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By Warren W. Jamar, Philip D. Pearson

IN recent years, there have been many changes in mining operations in the Lake Superior district. To follow these trends on the Menominee Range of Michigan, information has been assembled from all of the iron informatior]mining operations in the area. There are 15 operating underground mines in the Iron River-Crystal Falls area of the Menominee Range. Within the past two years, two idle properties were reopened pasttwoyears,and are now producing, and a third and fourth are being reopened. Also, there are two siliceous openpits operated by independent companies outside this immediate area. Six companies operate the underground mines, employing some 1850 employees. Table I shows pertinent facts about these properties. During 1949, the largest mine in Iron County shipped 571,287 tons, and one of the newer mines shipped 39,378 tons, with a range total to 3,535,-373 tons. Since the Menominee Range was opened in the 1870's, the mines in Iron County have shipped 85,890,922 tons. From an operator's viewpoint rather than a geologist's, the ore is' classified as semi-hard, composed of hematite and limonite. It is not as soft as the ores of the Marquette Range nor is it as hard as the hard ores of the Marquette and Vermillion Ranges. The ore bodies have slate hanging walls and slate footwalls. In most cases the hanging walls and footwalls are soft and high in sulphur. The sulphur comes from pyrite, and these slates will ignite when piled more than 6 to 8 ft high. Ore is mined on this range by: 1—Sub-level stop-ing; 2—Shrinkage stoping; 3—Sub-level caving; 4— Block caving; 5—Top slicing. The predominance of these methods is in the order named. Underground drilling is important in the mining cycle. Some changes made and trends toward future changes fall into four categories: Drill bits, drill steel, drill machines, and compressed air pressures. Several types of bits have been tried and are in use. They include the detachable tungsten carbide, insert bit; the intraset steel bit, which is a conventional steel rod with tungsten carbide insert; the one-use bit; and the multiple-use bit. For many years, detachable multiple-use bits have been standard. In tests conducted recently to im- prove drilling efficiency, this bit was used as the basis for comparison. Under existing conditions, a multiple-use bit can be resharpened about three times before it is discarded. A thorough test of 2-in. tungsten carbide threaded bits was conducted under various ground conditions. 1—The drilled footage ranged from 48 to 600 ft per bit; averaging 357 ft per bit. Under these same conditions, a multiple-use bit ranged from 8 to 80 ft per bit. 2—The bit cost was greater for the insert bit in each case. 3—The average drilling speed for the insert bit was 12 in. in 62 sec and for the multiple-use bit was 12 in. in 64 sec. In a second test, 2V4 -in. tungsten carbide bits with the large 1 3/16-in. thread were used in moderately soft ground on a 152-lb drifting drill on a long feed jumbo. 1—The drilled footage ranged from 450 to 5000 ft per bit, averaging 1810 ft per bit. Under these same conditions, a multiple-use bit averaged 64 ft per bit. 2—The bit cost was reduced by the use of the insert bit. 3—No increase in drilling speed was recorded. 4—Minimum footage obtained was caused by thread failure. To improve the thread life, thread size on the rod was increased and the bit was attached to the rod with a pipe wrench. After this, bits failed in equal proportions because of cracked skirts, broken inserts, and gage loss. Tungsten carbide bits are now used in the operation where this second test was conducted because labor costs were lowered as a result of reducing the number of bits being changed by the miners. At the same operation and under the same conditions as the second test, 1Y4-in. insert bits with standard 1-in. threads were used. These bits did not drill much more than 300 ft before thread failure and were then welded to the rods and used until total failure. Sometimes this footage was considerable, sometimes it was not. Chisel-type 2%-in. insert bits were

Jan 1, 1952

By Raymond J. Kujawa

For general purposes, insulating materials may be any of those mineral substances that provide a barrier between a desired human environmental feature and an unwanted condition. In this sense, radiation shields, electrical insulations, cryogenic insulation, and acoustical barriers would qualify. For this chapter only the thermal and acoustic insulations used for the median range of normal comfort control will be covered. Because of their magnitude and complexity the other fields are left to other chapters. In another sense, this section deals only with the ultra-lightweight aggregates and insulations, rather than the multitude of light-weight structural materials. Definitions and Uses The insulating materials covered in this chapter are the three groups of mineral products that provide thermal or acoustic barriers through the median temperatures encountered in home and industry. The three mineral categories are perlite, vermiculite, and the silicate wools whether they be categorized as glass, mineral, or rock. Perlites are those amorphous aluminum silicates with minor impurities that take the form of a felsitic, glassy lava possessing a pearl-like luster and concentric cracking. In a more commercial sense the term is used to describe either the natural or processed acidic, volcanic glass, containing from 2 to 5% combined water, that may be converted to a frothy mass by heating rapidly to the softening point. Vermiculites are micaceous, hydrated magnesium iron aluminum sheet silicates of varying composition. Commercial vermiculites are any of these sheet silicates that are capable of sufficient expansion on rapid heating to make an acceptable, highly porous product. Mineral wools, rock wools, silicate cottons, glass fiber are generic names for manufactured fibers in which the fiber forming substance may be slag, certain rocks, or glass. The fibers may be made by a blowing or spinning process. The resultant fibers may be felted or matted or gathered in the manner best suited to the use. The three groups may be used competitively to insulate ceilings and walls. The fibers have strong advantages in this area as they may be manufactured in batts that are stable in residential wall construction. The perlites and vermiculites are more suited to insulate cores and cavities of masonry walls and as plaster and concrete aggregates for thermal insulations. Vermiculite is widely used for insulating attic floors. Because of manufacturing techniques and controls, the glass fibers have made great strides as composites in the plastics industry but only a few of these uses classify in the insulation category.

Jan 1, 1975

JESSE L. JONES,* Pittsburgh, Pa. (written discussion?).-The most important criterion on which judgment of the quality of manganese bronze can be based is its freedom from lead. Not over 0.03 per cent. of lead should be present in a good grade of manganese bronze. While it is not questioned that manganese bronze with a high tensile strength and considerable ductility can be made .from materials that will give a lead content of possibly 2 to 3 per cent., there is no doubt that such material, while it may machine readily, will be found to withstand the impact test very poorly, and hence be unsuited for high-grade engineering work. When lead is present in considerable amounts, it forms in small pools in the alloy and the material has little strength at these points; in fact, such spots in the metal are equivalent to nicks in a test bar as far as their effect on tensile strength is concerned. A further objection to a high lead content is the ease with which it oxidizes and its consequent tendency to produce dross. A second characteristic of a high-grade manganese bronze is a low content of manganese. This should not exceed 0.05 per cent.; in fact, very many of the best grades of manganese bronze show, on analysis, only a trace of manganese or no manganese whatever. Manganese is a deoxidizer and its ready oxidation protects the other metals of the alloy; but if it is present in large amounts it will produce considerable manganese dioxide, which does not separate readily from the molten alloy and may produce black specks or drossy spots and render the obtaining of clean castings difficult. Aluminum should be present in a good grade of manganese bronze in only very small amounts. A content of 0.10 per cent. aluminum is ample. Larger amounts have a tendency to increase the shrinkage of the alloy, to give the ingots and castings a white, scruffy appearance, and to prevent the beautiful, golden, oxidization color characteristic of high-grade manganese bronze and a most excellent indication of quality. The work that the author of the paper has done is valuable from a con- servation standpoint, and it will supplement, in a marked degree, the advances that have been made by a number of manufacturers of manganese bronze in utilizing the turnings from this material. A number of firms have succeeded in making a very good grade of ingot metal from turnings and other light scrap, obtaining a tensile strength and elongation

Jan 4, 1919

WALTER N. CRAFTS,* Toronto, Canada (written discussion?).-During the forging of 9.2-in. shells -for the United States Army, it was noticed that better results were obtained in certain instances when test bars had been held sometime before pulling. An investigation, therefore, was made by our metallographer, Mr. F. M. Arnold, to determine the effect of seasoning. The forging consists of a single operation, piercing a solid cast blank. The test sections were cut from the walls by an oxyacetylene flame, one piece from the nose end and one from the base on the opposite side. The test pieces were not heat treated in any way and the tests and seasonings were carried on at normal atmospheric temperatures. The specifica-tions were as follows: Standard 2-in. test bar, 0.505 in. in diameter; elastic limit, over 19 long tons, or 42,500 lb.; ultimate stress, 39.6 to 49.1 long tons, or 87,500 to 110,000 lb. per sq. in.; elongation, over 13 per cent. As a preliminary test two heats were selected; BP555, which was tested and reported failed on elongation on Aug. 20; and B01771, which was tested and reported failed on Aug. 24. On Aug. 29, retests were cut and machined from the same shells and held till Sept. 3 (5 days) when they were pulled. Both sets of results are given below.

Jan 12, 1919

By Robert F. Mehl

EXTENSION of physical and chemical methods of research in the study of metallic behavior continues rapidly, particularly in the correlation of behavior with crystal structure, and in the analysis of elastic and plastic properties. The growth of the science of metals during 1933 calls for special comment; the need for special reviews and for textbooks and monographs is now acute, as might he supposed from the number of references appended to this article, a list which is much abbreviated.

Jan 1, 1934

By A. H. Larson, R. J. McClincy

ALTHOUGH arsenic has a very high vapor pressure and vacuum distillation appears to be a likely method for its removal from lead, the published literature contains virtually no information concerning the vacuum removal of arsenic from lead. Caldwell, Spendlove, and St. Claire1 mention arsenic in their investigation of the removal of volatile metals from lead by vacuum distillation. They do not, however, give any data for arsenic removal or refer to any actual experimental work involving arsenic dissolved in lead. Moriyama, Kozuka, and Miura2 have determined the activity of arsenic in dilute As-Pb alloys in the temperature range from 450" to 600°C using a closed galvanic cell. They found that the activities of both arsenic and lead showed a positive deviation from ideality at 600°C. In view of the lack of experimental data regarding the vaporization of arsenic from As-Pb alloys, a limited vapor pressure study was made on liquid alloys containing from 0.5 to 3.3 wt pct As in lead at 703°C. The pressure of As4(v) above the alloys studied was determined from weight-loss data collected by means of the inert-gas saturation method. The experimental apparatus and procedure used were similar to that discussed by Alcock and Hooper9 with modifications as described by the authors., The technique involved was one of passing a known volume of inert gas over the alloy to be studied in a known amount of time and determining the loss in weight of the sample. Because of the low vapor pressure of lead at 703"C, the observed weight loss could be attributed solely to the vaporization of arsenic as the tetratomic molecule AS43 Measurements of the apparent vapor pressure were repeated at different inert-gas flow rates until from three to five values were obtained which were independent of inert-gas flow rate. This value of the apparent vapor pressure was taken to be the equilibrium vapor pressure of the alloy under consideration. The vapor pressures measured in this investigation have been converted to the activities of arsenic in As-Pb alloys, Table I, by use of the data compiled by Elliott and Gleiser5 for the vapor pressure of pure arsenic. The standard state for arsenic was chosen as the pure, hypothetical, supercooled liquid. The activity of arsenic was calculated from the fourth root of the ratio PAs,/PAS,. The low magnitude of the vapor pressures given in Table I explains the difficulty en- countered by earlier workers in successfully vacuum distilling arsenic from very dilute As-Pb alloys. The data shown in Fig. 1 indicate that the As-Pb system behaves ideally. The apparent outlier represented by the alloy containing 1.43 mol pct As is a result of the fact that the pressure of As, above the alloy was barely detectable by the experimental procedure used in this investigation. Because of this, the apparent vapor pressure determined for this alloy could be in considerable error. Moriyama, Kozuka, and ~iura' have reported that arsenic shows a positive deviation from ideality in dilute solution in lead. However, details of their results have not been made available. This research was made possible by a grant from the National Science Foundation (GK-196) for which the authors are very appreciative.

Jan 1, 1970

By L. C. Morganroth

Magnesite both Massive and Crystalline MAGNESITES are. of two general classes-massive and crystalline. Massive magnesite occurs in serpentine, being formed by the breaking down or decay of serpentine-making minerals or rocks as olivine, etc. (All the magnesia contained by the olivine is not liberated, as a portion goes to make up the serpentine; the breaking up of this serpentine later forms more magnesite.) Serpentine in various stages of transformation is found in the vicinity of magnesite deposits. Massive magnesite is very widely distributed. It is found in Greece, . California, Africa, India, Australia, Mexico, South America, and deposits of varying sizes occur in several of the European countries. Those on the Island of Euboea, Greece, are probable the most important deposits of this character of magnesite. They have been worked for a number of years, the principal quarries or mines being 3 miles in the interior from the village of St. George. (St. George is on the west coast of the island, between the towns of Limni and Khalkis.) (Figs. 1 and 2). -The magnesite occurs in veins or lenses in serpentine. Some of these lenses are very large; one worked several years ago was approximately, 50 ft. in thickness, 75 to 100 ft. high and 300 ft. or more in length. The magnesite is pure white and makes a very prominent feature of the landscape. While massive magnesite is widely scattered over the world, many of the deposits are in veins too thin to work. The usual mode of occurrence is in the form of stock work, the deposits in Venezuela, Mexico, and many of those in California, being of this form. The veins vary in thickness from the thinness of paper up to several inches, running in all directions, occasionally leading to a mass or nucleus of some,size. The spaces between the veins are filled with a disintegrated serpentine in the form of sand. Several of the deposits in California would probably be workable, if they were more favorably situated with reference to transportation, but by far the majority of the deposits are too poor to work. At one deposit,

Jan 9, 1914

By M. H. Waxman, M. Gondouin, H. J. Hill

Streaming-potential experiments were conducted within the Muddy- and Dakota-sandstone interval of a Denver basin well. Analysis of the data shows that, for this case, streaming potentials opposite sands were higher than those opposite shales when the mud was fresh. Streaming potentials opposite shales, however, were of sufficient magniiIlde to be important in SP interpretation. They were linearly dependent upon pressure differential, and they increased with mud filtrate resistivity. The magnitude of streaming potentials opposite sands was influenced by the characteristics of the original mud cake formed at the time of drilling. Use of mud samples taken at the time of logging may not always be satisfactory for determining streaming-potential corrections. Both the streaming and electrochemical potentials were found to be affected by the previous history of the borehole system. Following a change in mud characteristics, several days were required for SP stabilization. This was, in part, due to the mud cake acting as an imperfect shale membrane. INTRODUCTION Laboratory investigations by Wyllie,1 Salisch,2 Moore," Sen Gupta and Bannerjee,0 and Hill and Anderson' have shown that streaming potentials developed across mud cakes deposited on permeable filter beds are of sufficient magnitude to be critically important in SP interpretation. Streaming potentials across shales have been reported by Schenck,' Gondouin and Scala; and Hill and Anderson." The magnitude of the shale streaming potentials obtained by Schenck and by Gondouin et a1 led these authors to conclude that in many cases the shale streaming potential would approximately equal the mud-cake streaming potential. Hill and Anderson, however, obtained somewhat lower magnitudes of shale streaming potential. The field experiment described in the present paper was a cooperative project carried out by the respective operations and research departments of Schlumberger Well Surveying Corp., Shell Development Co. and Shell Oil Co. The primary objective of the experiment was to determine in the borehole the streaming-potential behavior of both shales and mud cakes under conditions approaching, as nearly as possible, those normally encountered in logging practice. METHODS AND EQUIPMENT WELL A Muddy- and Dakota-sandstone vie11 in the Denver basin was chosen for the experiment. Both sandstones were water-bearing and, since reservoir pressures in these sandstones are abnormally low (gradient of approximately 0.25 psi/ft), it was expected that studies of streaming potential could be conducted from low-pressure differentials (approximately 200 psi) to about 27000 psi by bailing mud from the hole, filling up and then applying wellhead pressure. The selected well encountered the Muddy sand-

By Shiou-Chuan Sun

THERE are several postulations for the mechanism of slime-coating. Ince1 proposed the electrostatic hypothesis, del Giudice2 suggested the chemical theory; Bankoff3 reported that slime-coating is inhibited whenever the surfaces of the slime particles are ionized sufficiently for Brownian movement to occur, and is facilitated when they are not. These postulations were examined by experiments involving the Burton tube, the cataphoretic cell, and slime-coating. The techniques involved will be described elsewhere in this paper. The electrostatic hypothesis, supported by migration experiments in a Burton tube, was abandoned by del Giudice.2 Experiments of mineral migration in a Burton tube, after the idea of Ince with modification, indicated that this apparatus was inefficient for accurate observation. A cataphoretic cell was constructed. The experimental data, as shown in this paper, enable the correlation and advancing of this hypothesis. Del Giudice's chemical hypothesis considered that slime particles are attached to the galena surfaces by a cement formed as the result of a metathetical reaction between the sulphide and the slime particles. Applying this hypothesis, the calcite slime particles were cemented to the galena surface by the formation of a cementing lead carbonate. In a similar way, lead silicate was considered as the cement of quartz slime coating on galena. Experiments verifying this hypothesis were carried out according to the following procedure: Fresh mineral particles selected from the central part of the broken lumps and examined first under a microscope for ascertaining a clean surface were placed in a small beaker (1.5-in. dia. by 2.5 in. deep) half filled with one kind of slime pulp. The dilution of all slime pulp was 4: 1 and the particle size of slime was minus 400-mesh. After agitation for 5 min. the specimen was removed by a sharp-end tong and washed gently three times in three separate distilled water baths. It was dried before a small electrical fan and examined immediately under a microscope. A photograph was made of the observation. With reference to the published solubilities,4 several of these experiments, which contradict the chemical hypothesis, are listed as following: I. The coating of fluorite slime on the galena surface was light but the coating of galena slime on the fluorite surface was heavy. In a similar way, the coating of quartz slime on the galena was fairly light, but the coating of galena slime on the quartz particle was heavy. According to the chemical hypothesis, using the same constituents and regardless of which is the slime, the density of the coating should be expected to be the same. This, however, as shown above, is not true. Moreover, fluorite (CaF2), having a solubility of 16 mg.[4a] per liter of water, should not be

Jan 1, 1943

By Shiou-Chuan Sun

There are several postulations for the mechanism of slime-coating. Incel proposed the electrostatic hypothesis, del Giudice2 suggested the chemical theory; Bankoff3 reported that slime-coating is inhibited whenever the surfaces of the slime particles are ionized sufficiently for Brownian movement to occur, and is facilitated when they are not. These postulations were examined by experiments involving the Burton tube, the cataphoretic cell, and slime-coating. The techniques involved will be described elsewhere in this paper. The electrostatic hypothesis, supported by migration experiments in a Burton tube, was abandoned by del Giudice.2 Experiments of mineral migration in a Burton tube. after the idea of Ince with modification, indicated that this apparatus was inefficient for accurate observation. A cataphoretic cell was constructed. The experimental data, as shown in this paper, enable the correlation and advancing of this hypothesis. Del Giudice's chemical hypothesis considered that slime particles are attached to the galena surfaces by a cement formed as the result of a metathetical reaction between the sulphide and the slime particles. Applying this hypothesis, the calcite slime particles were cemented to the galena surface by the formation of a cementing lead carbonate. In a similar way, lead silicate was considered as the cement of quartz slime coating on galena. Experiments verifying this hypothesis were carried out according to the following procedure: Fresh mineral particles selected from the central part of the broken lumps and examined first under a microscope for ascertaining a clean surface were placed in a small beaker (1.5-in. dia. by 2.5 in. deep) half filled with one kind of slime pulp. The dilution of all slime pulp was 4:I and the particle size of slime was minus 400-mesh. After agitation for 5 min. the specimen was removed by a sharp-end tong and washed gently three times in three separate distilled water baths. It was dried before a small electrical fan and examined immediately under a microscope. A photograph was made of the observation. With reference to the published solubilities,' several of these experiments, which contradict the chemical hypothesis, are listed as following: I. The coating of fluorite slime on the galena surface was light but the coating of galena slime on the fluorite surface was heavy. In a similar way, the coating of quartz slime on the galena was fairly light, but the coating of galena slime on the quartz particle was heavy. According to the chemical hypothesis, using the same constituents and regardless of which is the slime, the density of the coating should be expected to be the same. This, however, as shown above, is not true. Moreover, fluorite (CaF2), having a solubility of 16 mg.4a per liter of water, should not be

Jan 1, 1943

By Shiou-Chuan Sun

There are several postulations for the mechanism of slime-coating. Incel proposed the electrostatic hypothesis, del Giudice2 suggested the chemical theory; Bankoff3 reported that slime-coating is inhibited whenever the surfaces of the slime particles are ionized sufficiently for Brownian movement to occur, and is facilitated when they are not. These postulations were examined by experiments involving the Burton tube, the cataphoretic cell, and slime-coating. The techniques involved will be described elsewhere in this paper. The electrostatic hypothesis, supported by migration experiments in a Burton tube, was abandoned by del Giudice.2 Experiments of mineral migration in a Burton tube. after the idea of Ince with modification, indicated that this apparatus was inefficient for accurate observation. A cataphoretic cell was constructed. The experimental data, as shown in this paper, enable the correlation and advancing of this hypothesis. Del Giudice's chemical hypothesis considered that slime particles are attached to the galena surfaces by a cement formed as the result of a metathetical reaction between the sulphide and the slime particles. Applying this hypothesis, the calcite slime particles were cemented to the galena surface by the formation of a cementing lead carbonate. In a similar way, lead silicate was considered as the cement of quartz slime coating on galena. Experiments verifying this hypothesis were carried out according to the following procedure: Fresh mineral particles selected from the central part of the broken lumps and examined first under a microscope for ascertaining a clean surface were placed in a small beaker (1.5-in. dia. by 2.5 in. deep) half filled with one kind of slime pulp. The dilution of all slime pulp was 4:I and the particle size of slime was minus 400-mesh. After agitation for 5 min. the specimen was removed by a sharp-end tong and washed gently three times in three separate distilled water baths. It was dried before a small electrical fan and examined immediately under a microscope. A photograph was made of the observation. With reference to the published solubilities,' several of these experiments, which contradict the chemical hypothesis, are listed as following: I. The coating of fluorite slime on the galena surface was light but the coating of galena slime on the fluorite surface was heavy. In a similar way, the coating of quartz slime on the galena was fairly light, but the coating of galena slime on the quartz particle was heavy. According to the chemical hypothesis, using the same constituents and regardless of which is the slime, the density of the coating should be expected to be the same. This, however, as shown above, is not true. Moreover, fluorite (CaF2), having a solubility of 16 mg.4a per liter of water, should not be

Jan 1, 1943

By L. D. Jaffe, H. C. Mann, E. L. Reed

The authors have recently published1 evidence that brittle transgranular fracture of polycrystalline metals does not originate at a point and propagate continuously across the material, but rather develops at numerous related points, leading to a series of micro-cracks which subsequently link up. Series of related microcracks were observed in steel specimens broken in fatigue—specifically, at the central portions which broke during the final sudden fracture. Microcracks of the type mentioned have also been reported by Baeyertz, Craig and Bumps'2 in steel broken under impact. % Some micrographs published by Irwin3 may possibly be interpreted as showing discontinuous brittle cracks. This paper presents additional observations of the authors on discontinuous crack propagation under various conditions. Impact Test Specimens The impact test specimens were cut longitudinally from a steel forging containing: The heat treatment consisted of oil quenching in a heavy section from 1600°F and tempering at 1260°F. The resulting yield strength was 78,000 psi, tensile strength 100,000 psi, elongation 20.0 pet in 2 in., and reduction of area 55.0 pet. Standard V-notch Charpy specimens were broken in a 217 ft-lb machine at a striking velocity of 16.8 fps. Energy absorption and fracture appearance of this material in the V-notch Charpy test are plotted as functions of temperature in Fig 1. After test, fractured halves of specimens appearing 0, 40, 80, and 100 pet fibrous (to the unaided eye) were electroplated with nickel, sectioned longitudinally (perpendicular to the notch at its midpoint), polished and etched with Cohen-Hurlich-Jacobson (C-H-J) reagent (picric acid plus Zephiran chloride in ethyl ether)4 or with Vilella reagent (1 pet picric plus 5 pct hydrochloric acid in ethyl alcohol).5 Fig 2 and 3 show cracks near the path of final fracture in the specimen rated 0 pct fibrous. Many of the cracks terminate at the boundaries of ferrite grains, some at boundaries of pre- existing austenite gzains. * A crack often starts near the end of another. Cracks within the same ferrite grains are parallel or approximately parallel in several cases. A large percentage of the cracks are branched. Fig 4 illustrated a group of cracks in the 40 pct fibrous specimen. Branching and parallelism are well marked. No more than three directions of crack have been observed on the polished surface in one ferrite grain. This is consistent with the evidence6 that brittle fracture of ferrite takes place on the cube face crystallographic planes: the {100} planes. The appearance of some cracks suggests that they have passed around a projecting corner of a second ferrite grain by going outside the plane of polish. In Fig 5 cracks in the 80 pet fibrous specimen may be observed. Some of

Jan 1, 1950

By Seymour G. Epstein

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

Jan 1, 1967

By E. C. Wright

The following article is based on observation of college graduates entering the steel industry in technical work made during the Past 25 Years, the first five of which were spent as a college instructor in two engineering schools, and the last 20 in the employ of a large steel company that has hired hundreds of engineering graduates for steel-mill operations. The college graduates encountered during this period have come from many colleges representing schools in Eastern States, Midwestern Universities, many Southern colleges, and many smaller colleges and normal training schools mostly in western Pennsylvania and Ohio. The college training of these students for engineering work naturally has varied widely and the educational qualifications of the entrants have been in many ways different. It was found at an early date that graduates of standard engineering colleges were much more adaptable than graduates in science from nontechnical schools. The engineering students seemed to be more suited to actual work in steel plants and in general were better able to grasp a knowledge of the operations they observed. However, although the graduates of engineering schools have had somewhat better training in physics, mathematics, and engineering, it has been a general and continual observation that most of the students employed have had inadequate training in the fundamental sciences. Since this discussion relates entirely to metallurgical engineers it should be emphasized that students taking metallurgical engineering courses in college seem to be poorly trained in organic chemistry-physics, physical chemistry, thermodynamics, and any higher form of mathematics than simple calculus. It has been noted frequently that young engineers faced with problems in a mill that involve some mathematics generally flounder badly, and that they have little conception of physical chemistry. Another common deficiency lies in the young graduate's lack of knowledge of where to look for the more detailed literature on any subject. He reverts instinctively to some college textbook whose coverage is usually very elementary. It is recommended that such textbooks contain a bibliography of the source literature. and that students be taught to use the original data. Many of the students had had previous courses in college dealing with metallurgical work such as steel melting, metallograhy, etc.r but it was found that their grasp of these subjects was extremely sketchy. It was soon realized that an ordinary engineering graduate could be taught more about steel melting and manufacturing processes in a few weeks in a plant than he could learn in a college course on such subjects. A similar statement may be made regarding the ability of students to conduct laboratory work. Their lack of technique and skill in handling equipment and setting up experiments was soon apparent. It became neces-

Jan 1, 1948

By E. C. Wright

The following article is based on observation of college graduates entering the steel industry in technical work made during the Past 25 Years, the first five of which were spent as a college instructor in two engineering schools, and the last 20 in the employ of a large steel company that has hired hundreds of engineering graduates for steel-mill operations. The college graduates encountered during this period have come from many colleges representing schools in Eastern States, Midwestern Universities, many Southern colleges, and many smaller colleges and normal training schools mostly in western Pennsylvania and Ohio. The college training of these students for engineering work naturally has varied widely and the educational qualifications of the entrants have been in many ways different. It was found at an early date that graduates of standard engineering colleges were much more adaptable than graduates in science from nontechnical schools. The engineering students seemed to be more suited to actual work in steel plants and in general were better able to grasp a knowledge of the operations they observed. However, although the graduates of engineering schools have had somewhat better training in physics, mathematics, and engineering, it has been a general and continual observation that most of the students employed have had inadequate training in the fundamental sciences. Since this discussion relates entirely to metallurgical engineers it should be emphasized that students taking metallurgical engineering courses in college seem to be poorly trained in organic chemistry-physics, physical chemistry, thermodynamics, and any higher form of mathematics than simple calculus. It has been noted frequently that young engineers faced with problems in a mill that involve some mathematics generally flounder badly, and that they have little conception of physical chemistry. Another common deficiency lies in the young graduate's lack of knowledge of where to look for the more detailed literature on any subject. He reverts instinctively to some college textbook whose coverage is usually very elementary. It is recommended that such textbooks contain a bibliography of the source literature. and that students be taught to use the original data. Many of the students had had previous courses in college dealing with metallurgical work such as steel melting, metallograhy, etc.r but it was found that their grasp of these subjects was extremely sketchy. It was soon realized that an ordinary engineering graduate could be taught more about steel melting and manufacturing processes in a few weeks in a plant than he could learn in a college course on such subjects. A similar statement may be made regarding the ability of students to conduct laboratory work. Their lack of technique and skill in handling equipment and setting up experiments was soon apparent. It became neces-

Jan 1, 1948

By Robert R. French

Beneficiation of low-grade nonmetalliferous mineral deposits by electronic color sorting is currently undergoing a period of rapid development. For those deposits in which the specific gravity, strength, soundness, and electric and magnetic properties of the ore and gangue are similar, the possibility of separation by color, reflectivity, or fluorescence offers hope for the utilization of much poorer quality ore than previously thought possible. For those ores in which consistency of color is required or for which a dry process is preferred, the electronic color sorter is particularly adaptable. Tests performed late in 1966 and reported herein are the result of the continued interest in the dry beneficiation of gypsum and the development of higher capacity color sorting machines. The ore used was a discarded fraction that consisted of – 1 ¼ -in, to + 3/8 -in. ore containing 63.1 to 71.4% (average 67.7%) gypsum. This material was contaminated by various amounts of both carbonate rock and shale, but no pretreatment was performed other than screening to closer size limits before electronic color sorting.

Jan 4, 1969

By E. J. MCOAUSTLAND

THE behavior of steel after overstrain and at moderate temperatures is fairly well known. It has been made the subject of much investigation, and our knowledge is clear and definite on many points. The ultimate raising of the elastic limit, after moderate overstrain, and the consequent lowering of the ductility, seem to be well established. It is also well understood that the immediate effect of overstrain is to lower the elastic limit, possibly to zero, but that if not interfered with, this limit will subsequently rise higher than before. The "tests after moderate temperature," reported in this paper, were undertaken to verify the above statements for the particular steel under investigation, and also to determine, if possible, the total time required for complete recovery from this state of overstrain. The behavior of overstrained steel at temperatures at or below 32° F. is not so well known. Tests made by Prof E. G. Coker, at McGill University,' show that steel, overstrained and subjected to cold, will remain in a state of overstrain for an indefinite period. I am not aware of any other published results of tests along this particular line. The effect of time and temperature on the recovery of steel from overstrain was made in 1902-3 the subject of sortie investigation in the laboratories of the College of Civil Engineering of Cornell University. A general plan was outlined in connection with the regular courses of instruction in testing of materials; but the press of routine work and the demands of the schedules on the time of the students were so great as to presage long delay in the completion of the work. Not much had been accomplished up to 1904-05, when Messrs. E. C.

May 1, 1906

By S. A. Braley

DRAINAGE water from coal mines is probably the most serious water pollution problem today, varying in importance according to location of the mines and geological structure. Drainage may be either acid or alkaline in character. Acid discharge, the most severely detrimental to a stream, is caused by natural oxidation of the sulfuritic material (FeS2) in the strata associated with the coal seam. Since the acid is the result of a natural reaction the acid water differs because it does not cease with abandonment of the mining operations. There is no known economical method of neutralizing acid mine water or any practical method to prevent oxidation of exposed pyrite. Since production of acid from a mine does not stop when mining stops, the total quantity produced depends entirely upon the excavated areas. The increasing volume of acid water in manv mines has greatly increased operating costs. Pumping is expensive and acid mine waters are destructive of all equipment, especially metals in pumps and piping, and necessitate the use of corrosion-resistant materials. Discharge of the acid mine drainage into streams neutralizes their normal alkalinity, causes them to become acid, and produces an environment unfavorable for aquatic life and unsuited for industrial or domestic use without costly treatment. Mine drainages vary in percentage composition over wide limits, although the usual dissolved substances are ferrous and ferric iron, aluminum, calcium and magnesium sulfates, and lesser amounts of sodium, potassium and manganese sulfates and chlorides. Some alkaline discharges may contain heavy concentrations of iron as iron bicarbonate. These waters may produce iron hydroxide deposits in the receiving stream but do not cause it to become acid. In the extensive literature on acid mine water there appears to be a great deal of confusion about the importance of various components and the methods for their determination. In many instances faulty conclusions have been drawn from use of unsuitable methods of analysis. It is desirable that the factors and terms used in evaluation of analyses of mine waters should be so clearly defined that any interested person could properly appraise any analytical report. Some analysts report complete chemical analyses of mine waters and neglect to record drainage volumes. Others report only a minimum of analytical data after taking no precautions to preserve the original composition of the water during the time elapsing between collection and analysis. Some use methods of analysis intended for so-called pure waters of the potable and boiler water classes. These methods are not applicable to highly buffered waters such as mine water. Probably the most common criteria for evaluation are pH, free acidity, or acidity or alkalinity to methyl orange or methyl red, total acidity or acidity to hot phenol-phthalein, and the sulfate content. If these determinations are made on carelessly collected samples after a few days to weeks standing in warm rooms, they do not in any way represent the character of the water flowing from the mines. It is hoped that a brief discussion of the fundamental value of some of these factors may lead to a bettqr understanding of the need for more careful evaluation of mine water discharges. The term pH is one used by chemists to express relative acidity or alkalinity in terms of concentration of effective hydrogen ion in a solution. It is defined as the negative logarithm of the hydrogen ion concentration or activity in equivalents per liter. pH = logarithm A neutral solution, which is one containing the same number of hydrogen and hydroxyl ions, has a pH of 7. As the hydrogen ions increase and the solution becomes more acid, the pH decreases toward zero; and as the hydroxyl ions increase and the solution becomes more alkaline, the pH approaches 14. When dissolved in water to a dilute solution acids like sulfuric and hydrochloric, commonly known as strong acids, ionize completely, and the pH or hydrogen ion concentration varies with molar concentration of the dissolved acid. However, in high concentrations of such acids, the pH or hydrogen ion concentration is less than the acid concentration because the acid does not completely ionize. In only very dilute solutions does the pH represent the total amount of acid that can be neutralized by an alkali. All ionization reactions are equilibrium reactions. If other chemicals are added to the solution of an acid and the added chemical produces an ion that is the same as one of the ions of the acid, the degree of ionization of the acid is altered and the pH changes to some value that represents the active hydrogen ion of the new solution. Thus if iron sulfate is added to a solution of sulfuric acid the pH increases, since the common sulfate ion suppresses the degree of ionization of the sulfuric acid and decreases the effective hydrogen ion. However, the total acidity of the solution is increased. There are two salts composed of iron and sulfate— ferrous and ferric sulfate. In these salts there is no hydrogen ion that can ionize to give an acid solution, but when they are dissolved in water, the pH is less than 7 and the solution becomes acid. This is caused by a reaction known as hydrolysis and is represented by the equations FeSO4 + 2H2O ? Fe(OH)2 + 2H + SO,: or Fe,(SO,)3 + 6H2O ? 2Fe(OH)3 + 6H+ + 3504 A solution with a total acidity of 5000 ppm according to the first equation will have a pH of 4.40 but one with an acidity of 75 ppm, according to the sec-

Jan 1, 1958

By B. Foley

IN THE first report1 disks of steel of known composition and history were exposed, under carefully prescribed conditions, to impacts of explosion products resulting from the explosion of 50-gm. charges of explosives having well-determined rates of detonation, or to impacts of a weight of known mass, falling through measured distances. There were available at the Bureau of Mines Experiment Station five explosives, having rates of detonation of 5716, 4470, 3190, 2296, and 1523 meters per second. It being desired to continue this exposure downward, and no explosives with a lesser rate of detonation being at hand, resort was had to the impact of a falling weight, the differences in the velocity of impact being attained by varying the height from which the weight was allowed to fall. It was expected by this means to demonstrate experimentally that the development of Neumann bands was determined by the suddenness of the deformation of the metal in which they were produced. But while progressive deformations were obtained with the explosive arges, the falling-weight method failed because the tup was ogressively deformed, also the disks were so flattened as to be unfit for metallographic examination. A return, therefore, has been made to the use of explosives as the source of energy, an air-gap being interposed between the charge of explosive and the disk, as the effect diminishes as the function of the distance between the charge and the object on which the products of its explosion, or the shock wave from its detonation, impinge. The details of the arrangement of the tests by the air-gap method were the same as those described by Foley and Howell,2 except that after the system had been set up and the desired apparent specific gravity for the explosive

Jan 2, 1926

By Joachim J. Hauser

Experiments on latent hardening were peyformed by compressing single crystals along a direction perpendicular to the tension axis. The slope and length of easy glide in the tension test were found to depend only on prior deformation in the same slip plane. Prior deformation on a different slip plane changes the stress level of the resulting stress-strain curve. The yield points appearing upon reloading after prior extension and unloading were related to the end of easy glide. SEVERAL researchers have studied the latent hardening due to deformation of a crystal by slip on a slip System after prior deformation. These experiments can be divided into those in which the prior deformation was on the same plane as the subsequent and those in which the two deformation processes were in different planes. In the former category are the experiments of Buckley and Entwistle,1 Parker and washburn,2 and Haasen and Kelly.3 The latter case has not been studied systematically; it was the main purpose of this investigation to produce this type of latent hardening and explain the results in terms of the existing theories of work hardening. In general, tension producing slip on a certain slip system can be preceded by tension, transverse compression or longitudinal compression, each with predictable dislocation movement and intersection. The intersection of dislocations can lead to glissile or sessile jogs, Cottrell-Lomer locks and other sessile dislocations. The effect on the stress-strain curve could depend on which combination of the former mechanisms is operating. Haasen and Kelly3 have studied the yield points which occur in aluminum and nickel single crystals upon reloading after prior unloading in a tension experiment. They attributed this effect to the anchoring of dislocations occurring during unloading. As Cottrell and stokes4 have shown that dislocations cutting through the "forest" could only lead to reversible changes, they attributed the anchoring to the formation of sessile dislocations during unloading. However, different kinds of sessile dislocations could be formed during unloading, and it was the purpose of this experiment to determine whether Cottrell-Lomer locks are responsible for the yield effect and for the end of easy glide. The case where a longitudinal compression is followed by tension along the same axis is commonly referred to as a Bauschinger test. This type of effect was studied by Buckley and Entwistle1 on aluminum single crystals and by Parker and washburn2 on zinc single crystals. In such a test, the tension and the compression activate the same slip plane with opposite slip directions. The use of sideways compression in the present experiments permits the activation of different types of slip systems and the study of their effect on the easy glide region and on the transition between the elastic and easy glide region. The theory of seeger5 for the flow stress in fee materials is applied to explain the latent hardening. EXPERTMENTAL PROCEDURE All the single crystals used in this investigation had an axial orientation close to <210>, called the "0.5" orientation. This is the orientation for which the tensile axis is 45 deg from both the slip plane and the slip direction. The single crystals were grown from the melt under a helium atmosphere using milled graphite boats,=at a rate of 8.6 mm per min. The silver used in the experiment was 99.98 pct pure. The single crystals had a square cross section about 0.9 by 0.9 cm and a length of 14 cm. The orientation of the specimen was determined within ±2 deg by the Laue back-reflection method. The specimens were annealed at 940&apos; ± 2°C in a helium atmosphere for 24 hr and then furnace cooled over a period of 7 hr. The specimens were electropolished in a solution of 9 pct KCN in water. The specimens were tested in a soft-type tensile machine (the load is prescribed) up to 3 pct strain. The stress was increased continuously at approximately 30 g per mm2 per min. The strain was measured over a 5 cm gage length with a mechanical extensometer employing an optical lever. The strain and stress were measured with accuracies of i 2 X 10-5 and ± 2 g per mm2, respectively. The remainder of the stress-strain curve up to 20 pct strain was obtained in a hard-type tensile machine (the strain rate is prescribed). The strain and the stress were measured in that machine with an accuracy of ±2 pct. The compression tests were performed in the hard-type machine using accurately machined steel blocks without lubrication. The blocks were used so as to apply a uniform compression over a length of 13 cm. The strains were measured on the hard-type machine and with a micrometer.

Jan 1, 1962