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By Franklin Moeller

Considering the really short time that has elapsed since hydro-metallurgical processes of extracting copper from ores have been extensively developed, and the large scale on which this method is practised at Ajo, the successful operation of the plant must excite the admiration of every visitor. The application of the mechanical unloader to the purpose for which it is employed at Ajo is but an extension of the use for which it was originally designed, some 20 years ago, for unloading iron-ore vessels at the lower lake ports. At a time when the maximum output of a single machine, with men shoveling the ore into buckets, did not exceed 40 tons per hour, G. H. Hulett invented and constructed a mechanical unloader with a bucket of 10-ton capacity. This machine was of the steam hydrauIic type, and it is still in operation after nearly 20 years of service. Several more machines of the same type were built, but the difficulties of power transmission, and the rapid development of electrical machinery, soon led to the adoption of electrically operated machines, and practically all of the later installations have been thus equipped. This electrically operated unloader has proved so well fitted for the work that the design of the lake boats has been practically revolutionized, with special view to the ease and rapidity of unloading. It is now possible to unload a 12,000-ton vessel with four machines in a little over 2 hr. This has necessitated an increase in the capacity of the machine, and the largest yet built handles an average load of 17 tons, with a possible maximum of 20 to 21 tons. The Ajo excavator is somewhat simpler in design than the iron-ore unloader, in that it is not provided with a larry. In the unloader, the iron ore, picked up by the bucket, is delivered to a larry or transfer car which runs in the lower chord of the bridge; the larry then delivers the ore either into railroad cars, standing on several parallel tracks, or into the stock pile, thereby saving the time that would be required for the bucket to make the trip. At Ajo, the bucket delivers the tailing

Jan 1, 1920

By M. E. Wadsworth, L. H. Raby, A. S. Peck

Infrared spec troscopy was used to study the adsorption of oleate collector on three varieties of hematite. Each of the minerals was found to react with either oleic acid or a solution of sodium oleate to form a mineral cation-collector anion chemisorbed layer at the solid-liquid interface. The chemisorption reaction displaced surface hydroxyls and was found to be pH dependent. The infrared band characteristic of the antisymmetrical C = 0 structural group of chemisorbed oleate appears between 1520 and 1540 cm-'. Evidence is presented which shows that molecular filming of the mineral surfaces with un-dissociated oleic acid precedes chemisorption. Infrared absorbance is correlated with the flotation behavior of the mineral. Adsorption processes are usually classified into two types which are distinguished and character- ized by the nature of the bond formed between the adsorbate and adsorbent. The process in which molecules chemically bond to solid surfaces is termed activated adsorption or chemisorption. If only weak van der Waals forces bind the molecules to the surface then the process is termed physical adsorption. Chemisorption is of primary interest in flotation systems since selectivity may be obtained if a single mineral is rendered air-avid by a specific collector mineral adsorption reaction. In previous studies infrared spectroscopy was used to define the mechanisms involved in the adsorption of oleic acid and sodium oleate on fluorite, barite, and calcite. Infrared techniques were particularly useful since adsorbed monolayers were identified in situ. Further, the infrared method permitted identification of reaction products in the solid, liquid, and vapor phases of the systems. The chemisorption reactions displaced F- from fluorite, SO4 from barite, and CO3 from calcite. This investigation was pursued in an effort to characterize and interpret the adsorption processes for synthetic hematite, compact red hematite, and specular hematite (crystalline hematite). Adsorption tests were performed using either oleic acid or

Jan 1, 1967

By Everett D. Jackson

The largest deposits of chromite in the United States occur in tabular layers in the lower part of the Stillwater Complex, Montana. Nearly 900,000 long tons of chromite concentrates have been produced from mines and mills in this area, and reserves equivalent to more than 2,500,000 long tons of Cr2O3 remain in the ground. Layered concentrations of chromite (known as chromitite zones) occur only within olivine-rich layers of the Peridotite member of the Ultramafic zone of the Stillwater. As many as thirteen chromitite zones, lying conformably one above another, have been found, but only five of them are thick enough to be of any conceivable economic interest, and only two of them have been mined to date. Individual chromitite zones can be recognized by their distinctive internal character and by their stratigraphic position in the Peridotite member. The chemical composition of chromite varies consistently between and within the different chromitite zones. The zones range in thickness from about an inch to more than 12 feet, and the Cr2O3, content of their chromite ranges from 36.6 to 49.2 weight per cent. In any given area, the G chromitite zone is the thickest, but the chromite of the H chromitite zone has the highest grade. Laterally, the thickness of the chromitite zones is related to the thickness of the Peridotite member; in general all are thicker in the eastern part of the Stillwater than in the western part.

Jan 1, 1968

By K. Osseo-Asare

The presence of carbonaceous matter in gold ores presents a two-fold problem: (1) The poor release of gold from the carbonaceous matrix and (2) the uptake of dissolved gold by the carbonaceous leach residues. A critical review is presented of the published information from various parts of the world pertaining to the nature of the carbon-containing components of these ores and their different roles in the gold extraction process. Included in this paper are new results based on the authors' research on carbonaceous ores from the Prestea goldfields of Ghana. Methods for isolating and characterizing the carbon-containing materials are given and a discussion is presented of the interaction of the carbonaceous ores as well as the fractionated components with aurocyanide solutions. Emphasis is on basic physico-chemical phenomena, investigated with the aid of X-ray diffraction, infrared spectroscopy, adsorption, and electrophoretic mobility studies.

Jan 1, 1984

By Marcel Daly

THE writer has devoted a number of years to practical operations and to the study of geology in the oil fields. In consequence, he has been brought to investigate the theories advanced to account for the accumulation of oil and gas in commercial deposits. It is the result of these investigations and his personal conclusions that he wishes to sum up in this paper. The writer is an advocate of the organic origin of petroleum found in pools. He has been led to believe that the present theories of oil and gas accumulations are incomplete and, in certain respects, incorrect, although they may embody certain elements of truth; that the forces that are called upon to explain the movement are only secondary forces in the process, and insufficient, by themselves, to cause this movement; and that the phenomenon of accumulation is of much larger order than heretofore admitted and bears an intimate relation with the general as well as with the local deformations of the crust and is a direct consequence and a mechanical effect of these deformations to which the term "diastrophic" has been applied. As a complement to this theory, the writer offers a new interpretation of the "rock pressure" and of the mechanism of the "sealing up" of this pressure in oil and gas pools.

Jan 7, 1916

By A. E. Moss, J. K. Gustafson

MEASURED in terms of ore tonnage, the New Quebec and Labrador iron ore fields promise to rank with the greatest iron ore districts of the world. Over 400 million tons of high-grade ore for direct shipping have been discovered to date. Much greater amounts of lower-grade beneficiating ores are indicated by outcrops. Many hundreds of square miles of iron formation await testing. By 1954 iron ore will begin to move towards American blast furnaces, and shortly thereafter the annual rate of production is expected to reach 10 . million tons. To bring this vast project into being over $200,000,000 will have been spent for exploration and development, mining equipment, hydro plants, townsites, the building and the equipping of . a 360-mile railroad, and the construction of docks and ore-handling facilities. The most important iron ore deposits are located over 300 miles from tide water, see frontispiece and also Fig. 1. The frontispiece shows principal sources of iron ores and manganiferous iron ores for the U. S. and Canadian steel industry, and the major smelting districts are shaded on the map. No navi- gable rivers lead into the interior. When work was . commenced on this project there were no roads, no railroads, no communication ,system, no inhabitants, and no adequate maps either topographical or geological. The geological field season was limited to approximately 100 days per season. The obstacles facing this enterprise were many and varied. Its success will be due to the integrated team work of people of diverse skills. Explorers, Indian guides, prospectors, geologists, surveyors, mechanical, civil, electrical, and mining engineers,

Jan 1, 1954

By R. Gibala

Internal-friction measurements on hydrogen-charged iron over the temperature range 4° to 300°K are reported. Two relaxation peaks, the hydrogen Snoek peak at 48 °K and the hydrogen cold-work peak in the range 145" to 2200K, are observed at 80 kc per sec. The effects of hydrogen-charging, aging, and deformation on the internal-friction results are determined and are used to show evidence of partitioning of hydrogen between solid solution and dislocations. The hydrogen-dislocation binding energy is estimated from the behaviors of the relaxation tiwzes and relaxation strengths of the Snoek peak and the cold-work peak. Its value is approxi,mately 6400 cal per mole. MANY investigators have demonstrated the usefulness of internal-friction measurements in determining the manner in which interstitial impurities interact with dislocations in bcc metals. Part of this success has resulted from the existence in bcc interstitial alloys of two anelastic relaxation peaks—the Snoek peak' and the cold-work or Koster peak2 (designated hereafter by SP and CWP, respectively). The SP has its origin in the redistribution of interstitials in solid solution among sites made energetically nonequivalent by an applied stress. The rate at which the redistribution occurs, measured by the relaxation time for the process, is related in a simple way to the diffusion rate of the interstitial in the free solution. The relaxation strength is proportional to the concentration of interstitial in solid solution. The CWP appears to have its origin in the relaxation of an interstitial-dislocation complex for which the relaxation time at a given temperature is much longer than that for the SP. The relaxation strength depends strongly on the concentration of interstitial and the amount of deformation at relatively low concentrations and deformations.2-8 From the dependence of the relaxation strength on interstitial concentration, the SP and CWP may serve as measures of the concentrations of interstitials in free solution and bound at dislocations, respectively. Thus their behaviors have been used to investigate interstitial-dislocation interactions in Fe-C, Fe-N, and several refractory metal systems.'-' However, the Fe-H system has not been studied extensively,? even though disputes in recent years over the mechanism of hydrogen embrittlement in steels involve argument over the extent to which lattice hydrogen and hydrogen-dislocation interactions play an important role.?-'' Previous work on Fe-H indicates the internal-friction behavior to be qualitatively consistent with that for other systems. Apparently, both a SP and a CWP are observed in the temperature ranges 30" to 50°K and 100°to 140°K, respectively (at 1 cps). However, there is neither sufficient nor accurate enough information to identify convincingly these peaks with their supposed counterparts in other systems. Nor have there been any attempts to make quantitative use of these peaks to study hydrogen diffusion, aging, or interaction processes. In this paper, an attempt is made to obtain more complete information on internal friction of hydrogen in iron than presently available. Internal-friction measurements in the range 4° to 300°K on hydrogen-charged iron show that the two peaks discussed above are in fact the hydrogen SP and CWP. Several effects of hydrogen charging, aging, and deformation on these peaks are observed and are used to determine the partitioning of hydrogen between solid solution and dislocation sites in iron. EXPERIMENTAL Materials. The starting material for this investigation was a high-purity iron supplied by National Research Corp. as a 1-in.-diam rod. The following analysis was given (inwt pct): C, 0.004; N, 0.0003; 0, 0.007; P, 0.002; S, 0.005; Si, 0.006; Mn, 0.001; Cu, 0.002; Ni, 0.005; Cr, 0.001; Mo, 0.001. After an initial vacuum anneal (-5 XTorr) at 700°C, the rod was cold-

Jan 1, 1968

By John V. Beall

THIS is not simply the story of how a water filled shaft was developed into a million-ton- a-year producing mine in the space of four critical years, although it is reason enough for telling it, but it is also the saga of an engineering achievement in which knowledge nurtured by years of experience in coal and ore mines was blended together and the best from each type of mining selected. The entire system of mining was detailed on maps by the mining engineering department before the shaft was unwatered, and subsequent development followed these plans nearly to perfection. The selection of machinery was particularly critical as it was necessary to push production from only a few headings in the early stages of development and metal mine machinery was being used in a coal panel-system of mining.

Jan 12, 1950

By Edward Keller

About a dozen years ago the art of bessemerizing copper- * matte, brought to these shores from France, was first established at the smelter, in Butte, Montana, of the Parrot Silver and Copper Company, which had bought the process from Mr. Manhks, the inventor. Through the efforts of Mr. J. E. Gaylord, general manager, and Mr. A. J. Schumacher, snperintendent,, assisted by an able staff, the new method rapidly underwent, at the Parrot establishment, an evolution towards higher perfedion, and within a few years its success and its advantages were so marked that all the great works in the west followed in the footsteps of this pioneer. The converter-process has now practically superseded the reverberatory-process in this country. The latter will undoubtedly, in a not very distant future, be relegated to metallurgical history. The writer has availed himself of what was perhaps the last chance to make comparisons of the two methods, working practically on the same material on an extensive scale, the reverberatory process being that of the Baltimore Copper Smelting and Rolling Company,* while the converter-process is that of the Anaconda Copper Company—both using the matte from the latter company's works in Anaconda, Montana. For the greater portion of the material considered in this paper, the writer is indebted to the two companies. In order to understand the difference of behavior of the several elements, and the difference of the copper produced in the two processes, it is best to study and follow those elements

Jan 1, 1899

By A. B. Kinzel

Precise knowledge regarding the effect of heat treatment on the properties of steel has made possible the detailed specifications and instructions covering optimum heat-treating temperatures and practices that are in current use. A distinct contrast is presented by the metallurgical treatment of steel adjacent to a fusion weld, as such steel is subjected to each temperature from room temperature to fusion temperature, and cooled at a rate that is not generally controllable but is predetermined by the nature of the assembly to be welded, the kind of welding used, and the surrounding conditions. This is true regardless of the type of fusion welding: oxyacetylene, electric arc, thermit or flash resistance. Therefore it seemed desirable to investigate the effect of this metallurgical treatment on the characteristics of carbon steels commonly used for welding, by a detailed study of metal subjected to each temperature range; i.e., each heat-affected zone. Oxyacetylene welding was chosen for the investigation because of the experimental facility of accurately segregating and studying each temperature zone. The nature of the zones produced by other types of welding is the same. The difference is primarily a matter of dimensions of each of the temperature zones involved. The advantages and disadvantages of the extent of the zone are of prime moment, and are discussed after the presentation of the detailed zone study. No mention is made of the fused metal proper, as this has been the subject of much published research and the nature of the solidified metal is fairly .ell known. General Method The scheme of procedure in the work herein reported involved the testing of the metal of each temperature zone adjacent to the weld in so

Jan 1, 1935

By A. B. Kinzel

Precise knowledge regarding the effect of heat treatment on the properties of steel has made possible the detailed specifications and instructions covering optimum heat-treating temperatures and practices that are in current use. A distinct contrast is presented by the metallurgical treatment of steel adjacent to a fusion weld, as such steel is subjected to each temperature from room temperature to fusion temperature, and cooled at a rate that is not generally controllable but is predetermined by the nature of the assembly to be welded, the kind of welding used, and the surrounding conditions. This is true regardless of the type of fusion welding: oxyacetylene, electric arc, thermit or flash resistance. Therefore it seemed desirable to investigate the effect of this metallurgical treatment on the characteristics of carbon steels commonly used for welding, by a detailed study of metal subjected to each temperature range; i.e., each heat-affected zone. Oxyacetylene welding was chosen for the investigation because of the experimental facility of accurately segregating and studying each temperature zone. The nature of the zones produced by other types of welding is the same. The difference is primarily a matter of dimensions of each of the temperature zones involved. The advantages and disadvantages of the extent of the zone are of prime moment, and are discussed after the presentation of the detailed zone study. No mention is made of the fused metal proper, as this has been the subject of much published research and the nature of the solidified metal is fairly .ell known. General Method The scheme of procedure in the work herein reported involved the testing of the metal of each temperature zone adjacent to the weld in so

Jan 1, 1935

By J. W. Halley, G. L. Plimpton

BECAUSE of the two distinct stages in the solidification of rimmed steel, segregation in the rimmed ingot is more complex than that in the killed or semikilled ingot. In the earlier stage, chemical reactions, resulting in evolution of gas and vigorous stirring of the metal, effect a degree of negative segregation unique to rimmed steel. The composition of this zone constitutes the principal quality advantage of this type of steel. In the later stage of solidification, after the evolution of gas has ceased, the segregation follows the general pattern of a more completely deoxidized steel. However, the composition of the liquid remaining after the first solidification stage varies markedly from that of the original melt, some constituents having been partially removed as reaction products while the concentration of others has been intensified by rejection from the metal solidifying in the first zone. The aim, from the standpoint of segregation, in rimmed steel of high quality is to effect a maximum negative segregation in the rim zone without excessive concentration of undesirable elements at the center of the ingot. To achieve this aim, the composition of the melt may be varied and the furnace and pouring practice may be adjusted within certain limits. It is the purpose of this study to discuss segregation in rimmed steel from the standpoint of the mechanisms that produce it and to survey the phases of open-hearth practice that influence those mechanisms. MECHANISMS PRODUCING SEGREGATION The mechanisms that determine the degree of segregation in the rimmed ingot are closely interrelated, making it difficult to select the primary factors and to determine a satisfactory order for presenting them. For instance, the question of sulphur segregation is relatively simple, since sulphur is not directly involved in chemical reactions in the ingot; but its concentration in the rim zone is dependent not only on its original analysis in the melt, its segregation coefficient, and the freezing rate, but also on the rate of its removal from the impure film on the solidifying surface. This washing action involves all the factors (such as freezing rate, the carbon-oxygen product, pressure, etc.) that determine the rate of gas evolution and hence the efficiency of film removal. Sulphur distribution between the rim and core is affected by the volumetric ratio between the two zones, and its segregation in the core is a function not only of the freezing rate of the core but also of all the foregoing factors that determine its concentration in the metal when solidification of the core starts. To simplify the presentation, it is proposed to treat the mechanisms affecting segregation independently in this section, reserving a discussion of their over-all effects for the section in which actual segregation data are given. The factors affecting segregation will be treated in the following order: (I) differential solidification, (2) removal of constituents as

Jan 1, 1944

By Carl Samans

THE attention of physicists and metallurgists has been directed toward the study and explanation of the deformation textures in metals for the past 15 years. In 1920 N. Uspenski and S. Konobejewski1 were first able to show that the symmetrical X-ray diffraction effects that had been previously reported by E. Hupka2 and others in metal foils were caused by a directed arrangement of the crystallites. Since then, the systematic study of textures resulting from the application of the pure forces of tension or compression to polycrystalline materials hag been supple-mented by many investigations on deformed single crystals, which have greatly added to our knowledge of deformation. However, despite the valuable information secured from these comparative studies only four investigations upon cold-rolled single crystals of any of the face-centered cubic metals have been reported in the literature. This lack of quantita-tive data is especially unfortunate because of the much greater practical significance of rolling textures and their effects in both cold-rolled and annealed materials. This investigation was undertaken for the purpose of specifying the deformation of rolled single crystals in the hope that such information might later facilitate the explanation of polycrystal-line textures.

Jan 1, 1934

By B. D. Cullity, A. Freda

It is well known that deformation by cold drawing or swaging produces a kind of preferred orientation called fiber texture in metal wires. Such textures have been extensively studied by means of X-ray diffraction, chiefly by techniques in which the diffracted X-rays are recorded photographically. This paper describes some results obtained with a new method, involving the use of a diffractometer. X-RAY METHOD Since the pole figure of a material having a fiber texture is symmetrical about the fiber axis, there is no need to present the entire pole figure. Instead, texture data can be summarized by means of a curve showing the variation of pole density along any meridian of the pole figure, if the north-south axis of the latter is made parallel to the fiber axis. The position of a pole on the meridian is specified by the angle 9 between the pole and the fiber axis (wire axis). The X-ray method1 used here to measure pole density as a function of 9 actually consists of two methods, referred to as A and B. In method a, X-rays are reflected from the wire surface. Pole densities can be measured by this method from O = 90 deg down to a limiting value which is dependent on the Bragg angle 8 and is typically of the order of 30 to 40 deg. Method B involves diffraction from the wire cross section and covers a range of 0 values from 0 up to an angle sufficient to overlap the measurements made by method A. By a combination of the two methods, a complete pole-density curve can be obtained. However, method A alone, which requires no specimen preparation other than etching, can often reveal enough of the pole-density curve to provide complete information about texture components. Both methods require that the measured diffracted intensities be corrected for changes in absorption and diffracting volume with changes in 9. A11 intensities I reported in this paper are corrected diffracted intensities; they are propor-

Jan 1, 1960

By S. E. Craig

UPON entering the Uranium Field it was a pleasant surprise to find almost absent two factors that have always been a problem to the lead-zinc miner: 1) milling cost per ton, and 2) transportation cost to the milling site. Another interesting condition was the fixed price for the product. Under such conditions it seems rather simple to calculate the economics of a mining venture when grade and tonnage of a uranium ore deposit is known. That is assuming, of course, there is a market for the ore. It has been quite generally assumed by operators that a guaranteed price carried with it a guaranteed market, a subject about which there has been a great deal of discussion in the past several months. The fixed price for uranium in crude ore, calculated to U3O8, varies only slightly in value per pound from rather low grade ore to rather high grade ore. It is by taking advantage of this slight variation in price per pound in certain ranges that miners and shippers may increase substantially the monthly returns from ore shipments.

Jan 7, 1958

By Samuel B. Christy

" The man is always greater than his work." The training of the men who are to develop the mineral resources of the world is the most important problem connected with mining engineering. It becomes ever more important to civilization as the mineral wealth of the earth approaches exhaustion. I have therefore decided to consider a few of the more important problems arising in the training of the mining engineer, and especially those arising in America. , The Peculiar Nature of Mineral Wealth. Mining and Agriculture are the two fundamental arts. Without the latter our existence would be precarious; without the former, our civilization impossible. Agriculture furnishes that regular supply of food and raiment which leads to the growth of large communities in which cultivated leisure first becomes possible; while mining furnishes the metallic thread from which is woven that complex fabric we call civilization. But in these two arts the conditions for success are widely different. Most of the crops that the farmer reaps may be harvested year after year, and the proper fertilizers being added, he may continue the annual harvest indefinitely, while, as a result of cultivation, his farm becomes yearly more valuable. But the crop the miner reaps can be harvested but once in the history of the race. Our mineral wealth has taken unknown ages to mature in the bosom of the earth. The ripened fruit can be plucked but once. There are no fertilizers for worked-out mines. It never pays to work over a mine that has been

Jan 1, 1906

By George Sachs

THE process of recrystallization has not as yet been explained satis-factorily. Some definite conclusions could be drawn from recent investi-gations, such as, for example, that recrystallization is a process of nucleus formation and crystal growth 1and that the orientations of the nuclei correspond to some fragments of the original crystals, which have been considerably distorted during deformation.2 There are, however, a number of metals and alloys crystallizing in the face-centered cubic system, which form a particularly simple orientation if recrystallized as a sheet.3 Such a sheet is almost a single crystal with the cubic axes parallel to the rolling, transverse, and normal directions of the sheet. This preferred cubic or (100) orientation of the recrystallized sheet has been considered to be very different from the rolling structure of the same metals,4 but there are two reasons why this last supposition remains open to controversial discussion. The first reason is academic: In practically all cases except the one mentioned above, close correlations and similarities between rolling and annealing orientations have been observed; for instance, in iron and steel sheet.6 Secondly, no deformed metal actually forms a-simple orientation. In any thoroughly investigated case a number of different orientations and considerable scattering or deviations from the ideal orientations have been found., It is generally true that investigations on single crystals have shown that a definite orientation is approached in stretching or in compression of an originally undisturbed crystal.7 In the special cases, however, where the initial orientation was close to an important crystallographic direction that differed from the final "ideal" orientation, the resulting orientation changed very little by deformation, staying somewhere in the vicinity of the initial orientation." Such deviations

Jan 1, 1940

By H. S. McQueen

The insoluble-residue method for the examination and correlation of limestones and dolomites, or other sedimentary rocks containing calcium and magnesium carbonates, originated and was developed in the laboratory of the Missouri Geological Survey. The numerous and ever-increasing problems in the field of applied geology, and the need for a tool or aid in the solution of them, led to experimental work with samples collected from deep wells, in the early part of 1924. The success attained, almost at the outset, with this method was so great that the method has now been developed from the state of the experimental to the realm of large-scale, every-day routine. In a previous paper the writer1 described the procedure in detail and the characteristics of the residues obtained from certain Paleozoic formations in Missouri. The purpose of the present paper is to discuss the economic application of the insoluble-residue method. Developmental History Within the Ozark region of southern Missouri the geologic column consists of Lower Ordovician (Canadian of Ulrich) and Upper Cambrian formations, which are composed mainly of dolomite with subordinate amounts of sandstone, shale and limestone. Chert is found to some extent in all except one of the dolomite formations. The stratigraphy of the region is complex because the dolomites have lithologic similarities, fossils are few and often poorly preserved, and identifiable horizons within the comparatively thick formations are not common. Although considerable stratigraphic work of an areal nature had been done for a period of many years by the Missouri Geological Survey, the detailed geologic succession had not, until a few years ago, been systematically worked out. The problems of subsurface stratigraphy were even more complex. This region constitutes the main ground-water province of the State of Missouri and within it wells of varying depths are drilled in order to obtain supplies of ground water. In the work of the State Geological Survey in connection with the drilling of water wells for public supplies * Published with the permission of the Director, Missouri Geological Survey and Water Resources. Manuscript received at the office of the Institute Feb. 20, 1936. Assistant State Geologist of Missouri; Missouri Geological Survey, Rolla, Mo. References are at the end of the paper.

Jan 1, 1937

By Joseph B. Story, John T. Clarke

A modification, of the Kelvin bridge using an inductor was used to measure the conductivities of molten sodium chloride, calcium chloride, and mixtures thereof. A capillary-type four-lead fused quartz dipping cell was constructed. The effect of a small amount of potassium chloride on the conductivity of the melt was determined. IN the electrowinning of sodium and chlorine from sodium chloride in Downs cells, calcium chloride is added to the sodium chloride in an approximately equimolar amount to permit cell operation at a lower temperature. This lower temperature improves current efficiency and ease of operation, but decreases voltage efficiency by decreasing the electrical conductivity of the melt. A knowledge of the electrical conductivity of the Downs cell melt is necessary to the understanding of Downs cell operation, for the IR voltage drop across the melt is responsible for a significant part of the electrical power consumed by the cell. The work of previous investigators on fused sodium chloride-calcium chloride mixtures was reviewed from the standpoint of consistency with the results of others on the conductivities of the pure constituents. The electrical conductivity of pure fused sodium chloride has been established with accuracy by Van Artsdalen and Yaffe,1 by Edwards, Taylor, Russell, and Maranville,2 and by Lee and Pearson.3 It has also been studied by a number of other investigators.4-13 The best values for calcium chloride are believed to be those of Lee and Pearson,3 since the sodium chloride and potassium chloride conductivity values given by them check the best literature values. A number of other investigators have also reported values for calcium chloride.'-"."' Electrical conductivity data for fused sodium chloride-calcium chloride mixtures have been reported by Sandonnini,12 Vereshchetina and Luz-hnaya,18 Ryschkewitsch,11 Barzakovskii,5 and Alaby-shev and Kulakovskaya.15 Sandonnini reports no data at temperatures lower than 850°C. The conductivity values reported by Vereshchetina and Luz-hnaya, by Ryschkewitsch, and by Barzakovskii for pure sodium chloride and for pure calcium chlor- ide vary somewhat from the literature values believed to be best and the sodium chloride-calcium mixture data of these authors and of Alabyshev and Kulakovskaya (who give no data for the pure compounds) show significant variations. In view of these facts, it seemed that an investigation of the electrical conductivities of fused sodium chloride-calcium mixtures would be worthwhile. Apparatus Bridge System—The bridge used,in this investigation is diagrammed in Fig. 1. In general, the elaborations of this bridge over the simple Wheatstone bridge were for the purposes of a) eliminating lead resistances or making them accurately measurable, and b) eliminating major capacitative and inductive effects or balancing them against each other. Lead resistances in the lower arms of the bridge were kept as low as possible by making the leads short and of low resistance wire. This could not be done in the cell arm of the bridge because of the remoteness of the cell from the other bridge components and because of the high-resistance nickel or chrome1 wires used in the cell. Since maximum sensitivity is attained when the resistances of the four arms of the bridge are equal, 50-O resistors were used in the lower arms of the bridge when fused salt conductivities were being measured, and 1000-O resistors were used when the cell was being calibrated with normal aqueous KCl solution. The cell resistance was of the order of 50 ohms with fused salts and of the order of 1000 ohms with normal aqueous KC1 solution. The resistors used were non-inductive and accurate to 50.05 pct (General Radio Co. Types 500-C and 500-H). The lead resistance between point A in the cell and point E at the measuring resistor was eliminated by using the kelvin bridge principle; that is, the voltape drop across the lead from point A to point E was divided between the cell arm of the bridge and the measuring arm of the bridge in proporation to the resistaxes in the lower arms of the bridge.

Jan 1, 1958

By E. C. W. Perryman

The recovery of X-ray line broadening, hardness, and electrical resistivity from cold worked AI-Mg alloys has been investigated. The results, together with those from density measurements, suggest that magnesium atoms freeze in the excess vacancies formed by cold working, and that this affects the climb of dislocations during the recovery process. PREVIOUS work1, " has shown that while 1 pct Mg increases the activation energy for recrystalliza-tion, it decreases the activation energy for the recovery of mechanical properties and decreases the subgrain size both after cold working and annealing. A similar result has been reported by Varley2 for an A1-2 pct Mg alloy. With plastic deformation at high temperatures, McLean and Farmer' and Rachinger have found that magnesium appears to retard the motion of dislocations and, furthermore, they find little or no effect of magnesium on the size of subgrains formed during high temperature deformation. In view of the apparent contradictions as to the effect of magnesium on subgrain size, the recovery process in Al-Mg alloys has been investigated more thoroughly by studying the annealing out of X-ray line broadening, hardness, and electrical resistivity from alloys cold worked at room temperature. Material Used—The chemical analyses of the alloys are given in Table I. Fabrication—The material used was cold rolled 20 pct at room temperature, the grain size prior to the last cold rolling operation being similar to that used in previous work; i.e., 230. The experimental procedure for annealing, determination of X-rav half-veak breadth. hardness measurement, electEica1 resistivity, and density and metallographic examination was exactly the same as previously described." Variation of X-Ray Half-Peak Breadth with Annealing Time—Isothermal annealing curves at 100°, 200°, and 250°C were obtained for material cold worked 20 pct. The half-peak breadth of the (333) Ka, line directly after cold working is shown as a function of magnesium content in Fig. 1. Only with the 2.87 pct Mg alloy was overlapping of the a, and n.. reflections observed to any appreciable extent. To separate these, Rachinger's method' was used. Typical isothermal annealing curves are shown in Figs. 2 and 3 for 100" and 200°C, respectively. These curves are similar to those obtained previously for super-purity aluminum except that the

Jan 1, 1957