensity and on the duration of exposure. The latter is the residence time in a batch mill, or is determined by the effective volume and the flow rate in a continuous mill. Size reduction can thus be regarded as a rate process in which the weight of material in size intervals varies as a function of grinding time. Although both the rates of disappearance of coarser sizes and

Jan 1, 1961

By Norman F. Schulz, Emert W. Lindroos, Strathmore R. B. Cooke

DURING the course of an investigation of the effects of various starch products on hematite and quartz in regard to their separation by flotation, it was found that whereas most starches flocculated suspensions of hematite in water, they did not flocculate similar suspensions of quartz. However, a derivative of whole corn starch containing approximately one tenth aminoethyl group (-—CH,CH2NH2) per glucose unit proved to be an exception. This aminoethyl starch was a very good flocculant for both hematite and quartz, and also possessed the property of depressing both minerals in cationic flotation tests. In view of the widespread use of starch as a flocculating agent of solids in tailing water, pulps, and for coal slimes, ore and various other purposes in sulphide and nonsulphide flotation, attention is called to the effective surface activity of aminoethyl starch in flocculating suspensions of the two minerals investigated. Test Materials The starch products employed included Globe Pearl starch No. 144 and fresh aminoethyl starch, both supplied by the Corn Products Refining Co. Dr. A. L. Elder" has kindly furnished a description The minerals used in the various tests are listed in Table I. Their specific surfaces were determined by the air permeability method, which gave results reproducible to within plus or minus 3 pct. Surface areas obtained by krypton adsorption were greater than the air permeability values by a factor of 2.0 for quartz and 62.4 for hematite. Starch Adsorption on Mineral Surfaces Starch adsorption data were obtained by agitating for 1 hr measured volumes of neutral starch solutions of known concentrations with weighed quantities of finely divided mineral of measured specific surface. The mineral then was separated from the pulp liquor by centrifugation and the residual starch content determined by chemical analysis. The analytical procedure consisted of oxidizing the starch with an excess of dichromate in acid medium at elevated temperature and titrating the excess dichromate by the ferrous ammonium sulphate—potassium permanganate method. Analytical results were reproducible to within less than 1 pct. Adsorption data obtained in unbuffered solutions near the neutral point are plotted in Fig. 1. The adsorption on either mineral was far greater for the aminoethyl starch than for the Pearl starch. Flocculation The degree of flocculation was determined for a given pulp by measuring the time required for the supernatant liquid to reach a certain degree of clarity. This was accomplished by passing a standard light beam through the pulp, contained in a glass settling tube, and measuring the time required after agitation ceased for the intensity of the transmitted beam to reach a predetermined value. Starch reagent was added to each pulp in small uniform increments, and the settling time was determined after each such addition. Increase in pulp liquor volume due to the added starch reagent was ignored in these tests. Pulps were maintained at or near neutrality. of the preparation of the aminoethyl starch: "Three hundred and sixty grams of powdered unmodified corn starch was slurried in 3 liters of water and stirred during gelatinization. Eighty-six grams of ethylenimine was added slowly during reflux which was continued for 4 hr. The yellow solution set to a gel upon cooling. This was broken up and neutralized with HC1. The thick paste was dried on hot rolls. Adsorbed polyethylenimine and salts were removed from the yellowish products by washing first with acidified aqueous '60 per cent' alcohol. The white product contained nitrogen corresponding to about one aminoethoxy group per ten glucose residues." Only laboratory samples of this starch derivative have been prepared. The starch reagents for use in flocculation, flotation, and adsorption tests were made up by dispersing the appropriate quantities of air-dry starch in cold water, adding boiling water, and heating for 30 min at 120°C under pressure. When used ip adsorption tests, the starch solutions first were cleared of insoluble matter by centrifugation.

Jan 1, 1953